91 Octane pure gas Or 10% Ethanol 87 Octane?

[nitroman12]

Mercury techs please weigh in. What is the highest octane recomendation on a Mercury 250 Pro XS?

[06 SB]

This question comes up a lot. I run 87 with corn oil. No issues as long as you use it regularly. I treat it with Don's cocktail too. It just isn't a big deal. I would worry more about carbon build up running 91 unless your motor calls for it. It really is up to you and what makes you feel better.

[hooken203]

If it were my choice I would use the 91 so I could stay away from the ethanol. If you use your fuel up quickly then ethanol is fine. Many people run it for ever and never have an issue. But it is an absolute fact that it will collect moisture right out of the air and this can be a problem. Also the ethanol is corrosive and those problem you may not see right away. The carbon issue well it may be a fact but if you run your boat hard and or use Dons mix it won't be an issue

[Savage]

Mercury techs please weigh in. What is the highest octane recomendation on a Mercury 250 Pro XS?

What year?

[Chautauquanuy]

I am following this thread as well. I can drive ~15 miles rountrip to get pure gas at 91 Octane. Have a '14 Optimax Pro XS 150 hp.
Interestly every year there are more pure gas stations showing up.

Is there any sense in running mixed gas in your boat fuel tank that contains 50% 87 octane ethanol gas and 50% 91 octane pure gas? That would increase octane and decrease ethanol over the ethanol 87. Just don't want to do any harm.

[nitroman12]

2014

What year?

[Savage]

I would run 87 with 10% ethanol with NO FEAR. The motor was programmed by Mercury to run on this fuel. If you have the correct fuel lines, 10% ethanol won't hurt anything.

[nitroman12]

Thanks Guys

[gehol]

Mercury techs please weigh in. What is the highest octane recomendation on a Mercury 250 Pro XS?

But, to answer your question, there is no highest octane recommendation. Mercury only gives you the minimum requirements.

[hooken203]

I would suggest you do a search on fuel system damage caused by ethanol.

[mn_bowhunter]

Savage - what year would it make a difference?

[Savage]

I would suggest you do a search on fuel system damage caused by ethanol.

Yes let us know what you search results are for "fuel system damage caused by ethanol" on a 2014 250 ProXS........Because that is what we are talking about here.

87 octane with 10% ethanol will NOT damage the fuel system on a 250 ProXS.

[hooken203]

It will if there are certain metal or plastic parts in the system and I am not talking about just the engine. But yeah I bet all the boat and marine engine engineers got that covered because they are far and away better than all the other engineers in the world.
Yes please do a search on use of ethanol use in a 2014 Mercury engine by all means.

[clayshooter100]

Yes let us know what you search results are for "fuel system damage caused by ethanol" on a 2014 250 ProXS........Because that is what we are talking about here.

87 octane with 10% ethanol will NOT damage the fuel system on a 250 ProXS.

+1

[EuropeanAM]

Yes let us know what you search results are for "fuel system damage caused by ethanol" on a 2014 250 ProXS........Because that is what we are talking about here.

87 octane with 10% ethanol will NOT damage the fuel system on a 250 ProXS.

+2

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