Why not ?
1984 Chevette - 1.6L 65hp inline 4, 2000lbs, manual trans. Consumer Guide testers managed "an honest 29 mpg in the city and 39 mpg on the highway." with a cd=0.42
1989 Buick Park Ave -3.8L 165hp V6, 3339lbs, slush box. 19 mpg city - 30mpg highway, with a cd=.40
Lets see.
With a manual trans. fuel injection and a 100 additional horsepower in a car that weighs 1300 lb. less than what the v6 came out of, with nearly a identical coefficient of drag ,it could easily be expected to deliver high mpgs.
A big plus is that nearly all GM products (engines and transmissions ) are interchangeable.
A GM 60 degree V6 is a direct drop in.
The 3.8 however is a 90 degree. It would require a little more work. (exhaust)
This is the way I see it.
1980's Chevette = dirt cheap
1990's GM V6 = cheap
Having a inexpensive classic 1980's eco box that hauls a$$ and gets great mpg
= Priceless
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