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Old 03-03-2014, 02:27 PM
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mapbike mapbike is offline
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Join Date: Mar 2010
Location: Central Texas
Posts: 5,379
Talking Re: Regular v premium

You are spot on here Agreen,

I also have actually been in a couple of friendly debates over the years about the octane issue, with people for instants running a 8.5:1 compression SM Block Chevy with a carb that was way to big like a Holley 750 dbl pumper and telling me they went down to Chevron and pumped a tank full of 93 octane and now they had all kinds of extra power and also could tell they were getting much better gas mileage.... LOL! I don't like to hate on people and I don't like to shoot people down but, anyone that knows the facts knows that that is all complete bunk and isn't fact at all and is only a placebo affect at best because in their mind they wont it to be the case so somehow convince themselves that it did make a difference.

I don't care what anyone runs in their engines, but it bothers me when they try to convince others of things that are flat out incorrect and may cause someone to spend more money and get their hopes up for no good reason.

I have had my china girl 66cc engines with compression so high that I could barely get them started because even with the clutch adjusted extra tight it would still slip and sometimes even skid the rear tire with my 200+lb self on it and I still run 87-89 octane pump gas with no signs of pre ignition and no other issues, I say run what you want but why spend more on fuel than you need to when the stuff is twice to high to begin with, and if you don't actually need a higher octane fuel you will possible decrease your engines power output and not increase it due to the higher octane fuel not burning as complete in the low to medium compression engine.

happy safe riding all...

Peace, Map

Originally Posted by Agreen View Post
Once again, to put the myth of high octane fuels to rest:

The higher octane number does not give any more energy content per unit of fuel. You will not achieve more power or fuel mileage, nor will there be any better effects of burning higher octane fuel in an engine designed for regular fuel.

It ONLY means the fuel is less likely to auto ignite, meaning that the air/fuel ratio will not detonate before the spark plug fires it. You only need higher octane when dealing with an engine that has a higher energy input in to the fuel, or a higher activation energy.

The higher octane fuels are harder to ignite, meaning if you do run them in an engine that will not detonate on a lower octane fuel, it will only lead to a more incomplete combustion. This WILL lead to more deposits in the engine, and you will get less power from the engine because of the incomplete combustion. On the inverse side, running a lower octane in a high compression or forced induction (turbocharged/supercharged) engine will give you detonation and auto ignition because the energy the engine is exerting on the air/fuel mix will be higher than the combustion energy required to combust the fuel before the spark plug fires. This can quickly destroy an engine.

So if you don't have a high compression engine and you're not experiencing knock, then don't use "premium" fuel. I use quotes around premium because I don't want people to associate higher octane numbers with being better. It's a myth.

I absolutely hate hearing people say that they fill up with "premium" every once in a while to keep the engine clean and healthy. They have no idea why they're doing so. Probably because they associate premium with terms like best, clean, healthy, etc.

If the premium fuel in your country really is filtered better, then get a good fuel filter and prove it. I seriously doubt it's anything more than another myth, but then again I don't know anything about how Australian refineries process their fuel, so I may very well be wrong. Im skeptical at best.
I dont always ride WOT, but when I do..I do my best to keep the rubber side down..Ride safely my friends!
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