I drove my DCH cvt for a week or so(tank of gas) before checking tire pressure. Found all four less than 32psi. I had originally set them at 35psi. I reset them and can immediately see an increase in mileage. Went to dealer today. He sez that if you leave car for service, ie., oil change, etc they check the tire pressure AND SET IT AT WHAT THE LABEL IN DOOR SAYS...in case of the HCH..30psi. Reason for this? Liability. Say someone has pressure at 50psi and gets work done at dealer. They leave, go down road him a bump etc and the tire blows and they get hurt! Can you say law suit in a NY minute! Not everyone like this, but this is why they set it at factory specs. Dont know about all dealers, but you should check it every time you have it serviced. He claimed my tires would not have been changed on the update only, but the fact is they either leaked or were reset.

 

My dealer always resets the tire pressure.

 

Hi DTDriver:

___3 #’s might produce a change in FE but probably not an amount you can measure or feel? The following might be of interest to you given what Krousdb found in his own Prius II when hypermiling using regular to an extreme tire pressure.

Prius II

62/62 PSI. 98.8 mpg at 77F

44/42 PSI. 97.4 mpg at 82F

35/33 PSI. 96.0 mpg at 86F

___When I go in for an oil change at my local Honda dealership (just $9.37 with my own oil and filter no matter if it’s the Ford, the Acura, the Toyota, or the Honda ), I specify that they not touch the tire pressures. They don’t and I am good for maximum FE afterwards. I believe they will not touch tire pressures if you ask them not too.

___Good Luck

___Wayne R. Gerdes
___Waynegerdes@earthlink.net

 

Wow. That's good stuff, Wayne. And here I was thinking 30# up to 44# would yield a 50% boost in FE or something. Kinda disheartening actually.

 

Does the cost of new tires outweigh the savings of FE. Under or over inflated tires will wear un-evenly (cupping or center wear) i think id rather get a few less MPG than replace a $400 set of tires because i wore them out prematurely. Just my thoughts

 

My real life experience with tire pressure can be seen in my charts.

In May of this year, with my car's lpmg at about 48, I raised my air pressure from 34 to 44 in two increments. My lmpg is now approaching 52. I rarely saw a tank above 52 mpg and now see tanks about 58 as a rule.

The tires on my HCH show no worse for the change. My research has found that replacement tires for the HCH should cost about $60/tire. I am saving (at $2/gallon round number) 1.2 gallons/tank = $2.40, more if prices are higher.

My better tanks are also better year over year, which takes into account the weather.

 

Every car I've owned has had them set to sidewall cold pressure rating and had no problems.
My dealer will automatically set it to door specs,but will gladly set my Dunlops to 51PSI if I request that.

I had the recall done and saw a 5-7MPG decrease in MPG, but then I realized I forgot to specify tire pressure and sure enough all were set to 32.
I pumped them back up and now it's back to normal.

I have a deal with my Honda dealer that I get free tires for as long as I own the car.
At 45,000 miles I have no uneven wear, but I've also kept up with the regular 5K miles maintenance schedule (Rotation every 15K, etc).

I've been going for some long distance tank achievements lately.
For the past week or so it sure seemed like I was being Blogged down some and checked my tire pressure.

Both tires on the Left were down to 48 and both tires on the Right WAY down to 28PSI. (Oops)
I pumped them back up to sidewall max cold and instantly gained around 5MPG.
I'm not doing too bad on this tank. Gone 868 miles and fuel is one bar below half.

 

Going for a 1200 mile tank?

 

so... what is the optimal tire pressure then? One that hugs the line between wearing the tires out to fast (and causing the used tire pollution) and getting the best gas mileage possible?

I'm talking about for the stock bridgestones or whatever they are...

 

In my 97 Civic, as measured over a 1.3 mile section of road 6 times (3 in each direction) the results were:

48mph, 46psi tire pressure: 59.7 mpg
48mph, 35psi tire pressure: 57.6 mpg

Probably around 36-40psi. I used to run high 30's on my Civic and it would still usually wear reasonably evenly across the tread face.