So i'm trying to get an "accurate" reading of the tranny fluid level. The manual says to drive 20 miles to get the temperature up to normal temp. But the guy at the dealer said he usually only drive 5 miles or less.

Which one is right?

 

Doubt if it'll matter on the dipstick either way. Just warm it up and check it while the engine is running. I normally cycle it between R and D a few times with my foot on the brake to make sure the fluid's pulled down, then check it in P.