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Engine Oil - A slippery subject Part 2

mznmzn Member Posts: 727
Here's the spot for all your engine oil questions
and answers. If you're looking for Part 1 of this
topic, it's right here.

carlady/roving host


  • ghtrapghtrap Member Posts: 26
    Well, let's start the oil topic #2.

    I was a die hard 10w-30 user until about a year ago and finaly gave up and went with 5w-30 like my owner's manuals said for both my Accord and Explorer. I actually picked up some gas mileage, but I do believe the greatest benefit to the engine is upon start-up - flows better in a cold engine.

    Even though I have nothing against it, I still am too much of a die hard to go with synthetic. I'm one of those who uses Quaker State dino and changes every 3,000 miles. My engines last very well.
  • scherfscherf Member Posts: 8
    After reading the last two posts, I'm inclined to agree on 5W-30. I was surprised to hear that so many manufacturers suggest that viscosity. I haven't made up my mind on synthetics, though. I've read previous posts suggesting that synthetic users have to crank their engine less during the winter (better start up). I wonder if the difference is as pronounced with a 5W-30 weight oil as a 10W-30... I don't exactly live north of the artic circle (Ohio), so I wonder if this is a moot point.

    I've always changed at 3-4K also, depending on manufacturer recommendations. Don't know if it's really needed, but I'm not going to second guess the engineers who designed my car.

    ghtrap--just out of curiosity, do you notice better starting all year or just in winter?
  • inkyinky Member Posts: 370
    I noticed that OLDs recommends 10w30 for the intrigue with 3.5 l. IT is posted on the oil filler cap. MOst other cars do recommend 5w30 and that is what I use in my Lexus ES300 and Honda Odyssey. If you want quick lubrication at start up to reduce engine wear and you do not drive near redline continually a good 5w30 should do the trick. I would admit that 5w30 would not lubricate properly say a Honda Civic that goes to high rpms a lot in warm summer months.
  • btroybtroy Member Posts: 92
    5-30 and 10-30 will have the same viscosity under high temperatures. The only difference is in low-temperature viscosity.
  • rs_pettyrs_petty Member Posts: 423
    But I believe one reason 5w-50 is not recommended by the manufacturers is it is only available from a few companies and in synthetic. They have to conform to a wide consumer base. I wonder if the engine would even know if it had 5w-30 or 5w-50. Perhaps though on second thought it would create too thick of an oil layer in the lubrication system causing oil pressure to be too high leading to seeps & leaks and possibly reducing gas mileage.
  • SporinSporin Member Posts: 1,066
    Best of both worlds? Opinions and experiences?
  • scherfscherf Member Posts: 8
    rs_petty: I'm inclined to think that you are right about that being too think. That's the same as 20W-50, and my guess is that tolerances are probably too tight. As per my previous posts (and answers to it), it looks like most of the manufacturers are getting away from that heavy stuff.

    sporin--I don't think I would ever use a synthetic blend. I checked out the numbers, and they are virtually identical to conventional oil. I've seen posts here where the amount of synthetic oil in the blends is MAX 25% (some only 10%--I know that number for sure). You'd be economically better off to buy a quart or two of synthetic for your next oil change and mix it with the conventional oil (they're all fully compatible, but you could get Castrol Syntec and Regular Castrol, if it gives you greater peace of mind), and you'd get a higher % synthetic (that's all the manufacturer does--there's nothing special about the blends. Just more money.

    My question--anyone know anything about Motorcraft oil? It seems to be more expensive, and I wonder if it's actually made by Ford or if they just slap their name on it.
  • ccotenjccotenj Member Posts: 610
    in my bimmer. mobil 1. i was amazed the first time i poured syn out of a bottle. the stuff flows like water.
    i noticed when i put syn in my f150 that it just "sounded" better at startup. could be a placebo effect.
    comment on syn blends. frankly, worst of both worlds, imho.
  • thoughtthought Member Posts: 1
    Can anyone share their long term experience with using synthetic in a turbocharged engine? I'm considering changing from dino to Mobil 1 in my '94 Volvo 940 which just turned over 100k. I am especially interested in frequency of synthetic oil changes for anyone with a turbo. I plan to run Mobil 1 with the A-C Delco Ultra-guard Gold filter in my new Honda Odyssey LX and change oil every 7500 mi. (Thanks for the filter suggestion Inky!)
  • ghtrapghtrap Member Posts: 26

    I can't actually say that I can tell the difference between 5W-30 and 10W-30 upon start up whether its summer or winter, I just believe in the theory that the 5W-30 should flow better to the upper portions of the engine when cold.

