I think, it could lead to, for example, very environment friendly and very efficient urban traffic.
But I also think, it required very precise part construction.
Do such things exist? At least in plan?
Extension: Clarification added, waiting for acceptable answer again.
Extension #2: Despite the "common sense", diesel engines aren't so simple. Although there is no spark, there is a part which injects the fuel in exactly the perfect moment into the piston. This happens with around 2000atm pressure. Maybe this would be hard in case of gases.