Regular or Premium

[FoDaddy]

Generally speaking engines that recommend 91 octane have higher compression. The higher the octane of the fuel, the more resistant it is to detonate. It takes less effort to detonate 87 octane which is why it’s used on lower compression engines. If you use 87 octane on a car that requires or even recommends 91 octane the 87 octane will detonate too soon, thus negating the benefit of having a high compression engine. Now the computer can compensate somewhat for this by retarding the timing and going to a different spark table strategy, but you will lose power and your engine will not be running at it’s best possible efficency.