    I live in Kansas, so I don't even have the winters that you do in Ohio. You may or may not be able to tell a start-up difference with the 5W-30 at very cold temperatures.
  • inkyinky Member Posts: 370
    I switched to mobil one 5w30 from conv 10w30 and get 2 mpg better in very similiar driving-almost identical. It also starts easier. I will run for 6,000 miles to get my money out of it.
  • SporinSporin Member Posts: 1,066

    I am figuring to go to Mobil 1 5W-30 at 20k miles, with 7500± mile changes. car is a 99 Passat 1.8 Turbo. Owners on and have reported...
    • better mileage
    • easier startup in cold weather
    • cooler running temps

    ...when switching to Synthetic.
  • treyh1treyh1 Member Posts: 34
    How much oil is normally used between changes? I've got a 5 qt capacity & when I pour up the old oil to recycle it I usually get just a little over 4 qts. I change every 3500 miles; the truck is a 3.0 Ranger with about 35,000 miles on it. Is this about average for oil usage?
  • ccotenjccotenj Member Posts: 610
    it's normal for ford trucks to burn oil... i don't know why, but everyone i know (plus myself) who owns one says they do, and the service rep at the dealer said that it's normal....
  • div2div2 Member Posts: 2,580
    Most of today's carmakers don't consider oil consumption excessive until it exceeds one quart in 1000 miles. No way would I worry about one quart in 3500. You should be OK for many thousands of miles to come.
  • ruking1ruking1 Member Posts: 19,826
    I have a 94TLC that uses one quart or so in 14,000 miles. It has app 65,000 miles on it.
  • reanimator1reanimator1 Member Posts: 4
    Hey everyone,
    As far as the choice between the two viscosities, I thought the 50 weight would be better in hot temperatures/long hard driving conditions. Since the 50 refers to the high end temps. I have not read or heard of any manufacturers recommending it but it seemed logical to me. 4 cylinder engines do have to work harder, get hotter, so should need more protection. Since I am not an expert on motoer oils, I will defer to those who know more. But I do think that a synthetic 5W-40 at least should be a good bet in a new engine (I just turned 850 miles on my 2000 Tiburon). I Would appreciate any additional comments on this subject, maybe someone who has actually tried 5W-50. Or maybe a mechanic.
  • lmvinelmvine Member Posts: 2
    Use what your manufacturer recommends. Too wide a viscosity range is bad because the extra polymers added to make wide viscosity range can breakdown and cause problem per oil FAQ:
  • donbaadonbaa Member Posts: 4
    My theory is:
    Synthetic oil is known to flow much better at low temperatures and therefore there has to be less wear during the warm up.

  • scherfscherf Member Posts: 8
    I don't think anyone would argue the point that synthetic is better at start up. It is better for everything. The real question is--is the cost justified? I'm still trying to make up my mind personally. I mean, I've always changed oil according to manufactuer recommendations and have never had an oil related problem. If you use synthetic, your engine might last much, much longer. But if all the other parts on the car are falling apart first, is it really worthwhile? Dino might make it last to that point also. That's the dillemma...
  • edwardh3edwardh3 Member Posts: 6
    if syn oil stays in your car a long time the acid from the combustion process builds up.
    Changing regular oil gets rid of it.
  • donbaadonbaa Member Posts: 4
    Consumer Reports tested several motor oil including synthetics in NY taxi cabs. Reported about 1997. Synthetic fared no better than other top oils. But, the test was conducted with very long running times, therefore few cold starts. My conclusion is the only advantage (unproven) is helping reduce wear during cold starts and warm up.
  • ruking1ruking1 Member Posts: 19,826
    Further on in the same article, they say that they couldn't complete the tests for synthetic due to mechanical failure of the vehicle not related to the oil.

    With the extreme oil changes at 3k as advocated by myth, marketing, fear, etc, the synthetic is clearly not worth the extra cost. However keep in mind that you are using 2x to 5x the product. So if you go from 7.5k to 15k between oil changes, it starts to offer scale of economics also.
  • edwardh3edwardh3 Member Posts: 6
    For the cars that have the oil change puters, like MB and I think some GM trucks -what change interval is called for?
  • SPYDER98SPYDER98 Member Posts: 239
    I have been using synthetic now for about 7000 miles in my turbo eclipse. I've done 2 oil changes at 4000 mile intervals and I honestly do not see a difference in anything. Except the extra 20 bucks I dish out at the shop.
    The synthetic is turning dark just as quickly as conventional was.

