Maximizing gas mileage

lapurdylapurdy Member Posts: 7
For both thrift and environmental reasons, I want
to squeeze every mile (kilometre) out of every
gallon (litre) of gas. It would be fun and helpful
to exchange tips with like-minded Edmunds-users. To
start off, here are a couple of questions I can't
find answers to.

1. Gas pumps have a label saying they've been
calibrated at a certain temperature. Here in
Canada, that temperature is 15 degrees Celsius.
Does that mean that when the gas is colder than
that, and has therefore contracted, the pump is
counting off more units (litres or gallons) than
we're actually getting? The point of the question
is that I've noticed my gas milage is substantially
worse in cald weather. I know a major reason is
that a cold engine is less efficient. But I wonder
if part of it could be that the gas pump is
overstating the quantity of gas I'm putting into
the car.

2. Is gas consumption always proportional to
engine speed, such that you always consume the
least fuel when your engine is running as slowly as
possible (given a fixed roadspeed)? If so, I
assume I should up-shift as quickly as possible
when accelerating. Is that right?

Any answers or comments would be helpful. And it
would be great to hear from people who have their
own tips for saving gas.


  • garthgarth Member Posts: 66
    1. any change in gas volume due to temperature is so minimal, compared to the change in engine efficiency, that the effect on mileage is probably not measurable. You're correct - the engine just isn't as efficient in cold weather (takes longer to warm up; air is denser; etc.)

    2. there's a "sweet spot" at which your car will get the best mpg. back in the gas crisis days, this was determined to be about 45mph for most cars, which led directly to the hated 55mph national speed limit... in any case, as far as shifting - yes, you will save a bit of gas by shifting earlier, but probably not enough to obsess about it. the best and easiest way to drive efficiently, imho, is to drive *smoothly*; and keep safety in mind (i.e., don't drive 15mph faster/slower than traffic because "it's more efficient at that speed")

    now, what does it say about our pigheaded-SUV-consume-till-we-puke culture that there are only two posts on this topic?
  • rea98drea98d Member Posts: 982
    And we have a whole conference dedicated to Trucks & SUV's!
  • garthgarth Member Posts: 66
    I *NEED* my Expedition to commute to work, alone! Without it, how would I feel superior?
  • btroybtroy Member Posts: 92
    In response to the original post, other things that we all know to do are keeping your car tuned-up and aligned and in good repair. Use good tires that are properly inflated. Unload unnecessary cargo that you've been carrying around for no reason. Don't warm up your car before driving (not necessary on modern cars, just drive gently for the first few minutes). Combine multiple chores into one trip (better yet, start a car pool or take public transit). Take it easy on the accelerator when you drive. And last of all, the next time you buy a car, get one of those new Hybrids that gets 80 mpg.
  • lapurdylapurdy Member Posts: 7
    I've found a site that answers my initial question about the effect of standardizing gas volume to a given temperature:

    In short, the answer seems to be that the volume of gas does decline in cold weather, but the volume of energy you get per dollar spent remains constant. Or something like that.
  • pat455pat455 Member Posts: 603
    I am reposting this from a duplicate topic:

    0 of 1: (hoping) Tue 22 Feb '00 (05:51 PM)

    Bought a pre-owned 96 Subaru LSi, 2.5 engine,
    loaded, suits my needs well, but on first tank I
    tested, I got only 20 mpg mixed city/highway!!!!
    Can't I get better than that on a 4 cyl? Is the
    AWD causing such poor mileage? Is this typical
    mpg for other owners out there? What can I do to
    improve this? I'm tempted to sell the car but
    don't know what else to get. I'm in sales and put
    a lot of miles on each day, so fuel economy is a
    big factor but I need room for supplies, too.

    Anyone have any thoughts for hoping?

