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Petroleum or Synthetic oil for my pickup truck?



  • I took organic chemistry about 30+ years ago and my professor was a petroleum chemist and synthetic oils were just being developed. One thing we found was that synthetic oils seemed to have better adherence to metal parts than petroleum (paraffin)based oils; as such we thought this was a great property as the metal engine parts would have continuous lubrication. This was supposed to translate into superior wear characteristics. Also we found that the molecular properties of synthetics were better in shear strength meaning they would not break down as readily as petroleum oils. What I am seeing in this topic discussion seems to contradict our old theories. So the basic question is: are synthetics really worth the difference in cost?
  • I have used synthetic in my vehicles for the last 6 years or so. What convince me? I changed from 5w-30 pet. to 5w-50 syn. (Castrol Syntec) and my gas mileage improved 2-3 mpg (in the winter time). Most of that improvement was likely realized at cold startup times since my long trip mileage didn't really increase. The extra gas mileage paid for the increase in oil cost AND then some. So I actually saved money by switching to an oil that cost 3 times as much. Again, the mileage increase was mainly in the wintertime, but that tells me there is a benefit year round on cold enngine startups. Good enough for me.
  • z71billz71bill Posts: 2,000
    Why use 5w50 oil - is your every day driver an Indy race car?
  • Why not use 5w-50? It flows the same as 5w-30 yet protects better. Besides, when I switched to Castrol Syntec years ago, it's the only weight it came in. I was a little curious why they ever came out with the 5w-30. I guess for people that were scared of the 50 number in 5w-50 and didn't realize it flowed just like the 5w-30.
  • z71billz71bill Posts: 2,000
    You should do some research on oil - maybe start with your owners manual. If 5w50 "protects" better than 5w30 why don't all the manufacturers call for its use?

    If I had a high mileage (100,000 +) engine that was using a quart of oil every 1,000 miles I would use ?w50 oil - at that point in the engines life who cares - but for a low mileage engine that is running right, not using oil it would be foolish -IMO. If you do the research you will find that 5w50 oil will give you less mpg than 5w30, and in fact be harder on the engine in terms of wear.

    Not trying to give you a hard time - it's your engine - so do whatever you want. I have read many articles on oil, been to a few classes on lubrication of industrial motors -not that I claim to be an expert -but everything I have learned is opposite to what you are saying.
  • The drivers manual is for the everyday person that is not willing to by synthetic motoroil anyway so why would they put it in there? Besides, even though most manuals say to use only 5w30, the dealerships service departments still buy bulk 10w30 and put it in everything that comes their way. Why? I don't know. Many say "It's all the same" though that obviously is not true.

    I didn't claim to be a lubrication wizard so I am always willing to learn more details. In fact I love them but I have never had a chance to dive more deeply into this subject. No time like the present. I was always led to believe that in the multiviscosity oils, the first number was the "flows like" number and the second was the "protects like" weight. Maybe you can help clear this up then. Obviously a 20w50 flows better than straight 50 and 10w40 and 5w30 flow better than their respective straight weight (40 and 30 respectively).

    So 5w30 and 5w50 do not flow the same? Using that logic, does 10w30 flows better than 5w50? I would think the 5w50 would flow better than 10w30. What about comparing the 0w30 with 5w30. They flow the same since they are both 30 weight or does the 0w flow better than the 5w?

    Maybe the difference is in operating temperature and that is what I'm missing. Is that the key to all this? I believe the 'w' weight is at outside temperature before engine operating temp is reached. Is the second number meaningless until we are at operating temps? Just trying to understand.
    Are you saying that 5w50 flows, once at operating temperature flows not better than 20w50 or straight 50 weight?

    By the way, this is all regarding synthetics, not conventional oils, though I'm sure this applies their, too. All I know is when I switched from 5w30 conventional to the 5w50 synthetic in one of my vehicles years ago, mileage improved significantly in the winter time and a smaller amount in the summer. If I go from 5w50 syn. a 5w30 syn. should my mileage increase again or be about the same? As I said in my previous post, the 5w50 weight was all that was available in Castrol Synten when I decided to try it back then and I guess I never really thought I should switch when the 5w30 came out. I thought the 5w50 would be better. Guess it's not from what you are saying.

