08 Prius MPG woes after new tires

First, make sure that the tires are inflated to 40-42 psi. They are most likely at 32 psi from the shop. Second, all new tires cause an mpg drop for a while, so be assured that there will be a gradual improvement as the tread wears. Many posts about that aspect.

Third, those are not necessarily the best tires for low rolling resistance. Here is the list:
Low Rolling Resistance replacement tires: Current List | PriusChat
Some do much better than others, and in a car like the Prius, that is quite noticeable.

 

No, 40 in the rears. Slightly less in the rear improves handling. The Integrity is OK, just not the favorite here on PC. Give it some time.

 

i would double check the mfd reading with a volt meter on the battery or jump points, after the car has been off for 4 hours or so.

 

sparks are a possibility, but not likely since your change happened with the tyres. they can be done anytime, the manual says 120k i believe. tranny oil is a good idea, but won't effect mpg's.

 

Look into LRR "low rolling resistance" tires. There is a lot of effort put into creating a tire that does not deform as it rolls, which means less energy is wasted in compressing and relaxing the rubber continuously. The trade off is harsh ride, as the tires are also part of the suspension system. The Toyota spec is for a cushy ride. The higher pressure is for better mileage. Anything up to the sidewall pressure limit (usually 44 psi) is fine if the ride is acceptable.

 

All good advice above, but one other point. You say you had an oil change. What oil grade was used? And have you checked the level of oil to make sure it is not over full? As this has a detrimental affect on the Prius.

John Britprius)

 

Low tyre pressures will cause havoc with your MPG.
If you changed the oil yourself you know the oil level, but if a changed by someone else it can be overfull even if the grade is correct.

John Britprius)

 

But....as BritPrius said.....check the oil level yourself. Very quick, simple, easy to do....even I can do it. Just let it sit overnight, or at least three or more hours before you do it. Personally, I never would trust any of those oil change places.....heck....I wouldn't even trust my husband...he would be tipping back an IPA while pouring and would probably put the whole fourth quart into the car.

 

Do check the oil level yourself. Just a little over three quarts is usually what it takes. It's commonly overfilled, even by the pros.

How has the weather been there? Temperature affects fuel economy considerably. If temperatures have been dropping, a decrease in fuel economy is expected.

I found the Integrities to roll pretty nicely, but I would never buy them. I would only run them if they're already on there. I find them to be overpriced and underperforming. They somehow manage to combine low grip, fast wear, high noise, and high cost--I don't know how they do it! There are much better, lower cost tires (such as the awesome Hankook Optimo H727!).

High tire pressure definitely helps tires roll, by reducing the rubber deformation at the contact patch. The manufacturers usually recommend lower pressures due to ride comfort, but there's quite a bit of efficiency to be gained with additional air pressure. I like 44 psi front, 42 psi back.

 

check the oil level, it's q&d.