Some of these newer cars require premium fuel. What happens if you use just regular fuel in your new Lexus? What could be damaged? What about you guys with high compression race engines? What happens if you use low octane pump fuel? My mom has a friend who bought a VW and is doing half and half premium and regular. This voids the warranty couldn't it? What could happen? Thanks, I've always wondered.
The lower an octane rating is the lower temp it takes to ignite the fuel. Higher compression causes higher heat in the cylinder. Carbon buildup on the pistons can easily reach low octane ignition points. The higher the compression an engine has the more octane it needs to run correctly. If you use fuel that is too low an octane it can burn at the wrong time in the piston cycle. Instead of igniting the fuel upon full compression it ignites earlier in the compression stroke, resulting in less power. This is real tough on rings and the engine as a whole. You generally get a pinging sound out of the motor when this happens.
A lot of new cars recommend high octane fuel, but that doesn't mean they'll be damaged if people run cheaper stuff in them. Manufacturers know many drivers are cheap or dumb and engineer the car to reduce igniton timing in order to prevent preignition and pinging if lower octane fuel is used. In normal driving the only thing lost is a little power.
