Very true about the less BTU per gallon but it's also about combustion efficiency. At cruise, I got more miles per total gallon up to about 30% propane. Total homebrew system with mass flow of the propane controlled by a fuel map with inputs of throttle position and rpm. Very similar to an EFI gasoline computer with throttle body injection but no butterfly.

Noticable but not much power increase. Both engines were NA.

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Ron Schroeder
'85 300 Turbo Diesel 2 tank WVO
'83 300 Turbo Diesel 2 tank WVO
Some former WVO vehicles since ~1980:
'83 Mercedes 240D
'80 Audi 4000D
'83 ISUZU Pup
'70 SAAB 99 with Kubota diesel
'76 Honda Civic with Kubota diesel
'86 Golf
Several diesel generators
All with 2 tank WVO conversion
LI NY