    But I do think the word synthetic sounds better than the word conventional.
    Don't ya think?
  • sdc2sdc2 Member Posts: 780 interview with a racing team some years ago when synthetic oil was still relatively new, and they talked about their experience. Before with conventional oil they had to rebuild their engines after ever race. The first time they used Mobil One, they tore down the engine and found everything was within original specs. After that they found they could go four or five races between rebuilds.

    That is a pretty significant difference. The question is, is it relevant to our situation? None of us rev as high or run at the temps racers do. And they don't give a rip about cold start attributes.

    I can tell you that I decided to go to synthetic about 12-15 years ago, and none of my vehicles have EVER needed to add oil between changes. Some of those vehicles were well over 150K miles.

    I just don't feel that $20 for an oil change (I change my own) is too much to spend every 3,000 miles, when you look at the expense of the vehicle. Conventional oil would save me a whopping 0.4 cents per mile. AAA says we pay something like 35 cents per mile to operate a vehicle, so the "expense" of synthetic is just not that burdensome.

    And finally, I do feel that the cold start thing is big here in Minnesota, where occasionally I have to start at -20F or lower. If you have never had the pleasure, your car sounds like a coffee can full of rocks at that temp, until it warms up after 15 minutes or so :)
  • rs_pettyrs_petty Member Posts: 423
    12,000 miles annual
    conventional oil change - 3000
    synthetic oil change - 6000
    6 qts per change

    Syn: 6 x $3.65 x 2= 43.80
    Con: 6 x $1.25 x 2= 30.00

    Less than 15 bucks over the year. My view is that synthetic may not be noticeable when an engine is new, but at 60-100k I hope to see engine performance remain rather than start to taper off because of worn engine parts. Same could be said for using synthetic lubricants in other mechanicals like trans, rear-end, PS pump. I need about 10 years of reliable service out of my vehicle.
  • dhanleydhanley Member Posts: 1,531
    With conventional oil, I stick to 3K change intervals. With synthetic, I feel that I can do 6K change intervals. That about cancels out the extra cost of the synthetic due to fewer visits for oil change. I do have to add about a quart between, typically. It still costs me a bit extra, but, as a previous poster said, if it gets me one more month out of my car, it's worth it. I put about 40K per year on my car, and I plan to take it to 150K miles or so. The only reason I've worried about it is that I expect the car would get to 150K miles on regular oil with no problems either. Still, since the extra cost is so small, I don't worry about it too much.

  • tauberjtauberj Member Posts: 61
    I've used Mobile 1 5W-30 in my 94 Jimmy since it's first oil change with no problems. The vehicle now has 75K miles and runs like new. In 94, GMC provided the first oil change free using Mobil 1. My decision was based on the fact that I tow a pop-up camper during the summer months and tend to drive at 75 mph, even when towing. I think the greatest benefit in my case is that under high heat conditions, I know I can count on synthetic oil. I change my oil every 5000 miles. BTW, I usually can find the oil on sale for about $3.50/quart or buy it from a wholesale club for $21.50/6-pack. I get GM filters for $1.99 on sale in K-mart. Thus, since I change my own oil, an oil change costs about $20 with tax. For my 2000 Silohuette, I'll use dino oil every 3000 miless only because it looks too difficult to change it myself. I will also use this vehicle to tow the trailer.
  • rs_pettyrs_petty Member Posts: 423
    Have any facts/studies been done on normal cars/trucks? What happens to oil when a car is not used regularly on weekends or is only used on
    weekends? What effect does moisture and acids play on oil life? At what point does the oil/filter combination lose the ability to protect the engine? Is it 3k or is it closer to the factory recommended changes approaching 6k or 7.5k (some are even longer)? Posts on other topics have said that oil life, measured by contaminate suspension, is around 5k. I'm not sure this is definitive and is certainly effected by driving conditions. If suspended contaminates are the real evil causing oil changes then logically air quality conditions would effect this - then why is stop/go city driving touted as a major reason for oil change - seems to me it would be harder on transmissions (hince ATF) than engine oil, but I don't see or hear about 3k ATF changes. I use to change air filters with oil changes, but factory schedules are showing 15k or a year between changes. My understanding of combustion engines would lead one to say that a dirty/inefficient air filter allows more dirt into the engine than anything else (the only other avenue is internal wear of components).
    There is suppose to be less wear with synthetics
    so therefore there should be less contaminates in
    the oil with synthetic. Should air filters be
    changed more often? I ask these questions because
    of my experience with the Army's oil analysis
    program. The two major reasons for the program
    were to get an early identification of engine
    failure either through component wear or dirty air
    filters. You did not want an analysis returned
    indicating dirty air filters (trust me). Component wear ID allowed better logistics planning, service schedules and ultimately better readiness. What I am trying to think through on this post is a 3k oil change with conventional oil better than 7.5k oil change with synthetic oil. If I believe the 3k oil change story then logically I should look at more frequent changes for other fluids that also get contaminated. If I believe the factory recommended schedules, but just want to use IMHO a better quality lubricant then I should also get a satisfactory service life. I'm not sure there is an absolute answer to this question, but I love my truck and want to keep it that way.
  • b67kb67k Member Posts: 2
    I noticed that for MODEL YEAR 2000 you can choose a HIGH PERFORMANCE LUBE. PKG.
    on the TRANS includes CASTROL SYNTEC. Thought maybe someone knew why they didn`t use MOBIL 1 as in the CORVETTE.
  • guitarzanguitarzan OhioMember Posts: 848
    Both are good. I use Mobil1, and brother-in-law is a stickler for Castrol. He claims Mobil1 turns dark quicker in his Turbo Eclipse.

