Okay so let me see if ive got the theoretical total picture.

1 gal = 36 kwh

Most diesel generators run at 33% efficientcy and depending on their load they draw fuel eg .25 gal at .25 load. So a 12 kwh generator draws 1 gal per hour. A 20 kwh generator with a 12 kwh load would also draw 1 gal per hour though or atleast thats what this implies. Or does it work by you telling it what load to use and then it produces a set amount of kwh? If thats how it works then batteries would be needed to store extra power difference between set load and actual load.

Now it takes 10 hp x 750w or 7.5 kwh to go 50 mph

So now the AC generator to AC capacitors to AC motor setup would lose 25% of its energy and an unknown amount gained back through regenerative breaking.

So 7.5 x 1.25 = 9.375 kwh to go 50 mph

That would be a drain of .79 gal per hour

So 50 miles per .79 gal or 63 miles per gallon at 50 mph

To go 65 mph i would need 18.38 HP

18.38 hp x 750w = 13.785 kwh

So 13.785 kwh x 1.25 = 17.23 kwh at 65 mph

that would be a drain of 1.45 gal per hour;

That would be a drain in excess of what that generator can produce by 5.23 kwh so either get a bigger generator or use batteries. A bigger generator seems to not change a huge amount for the weight - a 10 kwh gen is 500 pounds, while a 20 kwh gen is 700 pounds. so 200# of batteries gets me 16 wh per pound or 3.2 kwh. So, pound for pound it looks like just using a 20 kwh generator gets me more kwh than batteries do. Of course theres the tradeoff of not being able to make it a plug in hybrid.

Anyhow, thats 65 miles per per 1.45 gal or 44.82 miles per gallon at 65 mph.