Dave99SE

Are there any concerns with fuel grade? I always use the highest Octane fuel grade in order to get the most performance and reduce deposits. Howeverm, I read somewhere that with higher grades the fuel burns hotter and can damage engine parts. Its also relatively expensive.

Confused.

Daniel B. Martin

Nissan recommends 91 Anti-Knock Index fuel for the 4Gen Maxima. In many areas fuel is sold with 87, 89, or 93 AKI. I fill with equal amounts of 89 and 93 AKI. That's the economical way to buy 91 AKI.

Combustion residues (deposits) are not a problem with name-brand fuel regardless of AKI rating. However, harmful deposits may result from an engine which is burning oil, coolant, or an over-rich mixture. These deposits are a consequence of engine condition, not fuel grade. They will shorten the life of the Oxygen Sensors and the Catalytic Converter.

Aside from AKI rating, it is good to know what fuel you are buying. Gasoline delivers better mileage than gasohol.

Guest

How do you know you're getting gasoline instead of gasohol, Daniel? I've never really looked on the pump -- is it there?

Hal

Daniel B. Martin

It's supposed to be right on the pump. Some geographic areas in the US are required to use oxygenated fuels to reduce air pollution. The two leading oxygenators are ethanol (alcohol) and Methyl Tertiary-Butyl Ether (MTBE). In recent months MBTE has been discovered to be a serious water pollutant and its use is being phased out. Maine has already banned sale of gasoline with MBTE.