I've been having to commute with my F150 the past few weeks while my Ex is down, and pissing and moaning about the fuel mileage. I had been wanting to run some seafoam through my upper intake but didn't get around to it until this weekend. I was getting about 14.3mpg highway in my truck for two tanks. I ran a little seafoam through my upper intake then filled up. Got 15.9mpg this tank. Same route, but the 14.3 tanks were to (downhill slightly) and from (uphill slightly), whereas my 15.9 tank was only uphill (not much though, roughly 200 feet net gain over 85 miles). Nice improvement I would say.

This truck is a 1992 F150 4x4, 302/E4OD/3.55 combo with 33x12.50 tires on aluminum wheels. I'm tickled to have reached 15.9. I think I will try synthetic fluids in the tranfer case and rear end next.