    Community Leader/Vans Conference
  • sdc2sdc2 Member Posts: 780
    Actually, a dirty air filter filters BETTER than a clean one. The trapped particles narrow the air passages, rendering the filter more efficient. The problem is, that eventually the filter's resistance to flow becomes too great as the passages become more and more clogged.

    I don't think air quality affects suspended contaminants in the oil. I believe most of it comes as a byproduct of combustion.

    Stop-and-go driving is more stressful on an engine than cruising on a highway. Maintaining a constant speed uses a small fraction of an engines power, while accelerating from a stop uses the majority of your engines power. This is aggrevated by the lack of air movement for cooling in stop-and-go, increasing heat stress on the engine.
  • rs_pettyrs_petty Member Posts: 423
    K&N would have you believe that a dirty filter is better, but if you look at their charts a conventional filter is pretty much efficient when new. Even if I believed the "dirty filter theory", which I don't, the tradeoff is being able to get enough airflow.

    Combustion by itself does not create contaminants. The contaminates come from the organic compounds of the fuel or dirt in the air (which is why you filter air before combustion. If what you say is true then why filter the air?). I can't do anything about organic compounds, but keeping as clean an airflow as possible will reduce contaminates, thus keeping your oil cleaner.

    A properly maintained cooling system will keep an engine within designed limits of heat stress. My question is why is it more stressful for an engine to go from idle to 3000 rpm to idle for an hour or hold 2200 rpm for a 1 hour trip. Both are within the design parameters of the engine, both cause the engine to "work" for the same length of time, so wear should not be different. Power, in the terms that I know of, is not a measurement of engine wear. Again, I am looking for a more scientific reason that stop/go driving is harder on your engine.
  • sdc2sdc2 Member Posts: 780
    The "dirty filter" thing is a known fact. I have no connection to K&N, and haven't seen their info, but I do work in the environmental field, which sometimes requires the use of respiratory protection. We often use HEPA filters (High Efficiency Particulate Air) for contaminants such as asbestos, and in the training the issue of filtration efficiency versus pressure drop is always discussed. It is time to change your filter cartridges when it becomes too difficult to breath due to clogged filter media.

    This is analogous to an engine, which also "breaths". The main danger in a severely dirty filter is that the pressure drop becomes too great due to clogging of the filter, and the filter actually ruptures and dumps its full load of accumulated crap into the engine. Also, a clogged filter, though very efficient at filtering, is actually robbing the engine of its ability to breath, thus hurting power and fuel economy.

    Regarding suspended contaminant sources, I was referring to properly filtered air. Of course filtering is necessary, no one wants abrasive particles dumped into their engine. I just think (opinion, not fact) that for most of us, the quality of air we are driving in doesn't significantly affect the quantity of suspended contaminants in our oil. Of course, driving in a dust storm or something is a different story. After all, a certain percentage of particles below a certain size will get through ANY filter.

    Regarding stop-and-go vs. cruising, I thought I did explain that issue, but I'll try again, with some numbers thrown in. Cruising at highway speeds uses only something like 15 or 20 horsepower (this goes higher the faster you go due primarily to wind drag). Accelerating from a stop uses a good deal more, depending on how fast you are accelerating and how big your engine is relative to the weight of your vehicle. The higher the output, the greater stress on the engine. And even though the cruising output occurs over a longer time period than the acceleration peaks of stop-and-go, the low stress of cruising is easy on the engine. That is why you will see people advertise used vehicles as having "all highway miles" or the like, meaning that the actual wear and tear on the vehicle is lower than the odometer reading indicates.

