Don

Thanks for that. Yes having once seen it, as happens in life, I have seen more on the subject since. I do believe that Honda are very sincere in what they do and that it is not just marketing hype!

Well, it's been almost 5 tanks since I started this thread. I checked the tire pressure and found it was *under* the recommended pressure of 30 psi! So, I inflated them up my tires to 35 psi and I thought I'd report back...
(note: I inflated them on a cold night after driving 20 miles. The "cold" pressure may have been a bit less..)

Previous to me finally checking the tire pressure I was getting 44.6 mpg on most tanks. After inflating the tires:

1st tank: 46.1
2nd tank: 44.2 (my husband drove for at least 100 miles on that tank-- he has a lead foot!)
3rd tank: 46.1
4th tank: 46.9 (I got to drive in an ideal setting: a nearly flat 40 mph road. Cruising the 101 is fun!)
this tank (half): hovering around 46

Did I change my driving habits? I don't really think so... Or maybe after 50k on the car I've become a better driver or the car has been "broken in" or both. And I do realize that the numbers translate to only about 10-20 more miles per tank. But I'm pleased!

My un-scientific conclusion? Having the tires *at least* properly inflated, and perhaps a bit over makes a difference (small, but noticable) over having them under-inflated.
--A

Amy. Ah yes but what about the ride? Was there any noticeable change in the comfort and quiet?

Nope, I didn't notice any change in the ride.
--A

Just my two cents about my recent finding with tire pressure. Over last two tanks of gas I rasied my air pressure in all four tires to 46 PSI to try and see if it would boost FE. This increase in tire pressure lowered me FE for one reason, there was too much air in the tire and the car was harder to control. It was harder to keep the car in the lane and it seemd to want to float away. Also, March has been a very windy month and the pressure changed with the combined heavy wind seemed to increase my resistance and I had to work twice as hard to achieve lower (3-4) MPG than my average. Since then I have decreased my air pressure to 42 PSI cold and my FE instantly was boosted to previous levels and was much easier to maintain. I hope this helps.

That's my conclusion as well. The claims of +3mpg for maxing out PSI on all 4 corners is just not realistic.

I am tempted to say this "comes up" all the time, but honestly that would imply that it ever stops being discussed. For those really interested in max tire pressures, feel free to read this post:

35psi versus 46psi: A controlled test

The bottom line was that it definitely helps, as I did 6 runs at each tire pressure, very closely controlled and the results were consistant, seemed fully valid, and supported my theory that higher tire pressure (even well above the suggested pressures) still help out. The exact difference was 3.6% at a steady 48 miles per hour. Obviously with accelleration and idling, the average over a whole tank in suburban driving can end up being even lower.

Conversely, if you coast extensively, the difference could be more than 3.6% by going to higher pressures. It's heavily dependant on your driving style. I believe someone else already pointed out the biggest assistance they noticed was extended coasting range. If you use that to your fullest advantage, I wouldn't doubt you could squeak out 3-4% over a whole tank by maxing out your pressures to the number listed on the sidewall. At the same time, you have to decide if you care about potentially sacrificing lane stability (some tires/cars are worse than others for this) and road comfort for the last percent or three.