89 octane gas performance

[ccckirch]

Consider me a natural skeptic as car engines show no difference in performance. However, I am convinced that my 01 Johnson 90 performs better with mid-grade gas vs. regular gas. Any opinions on the matter?

 

[tx1961whaler]

Re: 89 octane gas performance

If you think that it performs better, then that is all that really matters, isn't it? There's not a person here that can tell you that your particular motor does or does not run better with 87 or 89 octane in it, as they are not there to observe the motor or experiment with it.

 

[64osby]

Re: 89 octane gas performance

I get about 2 MPG better using mid grade in my 1992 Caprice wagon, although I run regular most the time. I also only use mid grade in all my small engines. Ever since switching i have never had a problem with plug fowling or any other issues. I have a friend that runs a lawn mower dealership, he states only run midgrade in your small engines.

I know that others here will state there is no difference, but my .02 says run mid grade.

My 1967 Merc 500 loves mid grade, 8 years that I have owned it I have never had to touch the motor, or the carbs. Knock on wood

 

[Howard Sterndrive]

Re: 89 octane gas performance

I am convinced that my 01 Johnson 90 performs better with mid-grade gas

what is "performs better"?

 

[Vic.S]

Re: 89 octane gas performance

Mr Evinrude, Him say, "Current recommendations are to use a minimum of 87 octane, 89 octane is preferred. "

See http://www.evinrude.com/en-US/Owners-Center/FAQ/OilAndFuel#qst4

Our bog-standard unleaded in the UK is 95 RON, that's 90-91 on your AKI rating.

 

[steelespike]

Re: 89 octane gas performance

Have a friend with an early 60s Sears/Mcculloch 14? Factory suggested 89 octane
He ran 90 as it was all that was available.He swore it idled smoother and started easier than 87. That said I feel that if an outboard rated for 87 is tuned right and has no issues ie: carbon etc it should run right on 87.There are any number of auto engines rated for 87 in the late 80s that will knock on 87 even when new and require 90 to eliminate knock.Ford Ranger 4 cylinders are one.

 

[54fleetwin]

Re: 89 octane gas performance

you guys need to read up on what high octane actually does.

The higher the octane, the slower the burn.
Higher octane is needed on engines with lots of timing advance or higher compression ratios to avoid detonation.

Running higher octane than needed only hurts performance since it burns slower.

Run what the manufacturer recommends or higher if you have done mods like shaved heads, tuned exhaust, ect.

There is lots of good reading on the net about this subject