NIce! FYI, the 66-69 912 specs show engine's fuel consumption inversely related to torque.

Found this old study I did back when my 2000 S had just 30K miles on it (and the original engine). I scare myself sometimes. Now I understand why I had trouble getting dates.

I did this study on a drive from Philly to Atlanta using the OBC for average miles per hour. I guess the lesson is that the car runs best when it runs fast and the OBC overstates MPG. Below is the raw data and a graph.

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1. at higher speeds you are in higher gears and also likely traveling at more constant speeds ont he highway - this will lead to the positive correlation between speed and economy you show
2. if all the travel was highway, top gear, relatively constant speed, i would predict ( and have measured, but not graphed) an inverse correlation --- e.g.: constant travel, top gear 50 mph woudl be higher than same conditions at 80mph, since wind resistance rises geometrically with speed

For the record, in my 5-sp, 2.7 i just got 30.4 mpg at average speed of 74 mph en route from mid-ohio to New Jersey yesterday. pretty much get on route 80, go home.

Grant

A reproduction of the owner's manual has a graph with torque, fuel consumption (and horsepower.) Engine speed is on the horizontal axis. Maximum torque, 97.6 lb/ft @ 3500 rpm, is where the lowest fuel consumption occurs. The shapes of the curves pretty much mirror each other. Fuel consumption is expressed as "be (g/HPh)." Another graph shows that at 3500 rpm in 5th gear the vehicle speed (discounting other factors) is about 67.5 mph. The "be" difference isn't all that much, but when the "national" limit was set at 55, I personally observed getting better mileage somewhere closer to 65 mph in steady highway driving.

That's why I married young, get 'em when they don't know any better. My wife of 25 years learned early on the eye roll when I pull things like you did. Now, it's an eye roll and a whatever.