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View Full Version : gas -89 or 91 octane?



pjw
08-17-2009, 03:42 PM
i was just reading owners manual for Indmar 325 in my 09 LSV -- states 89 octane with ethanol was ok -- anyone running 89 with 10% ethanol -- service told me to stick to 91 octane with 0% ethanol as ethanol breaksdown lining on hoses?

Razzman
08-17-2009, 03:54 PM
Do not run ethanol if you can avoid it. It causes all kinds of things including the dreaded vaopr lock.

sandm
08-17-2009, 05:38 PM
we have one station out here that's not ethanol blended that I have seen..
I run 89 and ethanol blend and been ok. had a couple issues with vaporlock, but a bit of water on the pump fixes it right up..
ethanol does break down parts of your fuel system if it isn't designed for it, but not in the % being sold today. lots of guys I know are switching to e85 in their turbo'ed 4bangers, but it requires a lot of replacement parts and a new tune.

funny how some think running higher octane makes your engine run better. run the minimum octane your owners manual recommends unless your engine is high compression or force fed. any more and you're pissing money away..

brenpire
08-17-2009, 06:00 PM
I'm with ED G. in Ontario,Canada you can't get away from ethanol fuel. never had a problem. had to change a fuel filter recently, but that could be anything.

Like sandm says. unless your engine is designed for higher octane (higher compression ratio)you are wasting your money. the higher the octane rating the higher the flash point of the fuel. your engine may actually run rougher with higher octane.

Unless you have an older engine with carbon build up. the carbon can actually create higher compression in the engine. if that happens higher octane will help you avoid engine knock.

Razzman
08-17-2009, 06:45 PM
I get away with it because we don't have it in California! Well i shouldn't say that, there are 10 E85 stations! WhooHoo! But wait, 3 are fed gov only facilities and the rest are scattered so it's useless to me anyway even though my '07 GMC Sierra is flexfuel. Useless. :cool:

sandm
08-17-2009, 10:59 PM
lets not confuse regular gas with the 10% additive and e85, which is 85% ethanol(and a much higher octane rating than premium).. e85 will do nasty things quickly to a motor as most injectors can't spray enough for the programmed fuel curve. engine operates lean and goes bang :)

be careful switching to e85 in your truck if you have not run it. I have seen where the e85 is different fuel and will attach itself to the gunk in the bottom of the tank. plan on replacing 2-3 fuel filters in the first 500 miles of switching if you have 30-50k on the truck, then the resulting 20% decrease in fuel economy due to the burn factor..
it's much higher octane though. truck will run much quicker :)

Lawdog
08-18-2009, 11:43 AM
lets not confuse regular gas with the 10% additive and e85, which is 85% ethanol(and a much higher octane rating than premium).. e85 will do nasty things quickly to a motor as most injectors can't spray enough for the programmed fuel curve. engine operates lean and goes bang :)

be careful switching to e85 in your truck if you have not run it. I have seen where the e85 is different fuel and will attach itself to the gunk in the bottom of the tank. plan on replacing 2-3 fuel filters in the first 500 miles of switching if you have 30-50k on the truck, then the resulting 20% decrease in fuel economy due to the burn factor..
it's much higher octane though. truck will run much quicker :)
So if your vehicle can take E85 would you say it would be wise to use it every once in awhile to clean out the tank?? I have an '08 Tahoe that I bought at the begining of '08. I've only put 10,000 miles on it in 1.5 years. When I first got it I used E85 for the first few months but found it wasn't economical in my area and switched back to regular.

sandm
08-18-2009, 12:46 PM
personally, I'd continue to use regular gas. e85 here doesn't make economic sense factoring in the lower fuel economy compared to the cost..
if you don't plan on using e85 regularly, then don't worry about it. normal sediment that is in everyone's gas tanks.

pjw
08-18-2009, 03:26 PM
i never use e85 in my SUV as price vs gas milage makes no cents --
As for my LSV -- i would love to run 89 octane with 10% ethanol -- from owners manual recommendation and this thread i am switching to 89 octane from 91.

thanks

Wake Master
08-18-2009, 07:33 PM
The engines do have knock sensors so even if you had to run 87 octane in a crunch it would not be a problem. You may loose a little performance. You are better off to use fresh 87 octane than old 89 octane! I personally us 89.