re: Tire pressure and mpg for offroad tires.

The lesser of the two provided they are reasonably close.

I think my tires are 35max and the door sticker is 42 max or something like that. Obviously I use the tire rating.

Draw a line of chalk across the tread. Drive straight down the street for 1/2 mile or so. Look at what part wore off. If outside, put more pressure. If middle, less pressure.

Should be around 30psi, but with different tires than stock, you have to do what I said. The door will not be correct, but close. The tires rating is max psi