why does my 2002 prius with 70,000miles now average just 39mpg?

Jay C

It averaged around 48mpg. Do you think the battery is failing? What should I do while I still have the battery warranty?

Whitesnake

Because hybrids are manifested propaganda...

rockinnnsteady

with the more mileage added, your cars milage slowly drops, thus by 100,000 miles, i wouldnt be surprised that your milage will join ours in the 20s

DE

I asked the same question about my 2006 prius. Toyota inspected me car and while it doesn't get the same awesome gas mileage they had to clean something out (I don't remember what) and it ran better.

Huba

Have you changed the oil to a thicker grade? Are your tires at the right PSI? Is the air cleaner filter new?































The new 2010 model is improved (50 mpg), a bit larger trunk space, more reaer seat leg room, and is going to be $1000 less than the 2008. Might be worth looking at while your trade-in value is still high.

unplugged-Pro-Peace

battery should still be okay.































have you been maintaining it properly? if not, that's your problem.

mrvadeboncoeur

Has your driving pattern or style changed in the last 7+ years? Different driver(s) over that time? Carrying more stuff?















(Some drivers are more lead-footed than others; some drivers coast and drive more efficiently than others. I know that in the 8+ years that I've had my 2001 Prius, I've stopped playing the "video game" of trying to get the best MPG as I did when I got my Prius, but now "just drive it," so my MPG has suffered. Also, I've moved/changed jobs several times in that period... When my husband drives my car, he always gets better MPG than I do. Shorter trips will lower MPG in any car, as will driving mainly over highway speed limits... Extra weight in the car, as well as towing or having a bike rack or luggage box on the car, will all lower fuel economy by having more stuff to move around and by worse aerodynamics.)































How well have you been maintaining your Prius? Been to a dealership lately?















(It's quite common for dealers to "reset" your tire pressure too low after a service, or overfill the oil, or use the wrong grade of oil, all of which will lower your MPG.)































Have you been checking that your tires are inflated to the factory pressures of 35psi front, 33psi rear at minimum?















(Lower pressures will give you lowered MPG. Remember that tire pressures change with the outside air temperature. At this age, you could also have a tire with a slow leak...)































Changed your tires recently? After 70,000 miles I'd assume that you've changed your tires at least once, probably 2-3 times - are you still using the low rolling resistance Bridgestone Potenza RE92 XL tires, or have you switched to some other brand? (most tires in the proper size don't have the correct load rating!) or have been using winter/snow tires? Most other tires will last longer and have better traction, but expect lower MPG and more road noise.































Did you get an alignment when you changed tires? If you've hit a pothole or curb, your alignment may be out, lowering your MPG, making handling a little worse, and prematurely wearing out your tires...)































Has the gasoline in your area recently changed? Did you change stations, or started incorrectly using "premium" fuel?















(The Prius uses regular 87 octane gasoline in the US. Higher octane fuel, besides costing more, actually has less energy content than regular octane so will give you lower MPG. High octane fuel may also give your Prius a check-engine light (engine misfire codes). The octane rating on a gas station's pump is the minimum octane of the fuel dispensed, so some stations may be giving you higher than marked... Also, gasoline in many places is switching over to E10 (10% ethanol, 90% gasoline), to make the fuel cleaner-burning (as a switch away from MTBE which is carcinogenic). E10 has a lower energy content than 100% gasoline, so expect a few MPG lower when using E10.)































Have you checked your climate control settings lately?















(Heat comes from the gasoline engine. Since the engine is very efficient, it often must run just to provide you with "waste" heat. In the 2001-2003 Prius, the AC compressor is belt-driven off of the gasoline engine, so if you have the AC button on (or have the selector set to the front windshield position for defrosting (AC compressor dehumidifies the air blown on the windshield) - easy to forget you've put it there), the engine will come on just to power the AC compressor...)































There is this Classic Prius MPG calculator in the toyota-prius owner's group, that may help you figure out places that you are losing fuel economy: http://groups.yahoo.com/group/toyota-prius/message/6299































Other than MPG, is there anything else different with your car? any unresolved check engine lights, or weird sounds, or odd handling?































Hybrid battery replacements are extremely rare, in or out of warranty. The only symptom on non-accident caused replacements has been a check engine light with the engine running almost constantly, which doesn't sound like your problem. Only a dealer (or someone with the proper Toyota scantool) would be able to diagnose the stored codes to tell you for sure.

Tom M

Main battery failures are very, very rare. If something, anything, goes wrong with this car, it lights up the dash like Christmas and stores a bunch of codes. Your dealer can check the data lists to see if anything looks off but they probably will just tell you it is OK. Check tire pressures, have driving habits changed, have they reformulated the fuel in your area? Many things can affect mileage.