    What is it about a 5w50 syn oil that makes it harder on an engine that a 5w30? I realize why a 20w50 would be harder on a day to day engine as would straight 50. It would take way longer for the oil to start freely flowing so less oil protecting the engine until it warms up. But when comparing 5w50 and 5w30, what makes the 5w50 harder on my engine?

    (I may not be able to check back for a couple days as I am going out of town for the holidays but will try. I really am interested to find out exactly how these numbers effect real world daily drivers).
    Thank in advace for any more insight you can provide.

    As I said, I started using 5w-50 when it was the only variety Castrol Syntec.
  • z71billz71bill Posts: 2,000
    You are basicly correct. The 5 in 5w30 means when engine is cold it flows like 5 weight oil. I am old enough to remember when you could buy straight 5 weight oil (also 10, 15, 20, 30 and 40) people up North would use the light weight stuff when the temps were below 0. The second number 30 in 10w30 is the weight of the oil after your engine warms up to normal operating temps. So 5w50 oil starts out like 5 weight and ends up 50 weight. In one class I took an old engineer explained it like this: If you were running down the beach on a very hot day you would have 3 choices. 1. Run up on the hot dry sand, 2. Run in water up to your knees or 3. run in the wet sand right at the waters edge. Which is easier? He compared the hot dry sand to a very light weight oil, the deep water as a very heavy weight oil and the wet sand as the right weight oil. To use his example using 50 weight oil would be like running in deep water. I hate to admit this but this example is the only specific thing I recall from his class.
  • Gotcha.

    So, at operating temperatures, 5w50, 20w50, and 50 all flow/act the same. 10w30, 5w30, and 0w30, and 30 all flow/act the same.

    At startup, 5w30, 5w20, 5w40, 5w50, and 5 all flow the same. 10w30, 10w40, and 10 all flow the same. I guess 0w30 flows like air! Seriously, though, if 0w30 flows the best on startup yet protects like any other 30 weight like 5w30 and 10w30, shouldn't 0w30 be the best whether you are in 40 below, 40 above, or 80 degree weather?

    Even 80 degrees outside is a far cry from normal engine operating temperatures so wouldn't the 0w30 then hold the advantage over all others to get 'oil to the vitals' faster and better? My last oil change I switched to Mobil 1 5w30 and now am wondering if the 0w30 would be a better choice. If both are 30 weight at operating temp but one flows better and quicker at starting temperature (the 0w30), shouldn't everyone (whose engine calls for 30 weight) use that? What do you think?
  • z71billz71bill Posts: 2,000
    Your logic seems correct to me. My 99 Silverado owners manual says to use 0w30 if temp is sub zero. I also noticed in one of your prior posts - that most dealers use 10w30. I have run into this problem with 3 different service departments. They all put in bulk oil systems back when 10w30 was the standard, now they are to cheap to put in an additional tank. I bought a book of 10 oil changes for $75 when my 98 Tahoe was new. They gave me all kinds of crap because I demanded 5w30 per the owners manual. The service manager told me the 1 quart bottles of GM oil in 5w30 cost them $1.50 per quart. 10 changes at 5 quarts each would cost them $75. I am down to my last coupon so looks like I will start to change it myself.
  • markbuckmarkbuck Posts: 1,021
    All engine oils thin when heated.

    A 10W-40 multi-viscosity oil will match a straight 10 weight's oil thickness (viscosity) at one specific cold temp (32F). This same multiviscosity oil will thin out less than a straight 10 weight oil as temperature rises. In fact, the multiviscosity's oil thickness' will be the same as a straight 40 weight oil at one warm temperature (200F).

    What happens above and below these two specific temps is not captured by the _W-__ SAE thickness measureing system. Synthetics almost always work better at both ends of the spectrum (more linear). Conventional oils are likely to thicken more than an equavalent synth oil at temps below the "_W" rating and thin more than than the synth above these temps.

    Additionally, and very important, the additives (called VI improvers) tend to break down with time so the less VI improvers one uses, the better. As the VI improvers break down, the oil reverts more and more to acting like the 5W-xx oil weight.

    The only thing I'm uncertain about is the exact temp used to measure viscosity for the low and high temps (I made up 32F and 200F).

