[JRMichler]

My target speed is 54-55 MPH. The nearest 65 MPH speed limit is about 80 miles from where I mostly drive. A typical 70-75 mile trip has about 55 miles with 55 MPH limit, with the rest at speed limits 25 to 45 MPH, and four miles of narrow twisty gravel road. My average mileage on such a trip is about 5% better than MPG at a steady 55 MPH. My kill switch gets a lot of use.

My tires are 2% oversize, so current gearing is 1800 RPM at 55 MPH with a 3.73 rear end ratio. Most summer highway driving is at 6 to 9 PSI MAP, which is why I think a taller rear axle ratio would help.

I've never looked up the lubricant specs. Engine oil is whatever the 10 minute oil change place puts in.

The factory air dam is well above the low points. Underneath is a collection of huge holes, with the transmission cross member a couple inches lower than anything else.

And agree on the BSFC. When I do frontal area / Cd / rolling resistance calculations, I need to use less than 0.40 lbs/hp/hr to get calculated MPG to match real world MPG.

I doubt I'll ever do it all, but I'm sure thinking about it!