Tire Pressure as it Relates to MPG

[Jace 68 912 RSR]

From a Yahoo article: http://finance.yahoo.com/news/how-to-get--2-per-gallon-gas.html

Check the tires
Savings: Up to 12 cents per gallon.

Under- or over-inflated tires change the way the car handles, adding drag and speeding wear. That, in turn, reduces fuel efficiency by about 3%. Look to the driver's side door panel or owner's manual for information on proper inflation levels, Kliesch says. Don't go by the figure stamped on the tire -- that's the maximum it can handle.

I was under the impression that the difference between what the sidewall inflation max is what the tire can handle and the what is listed on the door jam is reflective of the max inflation under max load.

If I am correct and you are operating under normal load conditions, could you inflate the tire to max sidewall inflation?

Or am I wrong?

[Lupin..the..3rd]

The sidewall number is put there by the tire manufacturer. They have no idea what kind of car it's going to be used on, front engine or rear engine, sports car or station wagon, etc.

Use the vehicle manufacturer's recommendations and ignore what's printed on the tire. The car will handle strangely if your pressures are way out of whack. Just because the tire can safely handle 48 psi doesn't mean the car will safely handle 48 psi.

[HoodPin]

IMHO, the rating on the door jamb is number the manufacturer recommends based upon their choice of tire manufacturer, ride quality, expected driving style, desire to achieve CAFE rating, etc. The car doesn't know how the driver plans to use the vehicle, or what alternative tire brands may be purchased.

The rating stamped on the tire is usually the min & max safe pressures that the tire is designed to operate within. But the tire doesn't know the driving style, the weight of the vehicle, etc.

I believe the tire rating is a better guide, although you need to assess based upon actual driving needs. "Roll Over" of the tread's shoulder is what I look at to try and dial in the optimum PSI. Of course driving on the street, vs on the track, vs in the rain, will "optimally" be different pressures.

[JmuRiz]

For my daily drivers I inflate to the fully loaded suggested rating...so if the car is unloaded it's a little high on psi, but doesn't mess with handling much.

[Landjet]

If you were to inflate the tire to the maximum allowed by the tire sidewall when cold, would that still allow for the higher pressures generated from driving? Or is the tire sidewall number the maximum pressure allowed during driving?

[racer]

If you were to inflate the tire to the maximum allowed by the tire sidewall when cold, would that still allow for the higher pressures generated from driving? Or is the tire sidewall number the maximum pressure allowed during driving?

Sidewall posted pressure is the maximum pressure.. doesn't matter if "hot" or "cold" pressure.

Pressures on the door jam or fuel filler are manufactures recommended pressures.

Is this horse dead yet?

[Noah]

I set mine at 75 PSI and get 50 MPG.

[Trak Ratt]

I set mine at 75 PSI and get 50 MPG, while going 100 mph, up the climbing esses.added :)