If we wanted to drive nice but basic cars, the 83 Corolla fastback SR5 was a great one. I could easily operate the clutch and the transmission was geared right. I would drive on the highway to another town 55 miles away and hang out with my wife for a few hours and drive back. That tank of gas would be good for 41 MPG. If a few improvements were made, it would get 50 MPG on the highway. Another overdrive gear would have helped. We have to get smaller to get better mileage. An 87 Plymouth Horizon I owned used to get 42 MPG on a 3200 mile trip out in the West. The Eastern leg still got 41. No frills.
Sure, gas only costed about $.28/gal but, wasn’t minimum wage also about a buck per hour in the early '60s. Filling up your car hurt in those days, it often meant breaking a five dollar bill.
Maybe the OP used Super Shell with Platformate, or Shell with TCP, or perhaps D-X gasoline with Boron would yield this great mileage. Of course, Gulf No-Knox gasoline would allow one to advance the timing and get more miles per gallon. Let’s not overlook the motor oil, either. Gulf “Single-G” motor oil was supposed to increase performance which in turn might yield better gasoline mileage. “Single-G” as I remember was a great harness racing horse–could it be that Gulf oil gave him his outstanding performance?
The Chevette was not actually a new car; it was in production in Brazil and Argentina under another name. A young and promising engineer at GM was given the assignment to “Americanize” (my apologies to Latino-Americans) it quickly, at least cost and to keep the weight under 2000 lbs.
He did all that, but of course the car was not up to North American standards. My sister bought one as a second car, carefully nursed it for 8 years, but basically hated it. Tom and Ray don’t like working on this vehicle since everything on the engine (carb, manifolds, etc) is on one side.
If GM had realized that this was supposed to be an import fighter, rather than an imperfect stop gap, the would have put more effort into it.
The driveshafts of all cars in the 60’s turned at engine speed when on the highway. All transmissions of the era had a 1:1 high gear. The final reduction took place in the rear end, which comes after the driveshaft. The disadvantage here is that the driveshaft turns at engine speed in the lower gears too, where in most cars, it turned at a lower speed. Even that isn’t too much of a problem, but the sudden change in drive shaft speed every time you changed gears could be hard on the driveshaft though.
The Tempest wasn’t the only car to use this arraignment. Porsche used it in the 944 and 928. Corvette uses it today.