    Community Leader/Maintenance & Repair Conference
  • garthgarth Member Posts: 66
    "on the first tank i tested" ...

    there's problem #1. you need better data; use an average for many tanks of gas, which will be much more accurate. i've found that a given tank can vary by as much as 15% (differences in the pumps, how well i top off the tank, etc)

    are you relying on some sort of trip computer on the vehicle? they're usually not terribly accurate.

    do you make jackrabbit starts?

    you're in sales - do you carry a lot of stuff in the vehicle? that weight hurts mileage.
  • lapurdylapurdy Member Posts: 7
    I think you may be surprised if you check the official gas mileage rating for that 2.5 litre engine. It's true that it's just 4 cylinders, but those are big ones. And with all the power doo-dads and (I assume) automatic transmission, it may be that 20 mpg isn't that far off the official rating. And yes, the AWD does reduce fuel efficiency -- not least because of the added weight.
  • markbuckmarkbuck Member Posts: 1,021
    Lot of those early '90's suburu's required premium fuel, too. Check your owner's manual.
  • btroybtroy Member Posts: 92
    My Mom has the small Subaru (Impreza) with the smaller engine (2.2). It gets just 23 in normal driving. It's a heavy car for the size and the biggish engine and AWD don't help. 20 sounds about right.
  • aawdwagonbobaawdwagonbob Member Posts: 8
    ive tried to change my driving habits, and have realized that they werent too bad to begin with because mileage didnt change much...but the biggest help would be to anticipate, that is get off the gas if there is a red light or traffic ahead, and get back on the gas slowly when the light changes.. in a word SMOOTH driving. plenty of air int he tires too
  • rykeronerykerone Member Posts: 7
    When gas CHEAP, I had a heavy foot, very heavy foot. Loved to drive fast, quick take off's. Since gas is pretty expensive, I have slow down, no more jack rabbit starts, and eveerything in moderation. I agreewith anticipating the red lights, not only does it save on gas, but also longer life on brake pads, since oyu are not slamming on your brakes to slow downnnnn.
  • kimberleekayekimberleekaye Member Posts: 3
    Can going into neutral on an automatic while down a hill or just coasting to a stop help save on the gas since the transmission is not pulling the vehicle? I have 96 Pontiac Sunfire GT 4 cyc twin cam and it seems to be using more gas than before. I know that 6 cyc will use more gas but want one for the extra driving power and horses.
  • fritofrito Member Posts: 70
    sí señorita. in the part of town where i grow up we call it <<mexican overdrive>>. my '62 malibu would go for very many miles extra by using the N position on the shift lever.

    su amigo, frito
  • pat84pat84 Member Posts: 817
    If the gasoline tank at the service station is below the frost line, there is most likely a small variation in the actual temperature it is delivered at summer/winter. If the gasoline was colder in the winter, it would be delivered as a more dense liquid and you actually get more than the calibrated amount. I think that the gasoline actually contracts after purchase and you end up with less than you purchased. In the U.S. they "oxygenate" gasoline during the winter months. I'm not sure what it means; but it translates to lower miles per gallon.

    One other item, in some heavier vehicles especially with a lot of options, a 6 cylinder engine may get higher miles per gallon than a 4, at least if the sticker EPA estimates can be believed.
  • kmh3kmh3 Member Posts: 35
    Once upon a time, the splitfire sparkplug ads claimed that a 4% increase in HP and gas mileage could be had merely by installing their plugs. They also claimed (rightly) that lower vehicle emissions would also result too.

    These plugs do not violate new vehicle warranties either.

    The new Bosch platinum plugs claim to be even better and cost even more, the nice thing is you don't have to gap them like the splitfires.

    I used to get about 1 MPG better with fancy plugs, so for me it takes a while for them to pay for themselves. At $4-6 per plug rather than $1 per plug they are a lot more expensive than standard plugs.

    I recently bought some new cars and found that these plugs are not available for them yet. Too bad, the last three cars I had that was the first (and only) thing I did, change the plugs.

    Other things that can help increase gas mileage are drive less leadfoot, keep your tire pressure up (most tires are rated at 35 PSI so keep them there).

    Avoid myths that premium gas is better for cars that the owners manual says wants regular. Just buy a good brand of regular. Higher octane will actually give lower mileage and performance in a regular engine (which makes the engine feel smoother because it has less power). Higher octane is about ping-resistance only. Higher quality gas is about the brand and its formulation, not about octane at all. So which regular you buy can make a big difference.

    Using premium in a regular rated engine also contributes to carbon deposit buildups which then leads to pinging which then requires to you keep putting premium in to counteract the pinging.