    Hope this helps.
  • It has been explained that oil viscosity changes with the temperature of the oil. The warmer the oil gets, the thinner the oil or the easier it flows. To create multigrade oils, viscosity enhancers are added to the base oil stock. The wider the range of the oil operating temperatures the more viscosity enhancers are needed. Remember that the oil's operating temperatures will always range from the lowest ambient temperature (Truck parked outside at night) to a fully warm engine. (About 200-220 degrees) If you oil's operating temperature is significantly above this range you are probably in some really deep used oats.

    There are several important things to consider when selecting the engine oil. You really need to use what the manufacture requires if you expect to keep your warranty valid. If the oil is too thick at normal operating temperatures your mileage will suffer. If the range of the oil's operating temperatures is wide, (i.e. 5w50) the oil contains more viscosity enchancers than an oil with a narrow range. (i.e. 10w30) There is an exception to the rule. If you regularly drive in an extreme climate it is acceptable to use a thinner oil to insure easy starting. Also the thinner oil provides better lubrication during cold engine start up. The thicker (a.k.a. Heavier) weights of oil are less likely to seep between the cylinder walls and rings and are used in higher mileage engines to compensate for normal wear. The heavier weights of oil flow more easily into the wider gaps around worn bearings. In a new engine it would not surprise me if a heavier oil actually increased bearing wear because the gaps are narrower and more difficult to be lubricated by the thicker oil.

    IMHO, While your vehicle is new it is unadvisable to exceed the vehicle manufacturers requirement for oil weights. If the recommendation is for xW40 oil, I would not use xW50 until the engine actually needed it to stop oil burning.

  • When my 89 GMC S-15 had 9k miles on it I started using Mobil 1 5W30. I also put in a quart of Slick 50 at that time. To date the truck has over 111k miles on it and I go 10k miles between oil changes without adding any oil. Since then I've learned several things. 1) I get the impression that the PTFE in Slick 50 can clog the oil filter and is not recommended by Mobil. 2) Apparently you can use Mobil 1 or any other synthetic right away. I have a new GMC Sierra and I plan on switching to Mobil 1 at 3k miles. I know that there are a lot of choices out there, but Mobil 1 has been recently reformulated and it is everywhere, so I'm sticking with it. But I think I'll pass on the Slick 50
  • Anybody have any comments on the Fram Double Guard oil filters that have PTFE (Slick 50's teflon ingredient)? I used them a couple of times with my 89 GMC, but I have no idea if it had any effect. I'm tempted to use the Mobil 1 filter, but they are expensive and hard to find. OK, I know I shouldn't quibble over a few bucks when I'm trying to maximize the life of a $27.5k truck!
  • z71billz71bill Posts: 2,000
    I have read several places that Fram is the worst oil filter on the market. I just stick with the AC/PF 59. They are only $2.99 at Autozone. I change oil every 3,000 miles (which for me is about every 4 months) - this may be overkill, the oil life monitor goes off between 3,300-3,700 - I figure for the $10.00 it costs to change my oil it is money well spent. I also hate the look of dirty oil on my dipstick.
  • It's amazing how much of an education one can get from this site. I have now determined that a Fram oil filter will never be used on my 2001 Sierra! I'll try finding a Mobil 1 to fit, but barring that, I'll use AC Delco or NAPA.
  • steve234steve234 Posts: 460
    The Fram filter that is considered low quality is the base model. The Double Guard and Tough Guard are better rated. One of the best is the Motorcraft filter.
    Slick 50 is a good product that has taken a lot of hits because of cheap imitators. Slick 50 developed a formula that used teflon as an additive, but chemical bonded. Several companies brought out products with teflon, but did not properly bind it and it separated from the other additives. The effect was like adding sand to the oil. The word got out about this and Slick 50 got branded by association.
    While I have always been a fan of Slick 50, with today's synthethic oils, I do not feel a strong desire to continue using it. STP is another good product that is less used today, because the oils got better.
  • It's my understanding that even the Double Guard and Tough Guard filters have the cardboard end caps and the cheesy plastic valve. No more Frams for me!
  • z71billz71bill Posts: 2,000
    IMO both are a waste if you have an engine that is operating as it should. I have used Slick 50 - it did nothing - no improvement in MPG -did not quiet the lifter noise - who can tell if it did anything to prolong (another worthless product) engine life. STP lost several law suits back in the late 70's early 80's for making claims that it could not prove. It was a marketing supported scam. The racers edge. Good slogan - worthless product. It was just 80 weight oil, packaged in a cute can. Dump a can of this junk in your car in the winter and it does more damage that good.
  • steve234steve234 Posts: 460
    If you are expecting miracles like curing lifter noise from slick 50, then you are bound to be disappointed. These are not miracle cures for bad engines. STP was OK, but the additive packages standard today made it obsolete. Anyone who has used it and works on vehicles can tell you that it was not 80w oil. Slick 50 is like the synthetic oils. It normally will extend the life of the engine that uses it and may get better gas mileage. There are no absolutes because every engine/driver combo is different. With all the additives available, there are good products and bad. Personally, I would never use Marvel Mystery Oil for any reason, along with most of the other crap on the market. I have been privy to some testing done on Slick 50 and found that it was an acceptable cost/benefit a few years ago. If I was staying with dyno oil, I would still add it. I may not continue to use these products, but I also have no desire for a 286 or 68020 based computer. Time and technology moves on.
  • z71billz71bill Posts: 2,000
    It has been 20 years since I put a can of STP in an engine. My memory may be slipping. What I remember was a very thick oil - almost like honey - am I mixed up? What weight would you estimate it to be?
  • I remember when I was young and dumb instead of old and cheap; I added STP to my 67 Mustang. I think it said on the can to pour it into the engine while the motor was running. That fan blew all of that crap all over the engine compartment! It was FUBAR big time. Now that I'm old and cheap, if it don't need it, its not goin'in there.
  • steve234steve234 Posts: 460
    That is about the best discription. It was about that consistancy, but not slick like oil. I always poured it into a hot engine and then idled it for a few minutes. I used to race a 72 Comet and was always looking for more power and reliability. Had all the then current hot mods, dual exhaust with crossover pipe, flex fan, Offy 360 manifold and the first of the electronic ignitions, a Hayes Magnapulse. It took me three sets of plugs before I found out they had failed to include regapping the plugs from .032 to .045 in the instructions.
  • adc100adc100 Posts: 1,521
    You are throwing away good money and possibly harming your vehicle in the process by not having the proper viscosity. Probably also losing milage. Swith to synthetic oils. It's a no brainer. I use Mobil 1
  • wilcoxwilcox Posts: 584
    There's a word we don't see much these days. Are all motor oils high detergent unless the label says otherwise?

