Choose the right octane rating for car

Gas stations offer different octane ratings on their gasoline. Diesel, 87, 89 and 92 octanes are most common at standard American gas stations, but not everybody knows which fuel is right for their car. The owner’s manual helps here, but have you ever wondered why? About.com has some ideas, and here’s a brief summary for your convenience.

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Are you picking the right octane rating?

The octane rating of gasoline is a measure of that gasoline’s resistance to knocking. A knocking sound occurs when your internal-combustion engine’s gasoline-air mix ignites prematurely rather than burning smoothly and efficiently. Isooctane and heptane are the points of reference when a gasoline’s octane rating is established. The former compound has 100 octane, while the latter has no octane rating at all. Untreated gasoline, says About.com, is 70 octane – that’s 70 percent isooctane and 30 percent heptane. Lead used to be added to gasoline to cut back knocking, but now that emissions standards require unleaded gasoline within the U.S., more costly compounds are used to raise the octane rating.

Is higher octane the obvious answer?

Old engines regulated the fuel mix with the carburetor, and they benefitted from higher octane rating gasoline. More advanced engines became common in the mid-1980s, and fuel injectors took over the carburetor role. At that point, the octane rating standard within the U.S. became 87 octane. This enabled efficient function without overwhelming the emissions system.

Is using mid-grade gas any better?

There’s a common misconception within the U.S. concerning standard-, mid- and premium-grade gasoline. Depending upon the state, the matching grade designation for the octane number varies. One state may require a minimum octane rating of 92 for premium, while one more might allow 90. Again, paying attention to the owner’s manual and yellow octane stick is important.

Ready for premium blend?

If your vehicle calls for a higher octane rating, it is because you have a high-performance engine to work with. These engines are ultra-efficient and avoid passing unused fuel into emissions and the catalytic converter, which would produce a distinctive egg-like smell. As an addendum, it should also be noted that some large cities require reformulated gasoline. Clean-burning comes from oxygen infusion with this special formulation. Just don’t drive with too little fuel in the tank; that’s muck up the valves and filters. Running within the muck destroys the fuel injector over time.

Find a lot more data here:

http://chemistry.about.com/od/chemistryarticles/a/which-gasoline-to-buy.htm

http://chemistry.about.com/od/chemistryarticles/a/which-gasoline-to-buy.htm