Best gas for outboard

Ghost Rider 2

Seaman
Joined
Jan 27, 2006
Messages
56
I have been thining of what is the best gas for my outboard. The tag says to use gas with 89 octane rating. Mixed at 50/1 Locally I can get 3 grades of fuel. Reg. 87 mid grade 89 premium 92 to 93. My question comes up from checking out the way fuels sell. The fast seller is 87. The next is the premium. The slowest seller at a station is the mid grade 89 octane. I have always heard that fuel will loose octane sitting. If the mid grade moves the slowest than how much loss has there been? My thoughts are would you be better off mixing the 87 & 92 octane so that you would have a fresher fuel? Cost would average out about the same. What are others oppions?
 

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: Best gas for outboard

What make, model and year is your outboard, GR?<br /><br />Many of those labels refer to the technology of the time they were built. Gas has changed a lot in recent years.<br /><br />Almost all modern 2 stroke outboards run best on 87 octane unleaded. Most modern EFI 4 strokes can benefit from higher octane. If you have concerns about the gas aging, add Stabil to each tank.<br /><br />(239)
 

Ghost Rider 2

Seaman
Joined
Jan 27, 2006
Messages
56
Re: Best gas for outboard

I have a 1972 Mercury 140 Horse inline 6 cyl. I even wondered about running premium, but had thoughts of it carboning up.
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
Re: Best gas for outboard

My '02 owners manual says use a minimum of fresh 87 octane (R+M/2). I thought about running premium also, but I asked several filling station operators how much premium they sell and they said not much. <br /><br />Now you'd think there wouldn't be much evaporation of the more violatile particles that make up the higher octane fuel, in a quasi sealed tank buried in the ground at 55 degrees, but who knows. <br /><br />So I run the gas that moves the fastest....87.<br /><br />Mark
 
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