Of course ........... if you compare US highways to say .......... NZ highways ................... that wont work

 

My best mileage is around 53 or so, almost 30, via Scan Gauge, on level ground. Highway above 73 starts to drop off fast.

 

Pearl are you saying that we will see the most fuel efficiency at 5,000 - 5,500 rpm? I have been trying to keep her in the the 3,500 - 4,000 range for daily driving. Guess I am doing it wrong!

 

No.

If you were to remove all drivetrain drag, aero drag, etc... and were to measure the engine on an engine stand looking for what RPM is the most efficient, it will be at the point of peak torque (even if you aren't demanding 100% torque), which for the Renesis will be in the 5,000-5,500rpm range.

However, when you add in the other factors, 5,500rpm is far too fast, and the aero drag alone will crush the engine efficency difference between ~3,000rpm at 60mph and 5,000rpm at 100mph. (your S2 gearing will have a bit different speeds at those RPMs).

Lower gear to put your RPMs into the 5k range at 60mph isn't really viable either though, since the increased RPMs for the same speed will have increased drivetrain drag that will also overcome the difference.

 

Aero is the big driver.. I can pull my trailer, do 75, and if I am behind a truck, I am getting high 20's. And, that was before the cat fell off.

@OP, lower the front an inch lower than the back, for aero, but that again is only good on highway.