    This is a vicious cycle I was caught in for a long time. My wife discovered the cure when she switched to the cheapest gas she could find (not the best solution, a name brand regular is probably better). It took two months for the carbon deposit buildups to flush out, but they did and her car never pinged again.

    Since gasolines are very different in formulation even for same grade (regular, plus, premium) you kind of have to find which one works best for your car.

    In the end though, none of these things are any where near as effective as buying a car that is designed to get good gas mileage to begin with.

    AWD for example contains a lot of extra drive linkage that adds resistance for every revolution of the tires which means lots lower gas mileage. Unless you really drive on snow or mud a lot, I think front-wheel drive will do it for you unless you have to have the ground clearance.

    SUVS and especially 4x4's are notorious for low gas mileage because of the extra drivetrain linkage, their lack of aerodynamics, and extra weight.

    If you want great mileage, then buy a car that is rated for high mileage in both the city and on the highway.

    High highway but low city MPG ratings mean that much more careful driving habits are necessary to get good mileage overall. Usually you see ratings like this on higher performance cars.

    If you are a smaller person consider your basic economy (compact) car like the corolla/sentra/civic/protege and don't get the model with the bigger engine. I hear that some of these models can even hold larger people well.

    Stepping up to full-size cars (camry/accord/626) does not drop too much gas mileage in some brands but loses a lot in others.

    If you can stand it (I couldn't) the echo/focus class cars (subcompact) are the highest gas mileage cars around (that have a low sticker price). Their drawbacks of poor handling, ugly exterior, and vulnerability to crosswinds was enough to steer me away from them though. Honda has a high-mileage civic model that has none of these drawbacks but it comes with a high-sticker price.

    For me, appearance (look and feel), handling, power, gas mileage, and reliability are the key factors in choosing a car. I bought the protege and did get the bigger engine, so I get crummy city mileage (20-23) MPG and pretty decent highway mileage (27-29). I have seen claims of 30-32 MPG with this car but I have never gotten it. If I had stayed with the smaller engine, both numbers are supposed to go up about 3 MPG. That was a hard decision for me but I chose to have more power. 3 MPG means only $3 per week higher cost for me because I do not commute far.

    So I get high power for my city driving and for long trips I don't feel too much pain in my wallet at the pump. Switching to regular after my wife's discovery also helped a lot to control gas costs for me.

    I have friends that own regular Honda Civics (not the special high-mileage high-sticker price model) who are getting much higher mileage out of them than my protege so that might be a really good car for people who need gas high mileage. Honda is a master of this in their Civic lineup, high mileage cars that get pretty decent power.

    For used cars I don't know what you can do except try to find the original EPA ratings for the vehicle.
  • markbuckmarkbuck Member Posts: 1,021
    And putting "new" ones in give you the mileage boost, not the actual design.

    MechEng '83 and weekend racer.
  • karluvverkarluvver Member Posts: 10
    This is a worthless gimick because the smallest gap only will always fire.
  • dhanleydhanley Member Posts: 1,531
    Splitfire got sued for false advertising, and they no longer claim mileage and performance increases. I bet the claim is only for badly out-of-tune cars. It is true that the smallest gap will almost always only fire.

    I typically ( I have tracked this ) get better mileage than my wife when driving the same car. Reason? She brakes more than I do. When I see red lights or a slow car, I back off the gas right away so that I spend a less time braking. So, all that time off the gas coasting up to the obstacle is saved gas, and if the light changes or the slowpoke moves out of the way before I have to brake, I can resume my desired speed at a higher beginning speed, so less fuel is consumed again.

    This may seem funny, but this is not specifically to save gas when i do it. It just seems the right way to drive to me. When I see car 'a' on the highway approach car 'b' until they're 1-2 car lengths apart, then 'a' stomps on the brakes, I think "What an idiot. Can't they tell he was going slower for the last few minutes? They shouldn't have a licence." On the highway, i've nudged 40mpg in my '96 saturn sl2 with automatic tranny, (39 and change) and gotten over 35 in our saab '900 turbo.

