Hello
 

I have camry 2003 toyota!!

I got 18.9 mpg on last fillup, (60% city)
this time the car did 25mpg!! (40%city)

dont understand the 6mpg jump increase!! used fuel from KROGER instead of BP!!
I just increase tire pressure from 30 to 40psi!!

bought car used!!! could it be stale fuel is burnt???? !!

i am anal when it comes to hypermiling!!!

Could be the tank took more or more highway or tire PSI - glad your here !

Tire pressure can have a big impact, and you greatly increased it. Then depending on where you are, you may have put ethanol free gas in.

What would you say is a safe figure increase? I can see the "max psi" on my tyre walls, but it does say "US ONLY", whether thats because the mainly straight roads have little impact on tyre wear, or because saftey regs are stricter here im not sure. But im willing to try a small increase.

There is a safety margin in the max side wall numbers. Some of the more extreme hypermilers exceed it. Unless there is many nasty pot holes in your roads, that should be a fine point to start.