Synthetic oil and tranny fluid for better MPG?

The recommended oil for the GenIII is now 0w20 synthetic, so you won't have any trouble using it. As for the trans, the debate rages on for what you should use in it, but sticking with the WS fluid in there now won't hurt your mileage.

 

I always keep the original size tires on my cars, so I can't help you there. Here's some reading for you.
17" Vs 15" gas mileage | PriusChat

 

15s are better for mpg on Prius

 

I do not know why the effect of tire sizes on the Pris would be any different than on other vehicles as to the impact on MPG. In my youth I never ran my cars or trucks stock and in my experience I never had a vehicle that the gas mileage did not suffer when taller or wider tires were installed. As to skinnier tires..I dont know but there will be a trade off....stability....load...???? I leave my cars the way the engineers spec them out. They tend to give longer, trouble free service that way IMHO

RAL

 

F8L, a member here, was suggesting to sub 205/50R17 for the OEM 17" size of 215/45R17. It's a little narrower/taller, works out to have virtually the same OD as 195/65R15. Bridgestone Ecopia EP420 is one option in that size. This'll reduce width, which improve aerodynamics a bit, and change "gearing" slightly. All towards improving mpg.

I might go the route, when the time comes, but for now there's still lot of tread on our OEM Michelin Pilot, in 215/45R17. Our's is Canadian "touring" model, has same rims/tires as US "V".

In winter I swap out our OEM Michelin Pilots for Michelin X-Ice in 195/65R15 (on steel Corolla rims), and the mileage seems to be about the same, fwiw.

With the lower profile 17" I set pressures around 36~38 psi, and with the 15" snows around 42~44. Setting the 17" any higher makes the ride a bit too harsh, and doesn't seem to help much with mileage anyway.

I use Toyota 0W20 motor oil, and their ATF-WS transaxle fluid. I changed the latter once, at the 1 year anniversary, and will do subsequent changes every 2 or 3 years thereon, haven't made up my mind completely on the interval yet. We're quite low mileage.

 

At TireRack's website, say you're tire shopping, input your vehicle, then specify to only show LRR results (along the left side column). The LRR choices are limited in 17". Unfortunately Michelin's Energy Saver A/S for example, isn't available, either in oem 215/45R17 or alternate 205/50R17. Bridgestone Ecopia EP420 is one LRR choice, in both those size, maybe the best.

Also, keep in mind, LRR is not black/white, there are a lot of LRR choices, but still quite a range in just how LRR each is, they're not all going to give the same results. And of course there are other factors, ride quality, noise, traction and so on.

With your mileage, try calculating too. It's a bit of a letdown: Toyota's notorious for sugar-coating the displayed mileage. In my experience between 5~10%.

 

Are you sure you're not thinking about the temporary spare? There's a sticker in the driver's door jamb on ours, saying 33/32/60 for front/rear/spare.

A lot of people go higher, but not too much.

 

If your getting 54 MPG, You are doing really well considering you have 17" tires on it. Even with optimistic readings of 54 MPG. When you fill your gas tank and pencil it out you will be about 50 MPG, thats really good. Great Job!
Enjoy your car.

 

Yep, but your doing great, keep up the good work!

 

That's the max permissible at max load. In the door jamb there's a sticker from Toyo, quite a bit lower. Most find something in between works.