D6 replaces Dexron II and III.
The fuel mileage will be a full tune up.
fix all leaks, spark plugs, wires, test the coils and battery, fuel filter, oil change,tranny, ect.
Id further it by running seafoam ( Sea Foam ) thru it, Follow the instructions on the can, but use the vacuum brake booster line to suck the stuff into the intake. It works better for some reason, let it stall and sit, there will be a butt-ton of smoke when you restart it, it will run rough but will smooth out in a few minutes.
This will clean the inside of the intake system and combustion chambers, basically it will clean the whole top end. I swear by the stuff since it taking a neglected abused 4.3 v6 that barely ran, to running used but pampered used.
Do a full tune up, add this stuff, get 2 cans just in case. I gotta cook dinner, ill edit this reply in an hour or so.