    Is Mobile 1 high detergent?
  • amoraamora Posts: 204
    INHO if you plan to turn in/trade-up in 2-5 years go with the Pepboys ProLINE oil/filters, if you
    intend to keep vehicle 10-100 years go with the
    Mobil 1/filters...
  • this discussion (aka: Petroleum or Synthetic... That is the question) has been moved from the Archived Pickups folder to this board. Happy Motoring!

    Pickups Message Board
  • I've used Mobil 1 for 11 years in my 1990 F150. My 2001 F250 requires 5W20. What do I do now.? Do any of the synthetics come in a 5W20?
  • axle59axle59 Posts: 28
    I used to have an '84 civic that got 32mpg. I started using synthetic and my mileage went up to 36mpg. Ever since that time I have used nothing but synthetic oil. I just bought a 2k1 nissan frontier and will be putting synthetic in it after the inital 3k oil change. As for the additives I reccomend using prolong. I had a buddy put it in his sentra and he drove all the way from Barstow to San Diego in the middle of the summer with no oil. Not on purpose he just failed to check his oil before he left. No engine damage at all. One more thing on synthetics. If you are gong to use on I would only use the Mobil 1. I used to use Castrol Syntec but I found out that they changed their formula last summer. They are now using a modified petroleum base instead of a true synthetic base. Mobil took them court over it and the judge upheld Castrol's end stating that a modified base can be called synthetic because it has been altered. Funny thing too is the modified stock only costs about half as much to make but Castrol is still selling it for $4.25 a quart.
  • I have always had good luck with Valvoline. Does anyone know about, or has anyone had any experience with Valvoline's synthetic product? Just curious.
  • I just bought a 2001 F250 Crew 4WD with the V10. They recommend the 5W-20 oil, I can't find Mobil1
    in that viscosity! Auto Zone had no oils AT ALL of that type!!!! HELP! I am sure I can substitute 5W-30 in Mobil1, but am worried my gas mileage will get worse than the 12mpg I now get?
This discussion has been closed.