  • jamesk9jamesk9 Member Posts: 18
    I recently purchased a 1998 Grand Voyager LE with the 3.3L (201CI) engine with 18,750 miles. Although I have only put one tank of fuel through, the combined city/highway mileage is averaging 24.6 miles per imperial gallon (21 US Gallon). Is that a reasonable mileage? I recently changed the oil to 5W50 syntheic, raised to tire presssure the rated 44PSI, and am considering putting synthetic in the transmission (chrysler's new 9602; replacement for 7176E). I an also considering replacing the paper air filter with a K&N filter. If I have the transmission oil changed, I was also considering putting in the Bisch Platinum +4 plugs (any idea what came standard on this from the factory) with Accel 9.9MM wires.

    I would appreciate any advice on improving the gas mileage.
  • ccotenjccotenj Member Posts: 610
    a small word of caution on raising tire pressures in an already unwieldy vehicle... while raising your tire pressure that high no doubt improves your mileage (how much, i don't know), it also reduces your contact patch in a vehicle that already doesn't exactly compare to a ferrari...


  • jamesk9jamesk9 Member Posts: 18
    A recent mileage test noted 29 Imperial Miles per gallon (25 US). Although I contribute some of that increase to tire pressure increase, the rest (and probably the majority) was due to being aware of the mileage. I appreciate the note on tire pressure. Any comments on the K&N filter or plugs?
  • ccotenjccotenj Member Posts: 610
    not really any comments for mpg, but i do believe that a properly maintained one will probably give you a few more ponies. depending on the application, of course, and i wouldn't expect a real noticeable feel unless combined with re-programmed ems and a freer flowing cat back system.

    plugs. imo, most of the mileage claims are bogus. if you are getting a good clean spark that ensures complete detonation, then "more spark" isn't gonna buy you anything. i believe that there were certain plug makers who were forced to retract statements about increased mileage.

    your one statement about "being aware of mpg" (to paraphrase what you said), probably is the BEST way to increase your mileage. when you are trying to acheive better mileage, you generally don't use the loud pedal as an "on/off" switch, and accelerate smoother and more gently.

    ymmv. good luck.

  • edchenedchen Member Posts: 31
    Which is more fuel efficient?
    Accelerating hard to turn into heavy traffic or
    waiting 30 seconds for a larger interval to accelerate slowly.
    Driving 52mph for 5 miles or
    Driving 45mph for 5 miles and 1 red light for 30 seconds.
  • lapurdylapurdy Member Posts: 7
    Since starting this topic, I've experimented with lots of the techniques discussed. Thanks to all for suggestions.

    Here are a couple of further thoughts of my own. First, some people (not in this topic) say you should never coast downhill (i.e. in neutral), because (1) you lose engine-braking, and so can accelerate too much, and (2) if you need to take evasive action, you have no power. I think those are certainly things to be aware of, but I don't think they mean you should never use that technique. Sometimes there's no risk of going too fast (e.g. on a gentle hill when your speed is moderate to begin with), and little risk of needing to power away from danger. Applying common sense and staying alert, I've been happily coasting down lots of hills for months now.

    Second, speed is the big, big factor in fuel efficiency, to judge by my results. I get a significant difference in fuel consumption between cruising at 80 kh/h (about 48 mph) and cruising at even 100 km/h (62 mph). If I let it go up to 120 km/h, I might as well be throwing money out the car window. But here again, common sense has to play a role. If all the other traffic is moving at 120, I'm not going to go 80 just to save gas. And on a long trip, driving slowly can add huge amounts of time.

    It's good to see that this topic still has some life, and thanks again for all the insights.
  • hprickettxhprickettx Member Posts: 23
    I have a 1987 Integra 5 speed which is rated for 25 city, 30 highway. I can consistently get 30 mpg on the interstate, no matter whether driving 60 mph or 80 mph. So I go 80 (as does most of the traffic).

