Question about premium gas...

91 octane is considered premium fuel.

A little bit of info about octane.

The octane rating is the fuel's resistance to spontaneous combustion under compression. The higher the octane rating, the more compression it takes to make the fuel spontaneously ignite.

A high compression engine requires higher octane fuel to prevent detonation. Detonation is a condition where the fuel air mixture ignites while being compressed before the spark plug fires. Detonation can cause serious internal damage to an engine.

Modern computer controlled engines have a knock sensor to detect detonation. When detonation is detected, the engine management computer will adjust the fuel / air mixture and ignition timing to stop the detonation and protect the engine. When this happens, there will be a loss of power and fuel economy.

Your Caddy has a 10.3 to 1 compression ratio. You need to use a higher octane fuel when you go over 10 to 1 compression.

The link below will tell you all about how gasoline works. The 4th page of the article explains octane.

a car built fopr premium runs better on it...that said try 91 see how it runs..