Bumper sticker to remind others to check their tire pressure for MPG

I wouldn't bother, unless it's readily available, and no charge. It makes tire air pressure SLIGHTLY more stable. And the absence of oxygen means less propensity to rust, more so with steel rims I guess. But it's very minor difference.

 

I was joking. I stole that from another forum.

 

Tires also oxidize on the inside, but yeah, only worth it if free.

 

Uneven wear@8. Depending on circumstances, excess wear -> necessary replacement of underinflated tires could cost more than excess fuel purchased. Point is that when you 'make them hard' you avoid both costs.

Was a major topic back in early Prius days.