Rob,

I remember reading a recent post of yours which sounded like a nightmare (for the cars and yourself). Something about running dino 50-weight in some of the cars, and 10-30 in others.

Why not put the same thing in all of them, then compare again. Since you sounded like you're a dino-phile, the Delo 10w-30 sounded like the best of the bunch. If not, you can get 5-quart jugs of Valvoline or Mobil 1 synth for $12-15 at Wal-Mart and clean those long-suffering motors out.

Also, what's in your diff and tranny can make a diff. After I changed them to synthetic, my car was just slightly snappier, and also slightly quieter. And--it still makes me grin--it shifts easily when cold. Only gained about 1 mpg, though.

The others have hit on the main points - the B230F is low friction, designed for better mileage. Might lead to more quiet running, too (as long as you don't develop piston slap from the short piston skirts!) Computer controls also improved in that time (the B23 uses the earliest form of knock control, while the later models were a bit more sophisticated.)

The rear end ratio has a lot to do with how a car's acceleration feels. My wife's old '83 B23F w/autobox and 3.73 rear-end felt like it could launch harder than my '83 B23F w/M46 and 3.31 rear.

Computers. Think about the speed of change in the computer industry at that time.

How many miles on each car, and what are the rear end ratios for each of the cars? Both of those could have a lot to do with the gas mileage, performance, and sound that come from the engine. Also, I believe the b230f was a "low friction" design (I'm not sure what that means exactly) which may be why your later cars are quieter.