bad gas mileage

You need to take a test drive. Warm up the engine, reset the mileage meter, and take a 30 mile drive somewhere at a reasonable steady speed (55 to 70 mph). Do it on a dry day with clean roads, and note the temperature and any headwinds. Write down the mileage and specifics at the end of the 30 miles.

This will eliminate or reduce many of the variable from the equation. You might want to run the test again with gasoline from a different station, or using premium gas. Your station may have switched to winter gasoline.

Let us know the results.

Tom

 

FYI someone (Patrick Wong?) posted that Toyota warns against using premium gas on the Prius.

 

Yes, I've also posted it a few times. Toyota warns in their tech manual that using higher octane fuel may cause starting problems. They recommend 87 octane.

I think that the winter gas theory could be part of the issue; I see a couple of mpg lower when they switch here in the late fall and then see a jump in the spring when they switch back.

 

Please copy, paste and answer the questions from http://priuschat.com/forums/gen-ii-...-answer-these-questions-esp-if-youre-new.html.

I don't know how long these short drives are, but if they're too short, there's no way you're going to get 45 mpg. As for variance between the trip computer and your calculation, it's expected due to the "guess gauge" and bladder. You'll need to track both these numbers keep track of averages over time.

 

Yes, yes, we all know that the Prius is designed for 87 octane. I am one of the chronic posters pointing out that premium gas is not better, costs more, and may actually reduce mileage.

The reason that the OP may want to try premium gas is if the premium gas is ethanol free. Gasoline with ethanol will cause a mileage hit. It may be that the OP's gas station just started using gasoline with ethanol. Trying some without it may isolate the problem. Often you have to go with premium to get away from alcohol.

Tom

 

Every time my mileage has dropped noticeably it was either:

Cold/Bad weather (driving thru rain takes more energy than dry pavement)

Tire pressure (the tires will lose 3 or 4 psi over a few months normally)

 

We still don't have enough information. Please answer the questions from post 5. Also, doing as qbee42 suggested in post 2 would help too.

Depending on your conditions and drive, 42 mpg "in the winter" may not actually be achievable for you, given the two factors. There are certain things you can do to help improve mileage in cold weather and on short drives such as grille blocking (cheap), engine block heater (not cheap), change of techniques, etc. But, let's start w/information and checking a few things first.

 

I start out on residential streets then drive on a 50mph highway with traffic lights. With the grill blocked and tp at 45psi I got 25mpg for the 1st 5 minutes then 50mpg for the next 5 minutes. The ICE issn't warm until 190F. There is no way in the winter it is at operating temp in 10 minutes. I also use Shell for the kickback.

IMO your situation is close to normal. The dealer may humor you but they aren't going to be able to help you.

If your short trips are also quick then leave the car on & manually lock the door. This will keep the ICE from running just to heat everything up. Your ICE won't start for at least 15 minutes.

 

As an example of how the type of driving can change mileage, tonight I filled up, reset the mileage meter, and drove around town running errands. I drove 9 miles in 27°F weather with several stops, and ended up averaging 30 mpg. In this sort of weather I normally average 44 or 45 mpg driving 25 mile trips. In the summer I will average 56 mpg.

Tom

 

I also have a 2009 touring that is having similiar problems. When I first drove it off the lot at the end of 2008 i could average about 45mpg going 75 on the highway with ac on just driving normally on cruise control. Then during that first winter my average dropped into the high 30's which was normal for the cold and so i waited until the summer of 09 to watch it go back up. however it didn't go back up it dropped even more into the 35's.
On a recent 150 mile highway trip 75 miles there and back i averaged 35.6 mpg at 75 on cruise control, weather outside was 72 not much wind. The oil is at the top dimple not over, the tire pressure is 40 front 38 back. The battery does test a little weak compared to the test they have posted on here. 12.0 no load 11.7 with load and charging was 14.1 or 14.4 cant remember atm.
I am taking it to the dealer today actually just to have them take a look, if they don't find anything which i doubt then my plan is to replace the battery just to see what that does.

 

+14V is just the charging rate, 12V is right on the edge. Try a new battery.

 

The ICE is running longer or more often trying to charge up the weak 12v battery.

 

I have a somewhat different mileage disappointment. I had a brand-new 2008 Prius Pkg 2 that I loved, and got reasonably good mileage (ave. 42 - 45 or more earlier this year), but it was rear-ended and the car totaled in early March 2010.

After the insurance settlement, I found a used 2008 Prius Touring Pkg 5 that was on special at a nearby dealer for about the same price as my settlement out-the-door. Same color, etc. But this replacement Prius, being driving by the same driver, using the same gas, similar temperatures, driving roughly the same routes the same way, has been getting only 36-38 mpg. I've had it back to the dealer several times, they even kept it for two weeks (and gave me a loaner rental to use), and the only thing I can see that they did was put on brand new Michelin energy saver tires (to replace the crappy ones that had been put on it to sell it -- and I have upped the pressure to 42/40psi). They keep telling me it gets great mileage -- but they only test it to 50-60 on the freeways, and I usually drive 70-75 (both cars).

Its only been a couple of weeks since I got it back the last time, without much driving, but it doesn't seem to be much better -- max 42 mpg indicated so far after a tank of just 39 mpg. Anyone know if this kind of decreased MPG (7 to 10 mpg) is reasonable for the different package levels and models? Seems pretty extreme, and frankly if I wanted to get less than 40mpg I would have gotten a regular ICE vehicle, and saved a bunch of money.

Any ideas?

 

I think it would help to answer the questions at http://priuschat.com/forums/gen-ii-...-answer-these-questions-esp-if-youre-new.html.

In CR's testing, they found the Touring model got slightly worse mileage than a non-Touring. See ConsumerReports.org - Most fuel-efficient cars.

 

That 2008 consumer reports listing is a big help. If I have to go back to the dealer I will reference it and give them a copy.

I'll have to pass on the additional questions on the survey for now, getting ready to go out of town for a few days. Been doing most of the suggested items already. But the bottom line for me is that its the same model year vehicle, slightly different model/equipment (Pkg2 vs Pkg5-Touring), same gas used, same general routes and driving style, same air temperatures, even new LRR tires with 42/40psi, but much different MPG than expected.

I wouldn't mind a mile or two less (as suggested by the CR chart), but as I said, 7 to 10 mpg worse is ridiculous. I'll give it another tank or two, then decide if its really enough improved (or at all), then how to proceed. The only other tip in the MPG thread that might be a clue was the person who claimed he had a big improvement from a simple tune-up -- but the selling dealer had indicated that the engine checked out fine, so who knows if he did a re-tune-up or not. I will also check the aux. battery, but that doesn't seem a likely issue.

That's why I'll probably go to my previous local dealer next (who was much more cooperative and knowledgeable), and skip the guys at the selling dealer who really don't seem too competent in any case.

Thanx for the ideas and feedback. I'll check back in when I have more to report.

 

Sounds like things aren't all that bad with the new tires, now that you're getting back to about 40MPG (considering you were only getting 45 before).

Give the new tires a few 1000 miles to break-in and you'll get another 2 or 3 MPG out of it for sure.

 

My 2012 Prius Four, not IV as it is NOT a 2010 and 2010 used uppercase roman numerals, has started doing the same thing, although it is in the summer. Every tank full is getting one mile per gallon less than the previous. I'm thinking about trading it in on some other brand. As I have found in the past, Toyota will do nothing if you complain about lower mpg. They just tell you that it varies.

 

when did this begin? how many tankfuls/mpg dropped since it started? are you keeping up with tyre pressure, oil level and etc.? the problem with getting another brand is the mpg's will be even lower.