I thought I would just stick this post here since I was already speculating about my future car (which is now my present car
).
I got the Spyder, this example came with slick tires, coilovers, and roll bar. Amazingly, even with the high rolling resistance slick tires, I got 40mpg going home doing around 55mph at night, and that includes burning up a bunch of fuel idling to stare at the OBDII scanner. The engine idles at a sort of high 770ish rpm, but the fuel flow rate is indicated as 0.17 gph which is quite good.
The scanner indicated 45mpg, but the scanner thinks the car is going a little further distance than it really is, and uncalibrated seems to read a little high, so I'm calling it 40. I have a sort of hard time believing how high that number is (since it would indicate I got maybe like 45mpg without the idling), but I guess it's possible with an efficiency minded driver such as myself. I did engine-on pulse and glide it a bit, but the car doesn't coast well at all thanks to the big sticky tires, and I actually redlined it a few times for fun so definitely not shooting for max mpg. Even if I discount it another 10%, 36 would be amazing for slick tires.
I'm a little disappointed and also happy at the same time. It seems a healthy engine with high compression ratio and low lift cam profile plus a tiny car does quite well to start with, but beating that number is going to be difficult. I thought this was going to take some work because the 5 speed transmission is so short.
Unfortunately having a job means I will probably not get to removing the serpentine belt and measuring stuff for a while. I believe there is some room in there for the bigger water pump pulley, I haven't given up yet.