    When I had a short commute driving back and forth to work at a distance of 18 - 36 miles each way, the first 5 miles of which were on rural roads, and the rest on roads with posted speed limits in the 35 - 45 mph range and stop lights about 1 - 2 miles apart. I was able to get 36 mpg, a 40% increase over the epa city estimate. I was able to accomplish this mostly by observing traffic, and shifting into neutral to coast up to stopped or slowing traffic ahead from 1/4 to 1/2 mile back, coasting with downhill grades, etc. Also helpful was knowing the traffic patterns, i.e. where traffic normally slowed down to turn in to the McDonalds, etc. and choosing a different lane ahead of time. Also explains why I am able to get 90k+ miles out of a set of brake pads :)!
  • marcbmarcb Member Posts: 152
    hi to everyone, just happened on this topic. just like everybody else i too am looking to increase my fuel mileage.

    back in the 2000 mpv van topics, fuel economy was also discussed awhile back. i'm sharing one of the responses there as this person gave good insight in fuel efficiency.
  • kkollwitzkkollwitz Member Posts: 274
    I agree with many of the posts on this thread about maximizing mileage. But in my case, because my car is both transportation and entertainment, I'm not willing to alter my driving style to increase mileage. Instead of adjusting my driving to max out mpg, I plan my life to efficiently use my car. My daily driver is 11.25 years old, with 64k miles, meaning I drive about 5700 miles a year. I try to always combine errands in single,time-and-distance saving, mentally-mapped trips, typically waiting a few days for a number of errands to accumulate. Driving as little as I do, I don't worry about mpg, except as an index of engine health. The way I look at it, it's irrelevant what your mpg is; what matters is how much energy you use.
  • duffekduffek Member Posts: 1
    I have a 1999 Ford Ranger 4x4 that gets 25-27 mpg
    Highway (I kid you not) and about 17 mpg galavanting about town! I believe the combo of 3.0L V-6, 4.10 axle ratio, 4-speed auto trans and the 16 in. wheels (off-road equipped) makes this tremendous mileage possible. Also, I DO NOT carry around excess weight, or blast off from a stop sign to keep up with the other traffic. It's interesting to note that on the subject of speed, when you double your vehicles speed (ie 30mph-60mph) the drag on it is actually FOUR times as great! And getting ANY mass moving or stopped takes a great deal of energy to accomplish.
    One last comment. I DO THE SHIFTING of the trans, even though it's an automatic! It's also only a machine, just like the "stupid" cruise control machine that INSISTS on flooring it on an uphill grade, regardless of fuel efficiency! I am much better at discerning when a particular power plant is working near it's most effective efficiency for any driving condition. That comes from practice, which translates to experienc. Know the limitations of your vehicle and you'll see what I mean!
  • fastdriverfastdriver Member Posts: 2,273
    A long time ago I read somewhere that putting an automatic transmission in neutral to coast down a long hill was bad for the tranny because it made it overheat. Does anyone know if this is really true or is it and old wives tale?


  • alcanalcan Member Posts: 2,550
    It's true.
  • oldharryoldharry Member Posts: 413
    do not have the simple inverse relationship many believe. Air flow around a car is turbulant not an even laminar flow at all speeds. Sometimes a difference of three or four miles per hour slower or FASTER can reduce resistance dramatically by moving a high pressure area from the windshield to the rear glass. Only driving long trips at different speeds will determine what speed is most economical for your car. My '96 Lumina sedan gets 33 MPG at 68 MPH, but only 29 MPG at 55 MPH. (Checked on several 400 mile plus, each way trips per year for four years) In traffic where there is stop and go, staying at a lower speed saves a lot of fuel. When you start your car, it uses some fuel per hour to run without moving the car, as you go faster, it uses more per hour, but less per mile until you get to speeds that you can use your highest gear without straining the engine.
    Truckers complained about the 55 limit because, many diesel trucks get their best milage about 61 MPH steady cruising.

    Wide open throttle wastes fuel almost any time you use it.

  • oldharryoldharry Member Posts: 413
    speed, temporarily (or pemanently) hooking a vacuum gauge to your engine makes it easier. The vacuum will be higher when the engine is not working as hard. Drive a constant speed for a mile or more, note reading, then add a couple miles per hour and maintain again. If you find a speed where vacuum jumps an inch or more above the next lower speed after it settles down from accellerating, you have found a sweet spot.

  • rdsvideordsvideo Member Posts: 1
    For those of you who own V6 Escapes or Mazda tribute what kind of milage are you getting.
  • pat455pat455 Member Posts: 603
    We have some topics in Town Hall discussing the Ford Escape and Mazda Tribute where you are likely to find owners. You can use the Topic Search feature on the left side of the page for Escape or for Tribute to get a list of them. Check the "last post" date to find out which ones are current.

