air pressure change, improve MPG?

38 psi in front and 36 psi in the back is a good compromise between MPG and ride comfort. The ride might be a little harsh for your taste at those pressures. You should see no change in tire wear and have no effect on tire warranty.

 

Max load is printed on the tire itself, never exceed that. Watch your tire wear, if it wears at the edges, more pressure, if it wears in the middle, less.

 

Best MPG would be sidewall max. A good compromise most people here seem to like is 40-42 front and 40-38 rear. The MPG gains per added pressure start going down pretty quick at about that point, while the ride gets rougher.

 

i run 42/40 f/r to max out mpg but it's not enough to notice. ride isn't bad, but our roads are pretty good. no idea about warranty, but i don't see how they would know. wear has been fine for up to 40,000 miles.

 

I think it depends on what size tire you run, on my prius c it has the 15" with a taller side profile, I think the car also comes with 17" wheels with a lower profile tire that is also a little wider with the lower profile tire the ride is already more firm, with the higher profile tires I have I run 50 psi and the ride is fine for me. the area I drive in has fairly smooth roads. If you are driving where there are potholes and bumpy hwys the 50 would be to hard. The best psi for your car is likely the max psi it is listed on the sidewall, on most of the tires I have seen it is 44 psi, or 51 psi. remember if you have low profile tires and bumpy roads then max sidewall not the best IMO.

 

I recently found my MPG dropping slightly during my commute, and it was getting harder to get over 60mpg (UK). I also noticed a reluctance of my Gen II to glide effortlessly like it used to. I got curious - but with good reason.

Y'see, since I bought my Prius in June 2013, I hadn't checked the tyre pressures. Not once! I had the vehicle serviced by a Toyota main dealer last year, and naturally expected them to have checked the tyre pressures.

Well, finally, on a whim (after debating whether to spend £5 having the tyres deflated and refilled with Nitrogen - I finally decided "Meh!!"), I went round to a local Petrol Station and spent 50p checking and topping up my tyres myself. Here is what I found.....

The front tyres were at 31 and the rear tyres had 29 in them!!! I was genuinely horrified. I pumped the tyres up to a 40/38 configuration immediately. I had just refuelled and at the time had a rather disturbing 55.4mpg for the 36 miles I had travelled since refuelling. About 12 miles of driving, after I'd pumped up my tyres, I was up to 61.1mpg...!!!

This shows how important higher tyre pressures are for getting good MPG in the Prius. Suddenly, Hyper-mile techniques are resulting in even higher MPG again. As if last night, I was up to 63.3mpg and that's with a lot of spirited driving in the fast lane.


iPad ? HD

 

I run sidewall max.
Not only is fuel economy improved some 5% over 'factory recommended', the wear is much better, and handling is safer as well. Only downside is slightly increased road noise.

 

Depends on the tire, the tire profile, road conditions and your tolerance of rougher ride. I suspect running tires, especially low profile tires, at or near max sidewall pressure is going to put more wear-and-tear on suspension components.

Try raising pressures moderately at first: say midway between Toyota's recommendation and max pressure embossed on the tire sidewall. Then maybe raise it to max sidewall for a tankful, see what difference that makes.

Personally I find max sidewall territory imparts too rough of a ride, with little or no mpg improvement, at least with our 215/45R17's. I settled on roughly 4 pounds over Toyota's recommendation.

 

Wow! I bought a little "toy" cigarette lighter pump that lives in the "secret compartment" in the hatch (on the left side, fold up the cargo mat, and in the very rear corner there should be a little lid that lifts up). Every couple weekends I go out and make sure they're topped up. Also note: converted from 55.4 mpgUK to 46.1 mpgUS and 63.3 mpgUK to 52.7 mpgUS

I second everything SageBrush said. I don't even notice the road noise with my Defenders.