    In other words, the wear on an engine does not increase arithmetically with stress (such as where X work for Y time = 2X for 0.5Y), but geometrically (such as X for Y = 2X for 0.25Y). The formulas are examples only, and not from actual conditions.

    This is all tied into the scientific principle of INERTIA. Remember, an object in motion tends to stay in motion; an object at rest tends to stay at rest. Stop-and-go is working against inertia, and cruising is working with inertia.

    Well, I've rambled on too long already. Hope I havn't muddied the waters too much.

  • rs_pettyrs_petty Member Posts: 423
    In conventional filters there is no medium (oil) to hold the dirt as in the K&N. I agree that as a filter gets dirty it will flow less air (or IMHO, create enough force to pull the dirt through the filter). The tradeoff is effective filtering versus airflow. My original point was the fact that when talking about changing oil every 3000 miles we neglect to include the discussion of when to change air filters. We'll leave the efficiency of a dirty or clean filter to another debate, but I don't see the logic of 3k oil changes and 15k air filter changes. To me its like changing your oil, but not your filter. Oil changes have been touted as the long life procedure by many users and commercial companies. By itself, it doesn't pass the common sense test, unless you maintain the rest of the system.

    Now for engine wear. Let's separate engine wear from vehicle wear. I won't argue that stop/go driving is harder on the vehicle. Brakes, transmissions, u-joints all take a beating in changing the inertia of the vehicle. My point is that for the engine and engine alone it is a mute point whether you are doing stop/go or highway driving. Most wear in an engine is going to be the piston rings or in the valve train. These parts wear based on cycles, not necessarily load or stress. An engine is not stressed if operated within the design parameters. I'd say driving style plays a bigger part in stress than whether it is highway or stop/go. A gentle application of throttle in town is much less stressful to an engine than hammering it into passing gear on the highway because stress would be measured as a function of the change in reciprocating mass velocity over time. I can come up with all kinds of scenarios where highway driving is much worse on your engine than city driving.

    My point is to debunk the myth that oil changes alone will keep your engine running a long time. You must look at the total system and regular changes of all filters (including fuel) and lubricants offers the best opportunity for longevity of the total vehicle.
  • sdc2sdc2 Member Posts: 780
    I agree that driving style plays a big part in vehicle wear and longevity. Jackie Stewart once said that a good driver is a smooth driver. I have always attempted to emulate that ideal, with some success. On my previous vehicle, I went 142,000 miles before my first brake job. And a good deal of those miles were in town. I am not in the slow lane either; I would say I usually drive in the top 20 percentile for speed!

    Anyway, I have to disagree that engine wear is base primarily on cycles. If that were true, everybody would drive around in the highest gear possible all of the time. Any mechanic will tell you that is the worst thing you can do to an engine.

    Compare an engine under no load, turning 2000 rpm versus the same type of engine at 2000 rpm under heavy load using all of its available horsepower. Will there be a difference in wear? Yes. Will the difference be significant? Impossible to tell, there are too many other variables. On average, however, the loaded engine will definitely wear out first.

