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Old 05-26-2010, 06:27 PM
emtfire148186 emtfire148186 is offline
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What octane to use

I have 2 scag walk behinds that i use 89 in. Is this ok or should i use 91?

I use 91 in all my 2 stroke engines
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Old 05-26-2010, 06:40 PM
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punt66 punt66 is offline
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i use 87 in everything. No issues. If its not detonating then your just wasting your money.
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Old 05-26-2010, 06:42 PM
emtfire148186 emtfire148186 is offline
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OK thanks....I'll stick with what i use now
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Old 05-26-2010, 07:31 PM
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clean_cut clean_cut is offline
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To my knowledge, you only need the 89 or higher in 4 mix equipment, such as some stihl blowers and trimmers.
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Old 05-26-2010, 08:50 PM
emtfire148186 emtfire148186 is offline
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Ok great...Thanks for the info
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Old 05-26-2010, 10:24 PM
johnwon johnwon is offline
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From what I've read, if your engine is factory set or tuned to, lets say 87 octane, then using higher octane will have the same effect as slightly ******ing the timing. The higher the octane the more resistant it is to pre ignition. So in theory the position of the crank maybe just a little past the optimum position when the explosion takes place in the combustion chamber.
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Old 05-26-2010, 10:42 PM
emtfire148186 emtfire148186 is offline
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ok thanks for the info. I was told to use 91 before, but i wasn't sure about it. I been having problems with my walk behind backfiring. I was told that it would sometimes fire on only 1 cylinder. I did everything possible to try and fix it. tune up, coils, new gas, adjusted valves, cleaned carb about 5 times really good, compression is like 130-135 on both sides. the small engine mechanics cant find anything wrong. My buddy said switch to 91 or 93 to help clean it out. Just wanted everyone's opinion
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Old 05-26-2010, 11:10 PM
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i use 87 in the truck and mower and 91 in the 2 stroke stuff and the br600
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Old 05-27-2010, 12:16 AM
ajslands ajslands is offline
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I use diesel! But in my mowers I use 87
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Old 05-27-2010, 03:22 AM
topsites topsites is offline
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How many grades y'all got out that way?

Around here it's 87, 89 and 93...

Quote:
Originally Posted by johnwon View Post
From what I've read, if your engine is factory set or tuned to
These are carbureted engines, no computer.
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