Originally Posted by Ghost-Flame

Okay as promised. I just finished my aforementioned 400 mile trip. 350 of it was hiway at cruising speed 75 to 80 mph. the other 50 were town and country.

I take this trip monthly. I always set the computer to calc the mpg. it has been running 17.5 mpg with low tire pressure. Today, I'm glad to report that I averaged 20.1 with proper pressure. that's 2.6 mpg more. I know this is anticdotal but that's almost 15% higher. if it was 5% higher that would be good 10% would be awesome. It's just air. that's 12.50 per tank if those numbers hold up for city driving as well. I'll be checking my air pressure weekly from now on.