I haven't posted on here in quite a while but I have a few questions/observations about fuel economy in my car.
the car: '02 WRX
I just got back from a long road trip where the average gas mileage was about 28-29 mpg doing mostly highways at about 65 or 70 mph occasionally flooring it to pass slow pokes.
this car has an Autometer boost guage. At 60 mph in 5th gear im pulling about 10-12 inches of vacuum. But at the same speed in 4th gear its about 15 in. of vac. There is about 500 rpm difference between them. Now as I under stand it the more vacuum you are pulling the less throttle you are using. And the less throttle you are using the less gas you are using.
So my main question is, is the rpm difference in 5th large enough to offset using more throttle than 4th to get better gas mileage?