[101Volts]

Originally Posted by XYZ

With those made before 1990 this is more typical of the MPG realized in typical use: 1988 Chevrolet Caprice Classic Wagon 5.0L V-8 automatic fuel economy analysis (since October 1987 for North America U.S.)

Note that no data is given for speeds below 50 MPH. In city driving in the lower gears actual MPG is more like 12-14 MPG.

That's informative.

And Funkhoss, I do believe the whale wagons (That's the term for GM 1991-1996 full size station wagons) can get 30 MPG Highway or more with gas engines. I got 28+ MPG on a recent (Mostly Highway) trip in a 2000 Dodge Caravan (See fuel log), Which is a comparable car to your wagon according to EPA MPG figures (Though it doesn't have the exact same figures, It's fairly close) and the coefficient of drag which is the same, Stock. Just keep at it with little improvements here and there and eventually, "You got a stew".

How's the tire pressure? You might benefit from seafoaming the car prior to an oil change too, That'll remove carbon build-up and junk in the engine but I wouldn't recommend it if the car burns oil or has an oil leak; I said that just in case because I don't know your car and I do know the miles on your wagon are under 90,000, And it's been recommended to not seafoam cars with over 150,000 miles.