The octane debate.

Old 03-05-2012, 01:52 PM
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Default The octane debate.

#1. High-Octane Gasoline Is Better for Your Engine
The Myth:
Using premium or super-grade gasoline will give you more power and better mileage, and make your engine run smoother. Think about it: paychecks, simultaneous sexual partners, amount of successive fights you've won against crocodiles -- bigger numbers are always better.

The Reality:
With the exception of a small percentage of automobiles that require high-octane fuel, using plus or premium-grade gas won't do anything for your car. High-compression engines like those found in sports cars require high-octane gas, but not for the reason you might think, which is to go from "fun" to "funnest" as fast as possible. It's because those engines like to squeeze the gas and air in a super tight piston-driven bear hug, and the gas can sometimes get too excited and prematurely explode inside the engine (presumably while muttering shameful apologies into its shoulder). When this happens, it causes a phenomenon known as detonation or "knocking." Even though the engine tries to reassure the gas that it's perfectly natural and isn't anything to be ashamed of, it still wouldn't mind if the gasoline got a little help with its "staying power," which comes in the form of higher octane ratings.
Wait, what were we talking about again?
The vast majority of cars, however, use lower compression engines, so knocking isn't an issue with regular gas. Using higher grades won't make your engine run smoother, won't give you more power, won't improve your gas mileage and sure as hell won't make everybody in high school who makes fun of your hand-me-down Geo Metro sorry. The octane rating is purely a measure of how well the gas will resist knocking and has nothing to do with energy content.
In fact, as many gas stations now add 10 percent ethanol to their gas (pure ethanol sports a beastly octane rating of 113, but actually has 34 percent less energy than gasoline), the overall octane rating is usually two or three points higher than what the label says anyway; i.e., 87 gas is actually closer to 90 with 10 percent ethanol added. That means that even if your highfalutin, special-needs engine requires 89, you might be able to use 87 rated E10 in total safety. Plus, that way, you'd be stickin' it to The Man, who keeps tryin' to tell you what numbers you can and can't use. Who does he think he is, The Count? You go ahead and stick your 87 octane right in his craw and pump it until it goes "click."

Read more: 6 Car Myths That Cost You Money Every Year | Cracked.com
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Old 03-05-2012, 04:49 PM
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My last boat had 10:1 ratio motors and required 93 octane.......I've gotten tired of trying to explain to people that your engine does NOT make more power by simply putting higher octane fuel in it.
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Old 03-05-2012, 07:25 PM
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One reason to use premium fuel is because it has more detergent additive like Techron to keep valves and pistons clean. But the higher octane does nothing unless your engine is knocking.
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Old 03-05-2012, 07:35 PM
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Check my history I have been tellling this story for a good ten years. Veyr few engine sneed the higher stuff. the only reason I can think for most boaters and small engine guys to use higher octane stuff is it MAY last longer because the hi test has more ethanol (and yes less BTU's) and over time it evaporates first and the more you have to begin with the more you end up with.
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