2002 Chevy Prizm rated 40mpg. Why am I only getting 32 mpg on highway?

anon70anon70 Member Posts: 82
edited March 2014 in Chevrolet
I bought a new 2002 Chevy Prizm. it has 700 miles on it. on the sticker, it say 40mpg on highway.

i've filled 3 tanks, and i'm only getting 32 mpg. this is 95% highway, no A/C, windows up, tire air pressure at factory recommendations, etc.

So how come i'm getting 20% less than what factory says i should be getting? And how to fix it???



  • opera_house_wkopera_house_wk Member Posts: 326
    is barely enough to get an accurate mileage reading, you're not driving all highway, and the engine isn't even broken in yet. This sounds just about right. If you are doing a lot of highway, the engine is not being broken in properly by driving at consistent highway speeds.
  • lancerfixerlancerfixer Member Posts: 1,284
    Are you using gas with additives, like ethanol? I've noticed a 4-5 mpg drop in my Honda when I use it. Give your engine a little time to break in, as well, before getting bent out of shape about the mpg.
  • britton2britton2 Member Posts: 305
    I have a '01 Corolla - auto with 4 speed - get about 40 MPG on the road and between 30-32 MPG in the city - how are you figuring your mileage? What octane gas are you using? The previous poster(s) are right - your mileage will improve as the engine breaks in -the reason I mentioned the octane is because I get better mileage using 89 versus 87 octane -
  • zr2randozr2rando Member Posts: 391
    I've had engines that improved on fuel mileage for the first 10,000 miles, so relax, give it some time.
    I have always noticed my best mileage is on 87 octane gas, use the lowest octane gas that does not knock, you throw money away otherwise.
  • jgmilbergjgmilberg Member Posts: 872
    When my wife's truck finally broke in we both noticed it. We went nearly 40% farther on a tank of gas than usual, so just give it time. I didn't really figure it out for a while either, I thought the gauge had gotten stuck or something, it was amazing, for some reason all at once in the middle of a trip to our cabin it just settled down sealed up and stopped sucking gas, now it just sips it. Another thing with mileage ratings is that they are done with one skinny 95 pound person behind the wheel with no cargo at all. You might not ever get 40 MPG, but you should be close, unless you are hauling the family for a trip to the beach or doing a lot of car pooling.
  • kkollwitzkkollwitz Member Posts: 274
    From the EPA website: (http://www.fueleconomy.gov/feg/info.shtml)
    "The test simulates a 10-mile trip and averages 48 mph. The maximum speed is 60 mph. The test is run with the engine warmed up and has little idling time and no stops (except at the end of the test)."
    If your driving isn't like this, you can expect different numbers even after your car is broken in. If your highway speed is like mine (75-80 mph), then getting 80% of the EPA may be reasonable.
    It's also been my experience that as highway speed increases smaller/ higher RPM engine mpg drops more than bigger/ low RPM engine mpg does.
    Finally, previous posts are correct, mpg will probably improve over the next 10k miles at least.
    As an example, my recently-sold 1989 Firebird Formula 5.0 improved its mpg incrementally over the years, and was getting best-ever mileage this year.
  • zueslewiszueslewis Member Posts: 2,353
    as mentioned by others. When I was a service manager, I rec'd several notices from major fuel companies to expect a 10-20% drop in fuel economy in the name of saving our environment.

    It still isn't broken in, though, and won't get its best mileage for a while - I can't tell you the number of times I've had that argument with service customers.
  • dudleyrdudleyr Member Posts: 3,469
    I always get much better than EPA ratings on the highway. Remember that they subtract 22% from the actual test number to get the number that is posted on the car - this is to make up for real world people not matching the conditions they use.

    Remember also that some cars with man trans are not in top gear at some of the speeds they drive at for the highway test - all cars with auto trans are in high gear. This is why the tests are biased towards automatics, and manuals can usually do better than EPA numbers while automatics have a harder time.

