The Service Dept

THE SERVICE DEPT

Allan Girdler

CRACKING THE OCTANE CODE

If it weren't for too many helpful people, choosing the correct grade of gasoline wouldn't be a problem.

But it is a problem. Look in the owner's manual and you can see that the factory wants to help. Always use gasoline with an octane rating of 90, the book says, and adds that the octane should be rated under the Research Method.

Well and good. Trouble is. when you get to the service station, the pump has an EPA octane sticker. The sticker doesn't say "Research Method." Instead, there's a mysterious code: “The gasoline delivered bv this pump has an octane rating of 88." the sticker declares, “and we got this rating by using the

r , M + R r~ \ •

formula ^— = EPA s octane rating.

What is all this ? And how does the motorcycle owner use the rating in his manual when the consumer information on the pump is rated by another method? Through simple arithmetic and a know ledge of how this came about, that's how.

First, the history. There are two methods of testing a fuel to measure its octane rating, or knock resistance. One is the Research Method. The other is known as the Motor Method. How they work and whv they're different isn't important here. What does matter is that because there are two methods, when the EPA decided consumers should have octane information, it also decided not to pick either rating system. Instead, it averaged the two and came up with a number used by the EPA and nobody else.

So. The wav out of this is to begin with a basic fact, namely that EPA's formula takes the rating of a given blend of fuel under the Motor Method and the rating under the Research Method, adds the two and divides by two. The next important fact is that the Research Method gives higher numbers than the Motor Method.

What that means is that if you take a given grade of fuel rated at 94 by Research, it will test out at 90 under Motor. Thus, it will average out to 92 under the EPA system.

How does that help the motorcycle owner'? Once you know the system, you can look on the pump and reckon that if it's 92 EPA, it's also 94 under Research, so if your bike is supposed to use at least 90 by Research, a 92 or 90 or even 88 by EPA will work perfectly

well.