Exactly my point yes if his tires are 1.5" taller they will weigh more . . . but once they are moving you will see lower rpm for the same speed if you had been using stock tires . . . yes there also will be a lack of "jack rabbit start" proformace . . .

I don't mind driving 55 today, or any day, but now when I get on the "big road" I bump it up to 65-70! As the speed limit is 75, and most people push that a tad, I just smile as they drive by, and say I'm glad I'm not buying thier fuel . . .

Of course when I was on the Autobahn . . .my wife was screaming most of the time for me to slow down (Well, it seemed like all the time!)