Can a 4 cylinder car jump start an 8 cylinder car?

Answer 1

the important thing is the battery voltage they must both be the same

as the answer above stated, with some additions ... revving the 4 energy-producing car should be done no matter the cylinders as often the charging system is putting out very little at idle, just enough to keep the car charging/running. If you want the extra voltage boost to help the other vehicle you should rev the engine.

The only other thing to keep in mind is if both cars are negative ground. Old Chryslers (don't know if anyone still does this) were positive ground and if my mind remembers properly you can't jump a car with different grounds.