you can use Jet A-1 in aviation diesel engines. Like the Thielert. I assume a diesel's a diesel, so i don't see why you couldn't use jet A-1 (technically) in a car. However it would be very illegal (i think it's custom's and excise that would get you on this one), just as it's illegal to use agricultural diesel in a car. The only difference being a different colourant, oh yeah and agi diesel's about half the price.