My 1997 Grand Am V6 was much improved with 44psi in the tires. I don't know how it affected my fuel economy (at the time I was a dumb kid driving way too fast), but the tires wore much more evenly and the car handled a lot better.
+1 for inflating the tires. my family has a 02 buick century with the 3.1 and a lesabre with a 3.8. I don't have numbers for the lesabre but the century gained 4 mpg (29-33) like flipping a switch going from 35 to 44 psi and that was at 70 mph. going up to MN my mom got 35 mpg doing about 65-70 with tires like that. car has 93k and zero mods except tire pressure.
1991 Toyota Pickup 22R-E 2.4 I4/5 speed
1990 Toyota Cressida 7M-GE 3.0 I6/5-speed manual
mechanic, carpenter, stagehand, rigger, and know-it-all smartass
"You don't get to judge me for how I fix what you break"