2002 Ford Ranger Edge 3.0L gas mileage problem?

Hi.

"Keep in mind that OVERINFLATION of your tires will actually HURT your gas milage. The reason for this is because it changes the "footprint" of the tire on the road, or the amount of tire you have in contact with the road. Overinflating tires lessens how much tire is on the road and contributes to slip. The more slip you have, the worse milage you will get."

And

"So if you overinflate your tires, especially on the rear of a truck, then you have increased the amount of slip exponentially."

These are your statements that I'm having trouble with. The first statement I believe is false. If you want to say that overinflation (and we still haven't said by how many psi) will cause poor handling or poor tire wear or less effective braking, then fine. But you are saying that it will hurt your gas milage, and I've not seen you produce any evidence that corroborate that statement as fact. As a matter of fact, the first link you sent sorta hurts your argument.

The second statement: While I'm very well versed in how to search the web, I was fairly certain it would be hard to find the same research you were using to cite those exponentially numbers. That's why I asked you for it/them.

Remember, I'm only speaking to the issue of overinflated tires and their effect on milage. You say it has a negative effect, ON MILAGE, I say it doesn't.

Here's just a bit of stuff I found, one of them from you:

"Method: We drove the 55-mile test loop four times at 60 mph — twice with tires at or above proper inflation. Once, we did the test with the tires 5 psi below the pressure recommended by the manufacturer. Since this produced very little difference we enlarged the gap and under inflated the tires by 8 psi. We felt that it was important to make sure the tires were inflated to the recommended level or above." This from the link you sent.

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"Good inflation: Drivers waste millions of gallons of fuel each year due to under-inflated tires. Maintaining optimum tire inflation is one of the best things you can do to increase fuel economy. Inflate your tires to the upper limit of the manufacturer's recommendations."

"Harder tires present less rolling resistance and improve gas mileage; therefore, the Buick Estate Wagon outperformed our expectations based on our regression model, which did not account for tire inflation pressure. In our model Tire Pressure is a lurking variable, variable that seems to help in predicting gas mileage but is not included in the model."

"and keeping tires inflated to the maximum recommended pressure can improve your gas mileage."

Me again.

I think you would be hard pressed to find anyone in an "official" position suggesting that one "overinflate" one's tires past the recommended maximum (due to liability), but they sure do seem to suggest that you keep it as close as possible. But one wonders, considering "Under-inflated tires can lower gas mileage by 0.4 percent for every 1 psi drop in pressure of all four tires. Properly inflated tires are safer and last longer." what every increase in psi (over the recommended max) would bring?

Any way, I'm done with this discussion. Unless you can produce evidence that shows moderately over inflated tires decrease gas milage, we'll just have to agree to disagree.

Have fun with the Head Gasket :)

Don

<snip>

"Donut" wrote

....if under ...overinflation reduces gas mileage because it reduces the footprint of the tire on the road and contributes to slip. The more slip, the worse mileage. If you overinflate your drive tires, especially on the light weight of a truck rear, slip increases exponentially. ______________________________________________

Friction physics illustrates that slippage is independent of the footprint area of the materials (pavement and rubber). That is: F = U x N where F is the frictional force, N is the downward force on the tire and U is the friction coefficient, probably about 0.4 for pavement and rubber. Contact area is not a factor, because as contact area is reduced, the unit pressure (tire force divided by footprint) increases inversely to keep friction constant.

Almost all the energy loss in tires comes not from slippage, but from flexing in the tire as it rolls. The wasted energy appears as heat you can feel by touching the tire instead of as power for the car. The higher the pressure, the higher the mileage. This is true for overinflation pressures as well, so even dangerous overinflation will improve gas mileage, at the risk of early wearout (from distorted treads) or blowout.

Rodan. _________________________________________________

i'm embarrassed to admit (after my previous post and much anguish and hassle) that after driving two (17 gal.) tanks of fuel i'm getting 20.4 mpg, oh, but, and very happy to admit too!!!

b.w.