FWIW, the original 1982 Vanagon Owners Manual has this to say regarding the use of alternate fuels:

"Winter Operation
"If winterized Diesel Fuel No. 1 is not available, mix Diesel Fuel No. 2 with up to 25% Kerosene (or with regular leaded or unleaded gasoline, if Kerosene is not available).
DO NOT USE PREMIUM GASOLINE."

There's no mention of how much damage such alternate fuels might inflict ..

Jeff