We decided to see what driving on tires underinflated by 25 percent below spec would do to fuel economy.
Right. 8% underinflation -- what people probably wouldn't notice, yields no noticeable change. So, if you drop the pressure from 30 to 22.5, yes, I can imagine some benefit.
Nobody has said you can't let enough air out to make a difference. The question is whether the kinds of variations that happen in large numbers of vehicles, routinely, makes a difference.
I don't need a tire pressure monitor to tell me my tires are 25% underinflated. The car handles noticeably different, and if I happen to look at the tire it is obvious that it is underinflated.
BTW, the last two cars I've had had tire pressure monitors that would pick up a 4 lb difference -- not 25%. I'm not sure where they got that.
There is no indication, BTW, that the relationship is linear. Intuitively, it is doubtful it is. So, a 1-2 lb difference -- which is likely more typical, may make no measureable difference at all.
Nobody is arguing against properly inflated tires. McCain specifically said, "Yes, you should do that, too". But the idea that this is going to replace the oil we can get from OCS drilling is just stupid.
It is important to differentiate reality versus the kind of rhetoric we heard from Obama and really, that is scattered all over the Internet. It appears, just from googling it, to be one of those "rumors" like you chastised me for a couple weeks ago -- everyone is citing the rumor without any real data to back it up. Even the DOE figures are overstated -- as I mentioned, a DOE engineer yesterday was quoted on CNN saying, "maybe" 1%. |
