Really bad MPG since winter hit??

[JCL]

racing: thanks for that calculator, it is interesting to play with.

I used the 4.6 vehicle figures (weight, cd, frontal area) at 5 c (my temp today) and pushed my average speed up to 40 mph, slightly higher than my average on my vehicle. The variables were:

Vehicle weight: 2180.9 kg / 4808 lbs
Crr: .012
Cd: .35
A: 2.8 m2 / 30 ft2
Fuel energy density (Wh/US gal.): 32970
Engine efficiency: .20
Drivetrain efficiency: .95
Parasitic overhead (Watts): 800
rho: 1.269 kg/m3

I got 11 hp total, lower than I had estimated. At 75 mph (hard to maintain that over a drive cycle) it was 43 hp.

I don't know if 800 watts is a reasonable figure, but taking it on faith I got 7.63 l/100 km and 8.38 l/100 km with an 800 kw parasitic load, at 40 mph, representing a 9.8% fuel consumption penalty for seat heaters on high. That is about double what I had estimated.