What kind of gas are you running? Driving at 75 will drastically reduce mpg. My 2.4L auto has averaged 30.6 mpg and I have 76K miles on the car. Gas mileage is dependent on driving technique. When I'm on cruise at 60-65, I get 35-38 mpg according to DIC. I do manual calculations as the DIC in my car reads low.

I did have plugs replaced at 60K as I don't trust 100K spark plug change. I have to say that at 60 K the plugs still looked good.

 

I run mid-grade 89 octane fuel I watched it closely today driving around the city and the DIC was showing 25-26 MPG fastest speed was 40 and I had it in 5th gear as much as I could

 

Simply having it in 5th isn't enough. You have to find that sweet spot where the flywheel and resistance on the trans is as equal as possible so the engine doesn't work very hard. That could be as high as 4000 RPMs depending on the situation.

Cruising at 35mph going 2000 RPM in 5th is worse that doing 35 mph in 3rd at 3600 RPM

 

Easy to lug a motor down at low speeds, even up to 45....I experiment with "I" in town and see a noticable difference(auto). Find that 'no-load' rpm range and you will see better in town milage. If you hit the gas and it groans its too low....if you barley touch the gas and it scoots your there.

 

Well that sounds like 3rd gear to me.... I will try that and see what happens

 

Since it is mostly flat in Florida and I have an auto, I let the car determine when to shift. Just cruising around town at 40 mph, mine is in lock up and I'm running at 1500-1600 rpm.