    My Integra is EPA rated at 24/28. My highway mileage is always over 30 (if I drive 80-85) and is as high as 40 if I stay at 60 mph.

    You might want to add more tire pressure that will help. Car makers usually reccommend too litte - just ask Ford Explorer owners. Call any tire shop and they will tell you to use at least 32 psi all around (sometimes 35) tires will last longer, be safer, and handle better as well as get better mileage. This is at the expense of some ride quality, and vibration isolation. Also always check tire pressure when the tires are cold.
  • dudleyrdudleyr Member Posts: 3,469
    Ethanol has 1/2 the energy of gasoline. Therefore if you use 10% ethenol your mileage drops by 5%.

    Oxegenated fuel is also bad for mileage.
  • andre1969andre1969 Member Posts: 24,880
    ...I've heard the same thing, that engines will often get better fuel economy once they're broken in. That never happened wtih my '00 Intrepid, though. It's EPA rated at 20/29, and that's what it gets consistently. The only time I've gotten below 20 was in the winter, delivering pizzas in bad weather, running on oxygenated gas. And even then, it was something like 19.5, so I wasn't TOO far below the estimate! Best I've ever gotten was about 32, on a trip from DC to Carlisle PA, doing the speed limit, with 3 people on board. I'm at 65,000 miles now, so it's about as "broken in" as it's gonna get!

    As for the Prizm in question, I'd guess it's a manual shift? That's the only model I could find EPA-rated at 40 (41, actually) on the highway. The automatic models are only rated around 33 mpg. One thing about a car with a small engine that has to rev to get its power though, is that it's going to have to rely more on the lower gears for acceleration. For instance, my Intrepid will loaf along at about 2000 rpm at 60 mph, 2500 rpm at 75, and 3000 rpm at 90. However, when you need passing power, it downshifts, and those numbers will jump to about 3000, 3750, and 4500 rpm, respectively (overdrive is about 0.67:1, direct drive is 1.00:1) With a bigger engine, you can often accelerate without downshifting, so mileage won't suffer as much in "spirited" driving.
  • petrnycpetrnyc Member Posts: 47
  • swschradswschrad Member Posts: 2,171
    EPA tests new cars, inside, on a dyno, occasionally. this is not anybody's normal driving mode. it gets worse if you mash the accelerator, drive over 55 mph, drive in wind, rain or snow, with any load in the vehicle, and so on.

    the EPA estimate is not expected to be within 85% or so of a typical driver's mileage.

    if you WERE doing better, and the mileage either suddenly or gradually goes beyond 80% of estimate, time to evaluate whether you are driving or loaded differently... or if it's maintenance time. if you usually got 37 mpg and one Tuesday, you calculated after a recent fill-up and were down to 28 mpg, time to see the shop.
  • v946916v946916 Member Posts: 4
  • v946916v946916 Member Posts: 4
    I own a 98 Prism, owned since new, its a 3 speed automatic rated at 28/32. I have 60K miles and can get 40 mpg without the a/c on. The worst is 30 mpg. At the Under 1K miles I was getting about 30 mpg. I noticed by about 5K the mileage got alot better and first started getting 40MPG then.
    So there is hope !
    I am getting 24 - 27 on my wifes new Mazda MPV. Its rated at 18/24.
  • anon70anon70 Member Posts: 82
    The prizm is a 4speed automatic. and yes the sticker says 40mpg highway. i'm using the manufacturer recommended octane (87).

    it's now at 1000 miles (basically another tank of gas), and I'm still at 32mpg at 95% highway.

    How does an engine "break in?"
  • alcanalcan Member Posts: 2,550
    The piston rings seat in and conform to the shape of the cylinder walls.
  • swschradswschrad Member Posts: 2,171
    or at least that's what Ford wants me to believe, I seem to remember that they do "remind" the new owner to continue to take it easy for something like 1500 miles total.
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