    Community Leader/Maintenance & Repair Conference
  • guitarzanguitarzan OhioMember Posts: 864
    Right oldharry! Highest vacuum at the lowest RPM will provide the answer for the most efficient operating point.
  • d0cd0c Member Posts: 1
    The gas milage "sweet spot" problem, (here in Europe, at least) is now worse than ever as once the manufacturers realised that their cars were being assessed at 56mph (90kph) they programmed the engine managment chips to burn particularly "lean" at that speed, which makes the engine performance notchy, and it is impossible to be able to match the gas mileage that the government calculates because of this. I guess that it is pretty much the same in the US.

  • greg116greg116 Member Posts: 116
    I am looking to buy a new S-10 V-6 4x4 automatic extended cab sportside. Dont give me junk about choosing a truck over a car: I am 6'4" and have spent my driving life behind the wheel of a Durango. I twist my knee getting into anything smaller than a 4x4 pickup. Besides I love skiing and this is a great vehicle for that, plus I LOVE sportsides!

    Let me say that it's such a nice change from people bashing other peoples cars in the other message boards!

    I was wondering: Have any of you heard of the Fuel Saver Plus? It's a little gizmo custom-made for your vehicle that actually heats the fuel in your fuel line so it burns better, reducing emissions, boosting hp, etc etc... The commercial I saw it on promised up to 20% better economy in most engines, as well as more power, longer life and all that good stuff. Only catch: They cost big $$$, like 3-400 bucks, I'm not sure if thats in Canadian or US dollars, but when I get my truck, thats gonna be the second thing that goes into it, the first being a K&N air filter!

    Second, I have an interesting theory: When we started highway cruising our new 98 Durango (which we did a LOT) the fuel economy wasnt that great. Only about a month ago, I drove it from Calgary to Vancouver over the rockies on a two-day trip, and - brace yourself - averages 18.6 MPG. This is with the 5.9 Liter engine and 3.55 rear end. My theory? Bug deflectors, which we added immediately after seeing all the damage from our repeated highway trips, do more than protect your paint. OK, the K&N helped too. I also did a little city driving in there, so I think the highway mileage comes out to 18.6 or .7

    All this information has been great, I'll make it a point to remember all of them when I pick up my S-10!
  • steverstever Guest Posts: 52,454
    The FTC warns you to be wary of any gas-saving claims for automotive devices or oil and gas additives.

    By the way, I've looked at K&N's website and I see no claims there that their air filters affect mileage one way or another.

    Vans and Aftermarket & Accessories Message Boards
  • tronsrtronsr Member Posts: 46
    You can bet your mortgage that this 20% fuel saver is a P.T. Barnum {there's a sucker born every minute}gizmo.Any device that could improve gas mileage that much would be "NATIONALLY" recognized in a flash.Don't you think "Consumers Report,Consumer's Digest or someone would have a MAJOR report on it if it were "true"??????
  • oldharryoldharry Member Posts: 413
    to heat diesel fuel, using a heat exchanger to the coolant. The suppiler bragged of great savings on logging trucks. Farmers around here tried them on tractors, and took them off because of lack of power. The energy in the fuel is related directly to the mass of the fuel. The heater expanded the fuel, in logging trucks this turned out to be an advantage. They mostly went up hill empty, and down hill loaded. The expanded fuel worked the same as turning down the idle speed.

    Another thought:
    My father was a factory service rep for Hudson Motorcars in the fifties. They used Hydramatic transmissions purchased from GM, and he went to trans school in Detroit at GM. At the class someone asked about the XXX MPG carburators that supossedly the oil companies were surpressing. The instructorsaid he didn't know, but would ask. The last day of class the carb man came and told them, that super MPG carbs were possible, but they could not use them and have a reliable engine. If it were possible, he said, "We'd put one on a Cadillac, and noone would buy a Lincoln that got less than half the MPG. The oil companies couldn't pay us enough to surpress it." Now we have Cadillacs and Lincolns getting MPG that economy cars only dreamed of in the fifties and sixties.

This discussion has been closed.