Premium Gas?

Good Morning Everyone! Yesterday there was a discussion on Ethenol in gas. A couple of guys said they used Premium gas in their outboards. Being clueless on the subject, I have a 07 merc 90 2 stroke. I have always used 87 octane in it and no fuel additive other than sta-bil. Should I be using premium gas AND a fuel additive? Please advise. Thank You!

I think you are fine with that motor. I’m about 90% certain your manual states 85 octane is the minimum required.

More good general info on ethonal from the Merc website:

Mercury Marine

-J.

While Ethanol does contain less energy per volume it is negligible in gasloline at 10% or below the total volume. You MAY see a percentage or two drop in economy.
Ethanol is actually an octane enhancer as well as a fuel so it is likely that if your local pump is using Ethanol enhanced fuel it is in all grades and probably at full 10% in premium fuel

.To find what Ethanol volume is in the fuel you use ask the station attendant. If they do not know they may have a pamphlet with the details or at the very least a 1-800 number you can call.
Usually regular contains 5% Ethanol while mid and high grade fuel contains 10%.

So again, if you are using these fuels in engines not designed for them, it is important that you use an additive to cope with the harmful effects. Check out my other post on Ethanol killing small engines.

Thanks

Ace

Also, here is what I do personally. (I had a 90 Merc a few years back and a 150 opti now.)

I run regular 87 all year. (10% ethonal) Then towards fall, I switch over to premium non-ethonal gas. Usually in the 95-97 octane range. I start running a can of sea foam with each tank until the season ends. If I park it empty or with a full tank, don’t matter. Never had a problem.

-J.

I read your post Ace, thank you for the detailed info

Thanks Ace!