Gas mileage went way down ??

What temp do you have the a/c on?

I run it on high for a minute and then set it to 75-76.

What brand/model/size tires? What is the max PSI on the sidewall of the tire?

There is a sticky somewhere titled "why is my mileage low" or something to that affect. Read it.

 

I hope you're not running the AC hard. Short trips and heavy AC use will drop mpg drastically.

Tire rotation can drop mpg slightly if the tires are worn according to specific alignment but that wouldn't cause a large drop and it would be very temporary.

 

Hopefully this thread will help you.

http://priuschat.com/forums/gen-ii-prius-fuel-economy/97814-how-reduce-mpg-loss-because-c-use.html

 

For those who purchased tires from Costco, did the techs filled the tires to your requested tire pressure or they just filled it according to tire manufacture specs?

 

I requested the tire tech. at Costco to
fill all four tires with 44 PSI which is max
sidewall pressure and they did.

They also fill with 44 psi when I have
the tires rotated. With 44 PSI in
each tire afte 61,000 miles they are
wearing evenly, and will obtain
maximum treadlife.

 

Tire pressure makes a big difference. I let mine get low and my MPG dropped significantly. Once I slightly overpressured the tires, it went back up. Maybe not the whole answer for you but likely a part of it.

 

I had a similar problem a little while back when I got my car back from the dealer but it was the 10k service so oil change was involved. To make the story as short as possible. They filled my car w/ 5 quarts of oil(the overfill is even stated on the invoice) which resulted in lower mpg. Also, the tire pressure on the invoice showed that they put it more to their spec but when I checked, it was the same as what I originally had it at. Obviously, I have some doubts in trusting the dealers as they can't seem to do a simple oil change properly.

 

Someone pointed out that they may have done that for liability reasons to protect the dealership. Unfortunately, there doesn't seem to be any way around checking tire pressures when we get the car back from the dealership after service. And oil level.

 

Cindy, its not all tires and air pressure. Your 12 volt battery could be low since you just drive a short distance, the battery may not be charged enough.

 

One thing I have noticed and check several times, If I refill to a full tank, and drive really careful, and get the mpg on CONS to 60+, then drive normally and watch the meter, I can have it hover about 51mpg. I have been stuck in that low 40's range, but that is missleading, you cant get out of that till you resteet the trip settings. When you shut the car off, look at the drive specs for mpg, you will see you got better than the CONS. It is a werid thing on the computer, its calculating, but what, who knows. It is all based on the first few miles where it sets its own metering. You gas it up a hill, you will never get it back to the 50's till it is reset, you will hover in the low 40's or worse. You nurse it to 62, and it will drop to about 52 or better.

 

My mileage went down too on my second fill-up. I can't for the life of me figure out why, unless it's because I decided to try and use ECO mode instead of NORMAL.

Tire pressures are 38psi as they were with the first tank. That one seemed to last and last, but I didn't reset the odometer when I picked up the car so I don't know what the actual mileage was.

Currently the tank is almost half empty and I have gone only 178 miles. I will admit that a lot of these trips have been very short ones with the ICE turning on more often. Of course I realize that uses more fuel but still, I am amazed at how fast this tank is disappearing.

Can using ECO mode really make it drop like I am describing?

When I first got the car I only drove it in NORMAL because I hadn't found this great forum and didn't know any better.

Thanks to all

 

If you only have two tanks under your belt then I wouldn't worry about anything or try to draw any conclusions. You don't even know what your average for your commute should be. Eventually you'll figure out your average for each season, weather conditions, and your driving techniques. Right now you simply cannot say anything about the differences between Eco Mode and Normal Mode. Just drive the car for awhile.

 

I have found, consistently, that tire rotations and tire replacement ALWAYS lower mileage significantly (from 50+ to about 42). The mileage will then creep back to normal, after 1-2k miles. I have some doubts on the value of tire rotations, based on the cost, loss of mileage, and the additional wear on all 4 tires each time you rotate them. The other way, you change 2 tires at a time. The fronts will wear faster than the rears.

 

unless they wear unevenly, then rotating might extend longevity.

 

IMO since the front's do wear faster than the rear, rotating the tires will help to equalize the wear on all four tires and increase longevity of the entire set of tires.

Ron (dorunron)

 

If the tires are wearing uneven, you probably have another problem (struts/alignment/balance/etc.) Doing a rotation won't fix that problem. I do know, however, that many people believe in doing rotations. No big deal.

 

Running ac will def. dropMPG. DO NOT RUN WITH THE MAX PSI IN YOU TIRES. During the sumer months hot temps and hot pavement will increase you PSI in your tires. To much PSI will ruin your tires could cause a blow out. Rotating your tires every 5,000 miles will extend their life and should not affect your MPG. Running the correct recommended Psi in your tires will give you a smother ride and more traction on wet pavement.

 

A person can run whatever PSI they want in the vehicle it is up to them to research what they think is best.