Your correct I was assuming that gasoline engines had a higher BSFC then diesel. I have seen them specificaly for the TDI and they are right about 1900-2000, which is where I cruise. I did assume from past knowledge that gas engines were higher like in the 3k range, mabye not so anymore?

I have heard that higher ICE compression ratios are more efficient- perhaps the diesel 22:1 compression ratio helps.

As mentioned in the opening thread, diesels automatically have a respectable 12% advantage. A gallon of diesel has 112% of the btu's in a gallon of gasoline. If we all adjusted our mpg up 12%, that would definitely help to bridge the divide.

1 gallon of gasoline = 124,000 Btu

1 gallon of diesel fuel = 139,000 Btu


Source:
https://www.eia.doe.gov/kids/energyfa...alculator.html

It probably depends on the engine, but imle most are around the 2-3,000rpm range. For instance, minimal BSFC for the TDI from 2-3k rpm is ~200-215g/kwh, but low load (most driving) BSFC is still good in the 230-250g/kwh range. Gassers have the same minimal BSFC (when taking into account the difference in energy density) from ~2-3k rpm of ~230-240g/kwh, but at anything less than full load, the efficiency starts dropping like a rock, and tends to bottom out at something like 500-600g/kwh from 2-3k rpm for most driving.