    Regarding air filter (and other fluid) changes, I think it is important to change regularly. I change my air filter a couple of times a year, certainly more often than every 15K miles. Your engine management computer depends on good airflow to maintain proper fuel/air ratios. A clogged filter cheats you out of some hp, and we can't have that!
  • hall2hall2 Member Posts: 40
    My manual says something like 3 months or 5000 miles. I prefer three months because It would take me 6 months to get to 5000 miles and my truck takes 8 qts of oil.
    4 changes per year X 25.50(dealer)=$102.00
    5 years to payoff loan = $510.00
    4 X 50.71(my office mate's oil change from Jiffylube)= $202.84.
    5 years = $1014.20
    Cost is double!!!!!!
    I could change my self but I hate the lubrication part of the oil change.
  • rs_pettyrs_petty Member Posts: 423
    You can't compare two engines at the same rpm with load and no load. Once you add the load, then the engine must compensate. It will either reduce rpm's until the load causes it to quit or additional throttle will be required to maintain the rpm. Maybe the right comparison is an engine at 2000 rpm with no load and an engine at 1500 rpm with a load. I'd say the 2000 rpm engine would wear out first. If after applying the load you increase the rpm back to 2000 then the engines are equal again. Let's take for example an engine used in tractor pulling. At start, the engine may be making 60% of capacity. As the weight transfers forward (load) throttles are opened to increase the rpm (cycles) and thus make more horsepower and torque up to 100% of capacity. Internal engine wear is a function of the increased cycles (rpm)not the load. If you did not increase the rpm then the tractor would stop at the point where the produced power was no longer sufficient to overcome the frictional forces. In normal driving the same occurs. You have to increase the rpm of the engine to overcome whatever load (friction, gravity) the vehicle is faced with. In 2 cars, both driven for 100,000 miles. Car 1 is a highway only car. Car 2 is a city only car. If the average rpm were essentially (I'd say within 500 rpm) the same then my bet would be that engine wear would be essentially the same. Conversely, if you double or triple the average rpm between the two vehicles the higher average would show more wear whether or not it was the city car or the highway car.
  • djbpmlawdjbpmlaw Member Posts: 5
    I've used Mobil 1 in my '89 Celica from the very beginning. Never changed the oil, just topped it off every month and changed filters at 5K. Car runs great and has 202,000 miles on it. Don't know if its related to oil, but I'll continue the practice.
  • ruking1ruking1 Member Posts: 19,826
    Your case and practice presents an interesting dilemma. On the one hand, common practice and most professionals will tell you not to do what you did and do at home. What most argue about is the practice of intervals, not the practice of never changing the oil. So getting 202,000 with topping off synthetic oil and changing filters is no easy feat.
    While synthetic oils have the lowest ash %; (high ash % in conventional oil is the weak link that lets sludge build up) say that this is a sludge problem to the max, that is the bad news. The good news is that there are hot chemical wash systems, such as "bilstein system" that will clean that puppy right up. All I can say is WOW and hmmmm. Best of luck in the future.
  • ruking1ruking1 Member Posts: 19,826
    Using 3k intervals and 6 qts of oil for 202k you should have had 67 oil changes? So if you change the filter each say 7-7.5k you have gone from a consumption rate of 67 oil filters to 26-28 oil filters, and from 402 qts of oil to app 34 qts. (Should be 26-28 qts but counting a baseline fill of 6 synthetic qts.)
  • shekharpatelshekharpatel Member Posts: 27
    This goes against all the principles of Physics, Chemistry and air filteration. I hope you are not practicing this on your House-air filters, and airpurifiers and such!
  • SPYDER98SPYDER98 Member Posts: 239
    Wow, great, I can't wait to go to Wal-mart today and pick up my brand new dirty air filter.
  • sdc2sdc2 Member Posts: 780
    Yes, dirty air filters are BETTER in terms of efficiency of filtration! They will allow fewer and smaller particles through. However, dirty filters are WORSE at allowing air flow through, due to clogging. The main reason to change an air filter is to maintain proper air flow for the engine fuel/air ratio, not to filter "better".
  • SPYDER98SPYDER98 Member Posts: 239
    What's the point of having a dirty air filter for then?
  • sdc2sdc2 Member Posts: 780
    I don't understand your question...please restate
  • SPYDER98SPYDER98 Member Posts: 239
    What I meant was, for what type of application would you use a dirty air filter, with better filtration, but less airflow?
    As opposed to a new filter with better airflow, but less filtration?
  • jbadamsjbadams Member Posts: 63
    I think air filters are constructed so that they stop particles of a certain size (very small). I don't believe that dirty filters clean any better than a new one does, it just restricts air.

    The K&N filter probably does get better when it gets dirty, because I don't think it stops particles as small as a paper filter does, UNTIL it gets real dirty. That is the magic of the K&N filter, it has higher air flow because it does not stop the very tiny particles, they pass through along with the air. As the bigger particles pile up in the oil soaked fibers, they start trapping the smaller particles, hence, start working better.
  • sdc2sdc2 Member Posts: 780
    A paper filter relies on pore size to filter. When a particle gets caught in a pore because it is too large to get through, it partially blocks the pore and effectively makes the pore smaller, which means that even smaller particles will not be able to get through. That is why a "dirty" paper filter filters "better", but at the cost of restricted airflow.

    A K&N filter uses a different principle to achieve its filtration. The pores are larger, but are much longer and are convoluted to force the air through twists and turns, and also are sticky from the oil. As the airstream travelling through a pore turns, the inertia of particles carries them to the sidewall of the passage, where they impact in the oil, which traps them. This does not result in restricted airflow, at least for a much longer time, due to the larger pore size.
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