Higher tire pressure -> lower MPG??

[cyclopathic]

Just switch from Dunlop Enasaves A/S to General RT-43H, and looks like there is 5-10% MPG penalty. There are other factors in play, such as break in, lower ambient temperatures, stations switching to winter gas mix, etc, but subjectively car does not roll as well as it was on LRR Enasaves.

The only thing I found out of order is that RT43s were overinflated to 49psi. (This is 2000lbs car).

General wisdom of ecomodder says higher pressure = to better MPG, but the question I am contemplating, is there such thing as too much? RT43s are non-LRR tire, but they were designed with "Low surface abrasion technology (LSA®)" belts to reduce wear/friction. Would this also mean that at some point higher pressure will change the shape of the contact patch and increase the abrasion?

[digital rules]

It's likely a combination of the new tires, a less rolling resistant tire & the winter fuel blend.

Higher pressures will always result in improved rolling resistance, especially between 30-50 psi.

[cyclopathic]

Originally Posted by digital rules

It's likely a combination of the new tires, a less rolling resistant tire & the winter fuel blend.

Higher pressures will always result in improved rolling resistance, especially between 30-50 psi.

Well this is a 2000lbs car. 50psi would be equivalent of 75psi in 3000lbs car, correct?

I am seeing MPG improvement after dropping pressure down under 40psi

[roosterk0031]

Too many varibles, old bald smooth tires are roll easier than new tires.

[ksa8907]

Double check your brakes for drag

[2000mc]

Originally Posted by cyclopathic

General wisdom of ecomodder says higher pressure = to better MPG, but the question I am contemplating, is there such thing as too much?

Mpgmetro posted the most though test I can think of

http://ecomodder.com/forum/showthrea...tire-2721.html
The tires tested were rated 44psi max sidewall.

I wouldnt say "too much", but a point of diminishing returns.

[deejaaa]

Originally Posted by cyclopathic

Well this is a 2000lbs car. 50psi would be equivalent of 75psi in 3000lbs car, correct?

I am seeing MPG improvement after dropping pressure down under 40psi

since you don't say what you drive or where you live, i say give more info and get a better answer.

[markweatherill]

I just put some Enasaves on my car, from non-LRR tyres, and was surprised at the noticeable increases in rolling distance and mpg.

I reckon it's going from LRR to non-LRR tyres that's the sole cause of the effects you're noticing.

[CapriRacer]

Originally Posted by cyclopathic

...........
General wisdom of ecomodder says higher pressure = to better MPG, but the question I am contemplating, is there such thing as too much? .......

While I don't think anyone disagrees that there is an upper limit (after all, the tire will burst due to excessive pressure!), there have been long and at times acrimonious discussions on how high is too high.

Among the things that come along with excessive inflation pressure is a reduction in traction, groove wander, harsh ride, and uneven wear.

I am of the opinion that tire pressure needs to be referenced to the vehicle spec pressure, not what it says on the sidewall and I think anything over 5 psi is excessive.

Originally Posted by cyclopathic

...........
RT43s are non-LRR tire, but they were designed with "Low surface abrasion technology (LSA®)" belts to reduce wear/friction. Would this also mean that at some point higher pressure will change the shape of the contact patch and increase the abrasion?

Sort of. Increasing inflation pressure changes the shape of the footprint regardless of who makes the tire and what technology they employ.

Originally Posted by cyclopathic

Well this is a 2000lbs car. 50psi would be equivalent of 75psi in 3000lbs car, correct? .....

No that is NOT correct. While the load curve on tires is fairly linear, it is NOT proportional.

[user removed]

Originally Posted by markweatherill

I just put some Enasaves on my car, from non-LRR tyres, and was surprised at the noticeable increases in rolling distance and mpg.

I reckon it's going from LRR to non-LRR tyres that's the sole cause of the effects you're noticing.

Being the one who changed the OP's tires, a job I think I will never do again, I refrained from posting any response.

Marks post hits the nail on the head, my 2015 Mirage is one of the best coasting cars I have ever driven, including a 1st gen Insight on RE 92s.

I can not remember a single instance where it was confirmed that increasing pressure reduces mpg.

Sorry to the OP for overinflating his tires, he observed it and the gauge read 40psi, versus his requested 38. Having a pressure gauge in my glove box, I figured he could reduce the pressure any time, like myself. In the meantime he could drive the car with (what I thought based on the gauge reading) was 40 psi.

he (cyclopathic) even advised me on placement of the tire in relation to the valve stem while I was changing his tires and the last two (after taking his advice) needed no weight and, as far as I know, were riding fine when we drove back to my house.

We made a deal on his Ensaves, which measure exactly as new 8/32nds in all treads at 3300 miles. I have them for when mine wear out, waiting in the garage. 7300 miles on my Mirage since 5/9/15.

regards
mech