Originally Posted by Evil_inKarlate

I've heard one can potentially save 3% on your gas mileage. If you fill up 3x a month at $50, that's potentially $4.50. however, I've also heard that only about 1 in 10 cars have low enough pressure that they'd save that 3%. Unless you have reason to believe you're one of the 'low pressure offenders', you're basically betting that the 15 cents expected value in savings is worth more than the time you spend checking your air at each fill up.

This is a new idiot light that means something specific that most people can fix themselves. Check Engine can means dozens of things, most of which the average user cannot do anything about, short of scheduling a trip to the shop. So if the light Does come on, I think most people would actually take care of it.

The 3-4% is in the individual instance of having significantly low tires, but since not all, or even quite few, cars fit that description, the across-the-board savings are significantly less.

(All emphasis mine - Ei) I agree - It's funny how often DrG is right about things!

I don't doubt they can be made rather effective, if they aren't already so. But is the extra cost and maintenance (and gasoline used to lug the additional hardware everywhere with your car) worth more than the stastitical $25-$150 saved on gas? Or if one wants to be generous, that plus the less than one in a million chance that yours will be one of the estimated lives saved?