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Posts: 360
Location: Tinley Park. Fish Cen IL. Bass & Vilas Cty.Muskie | I have a 1998 Johnson 150 motor. I have always used 87 Octane since engine was new. Can I use 91 Octane once in awhile and go back to 87 Octane ? Please explain. Thanks. |
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Posts: 247
Location: Uxbridge Ontario | if your engine can handle 87octane, switching to a higher octane grade is not detrimental. In some cases, the higher octane might not run as well as the lower octane (as is the case with some 2 stroke applications). This has to do with port and cylinder timing, firing order and some of that internal engine stuff.
This situation is not the same as running a lesser octane that required. If your engine called for lets say 91min., then only run a minimum of 91. Running a lesser octane than required can have serious detonation issues (deto) and can cause serious engine damage. The reason is, lower octane levels burn slower than high octane levels which in most cases create excessive heat buildup (especially on the head and exhaust ports and also unspent fuels that create exhaust chamber issues.
So to answer you question, running higher grades is ok. Typically if i have (what I'll call relatively old) gas in my tank, I will top it up with gas a few grades higher to bring it back to a respectable level.
Hope this helps/ |
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Posts: 582
| hometime is right. won't be an issue in your case. I have been doing that for years depending on what kind of gas is available for where i am. |
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Posts: 360
Location: Tinley Park. Fish Cen IL. Bass & Vilas Cty.Muskie | Thanks for your responses. I was up in Voyager National Park this past week and I took the boat out of the water to bring to the gas station to get the 87 instead of filling up at the dock with 91. I will know better next time. Have a Great Summer. Roy |
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87 Octane to 91 Octane and back to 87 Octane ?