I get about 26mpg in my 4.6L Supercharged Cougar if I'm careful....and its tipping the scales at over 4,000lbs with me in it. The 4.6L's are generally better on gas than the 5.0L, but only by a couple MPG generally. Driving style has a lot to do with it. Every time you jump on it out of the hole, or whip out and pass a car, you're killing your mileage. The 3.8L's are generally underpowered, so they expel a lot of energy trying to get the car moving from a halt....which in the end often doesn't make them any better on fuel. The split port engines although more powerful, don't make a whole lot more torque down low. Ford was able to increase the amount of air moving through the engine, but as a result additional fuel is need mileage suffers. Although I will say my old clam shell intake 150hp 3.8L Cougar with 3.08 gears got great highway mileage. Went through two head gaskets though.