What fuel to run?

[SkaterRace]

I have a 2019 Mercurty 225XL. Been giving it marina fuel this whole year and last year I ran 87 (regular) gas in it as that is what the manual said. For next year I'm planning on not buying much fuel at the marina and most at a gas station on the sie of the road (way cheaper and less wait). I've always heard that you should run premium in outboards. If the manufacturer is 87 but also no-ethanol which is premium. Which do you go with?

 

[cyclops222]

Really a tough question to answer. Reasons
If you have stations with watery tanks ? Place sells low grade as a higher grade ? Adds water to increase profits ?

 

[SkaterRace]

Really a tough question to answer. Reasons
If you have stations with watery tanks ? Place sells low grade as a higher grade ? Adds water to increase profits ?

There are a few stations around town known for watery tanks. I avoid them and go to ones I know are a bit better. Typically you don't get much mixup in terms of grades from what I've herd but then again I can't tell much difference most of the time.

 

[KD4UPL]

So the manual calls for 87 octane? I'd run 87 octane ethanol free. You can buy that all over the place here in VA. It's what I use. Is it not available where you are?

 

[SkaterRace]

So the manual calls for 87 octane? I'd run 87 octane ethanol free. You can buy that all over the place here in VA. It's what I use. Is it not available where you are?

87 here contains up to 10%. Only ethanol-free is 91/premium

 

[KD4UPL]

Then I'd buy 91 ethanol free at the gas station.

 

[SkaterRace]

Then I'd buy 91 ethanol free at the gas station.

Makes sense thank you.

I was leaning that way from my previous experience but when I read 87 I figured it was right. I did not know 87 ethanol free existed as I've never seen or even heard of it.

 

[boscoe99]

I have a 2019 Mercurty 225XL. Been giving it marina fuel this whole year and last year I ran 87 (regular) gas in it as that is what the manual said. For next year I'm planning on not buying much fuel at the marina and most at a gas station on the sie of the road (way cheaper and less wait). I've always heard that you should run premium in outboards. If the manufacturer is 87 but also no-ethanol which is premium. Which do you go with?

I have never heard of gasoline with an 87 octane rating as being premium.

I don't believe that Mercury says no ethanol.

You can't go wrong by following the manual.

The pumps usually state "may contain up to 10% ethanol". Based on the luck of the draw you might get 87 octane with 0% ethanol."

 

[SkaterRace]

I have never heard of gasoline with an 87 octane rating as being premium.

I don't believe that Mercury says no ethanol.

You can't go wrong by following the manual.

The pumps usually state "may contain up to 10% ethanol". Based on the luck of the draw you might get 87 octane with 0% ethanol."

87 is not premium sorry for the confusion. Here the only ethanol-free is premium which conflicts with 87 which is up to 10%.

Interesting I could have sworn that the manual said ethanol-free when I read it before. Checking the Mercury site (not manual) it says E10 (so 87 here) is fine.

 

[airshot]

Use the grade your mfgr recomends...without question ! A couple ounces of fuel stabilizer removes any issues that you might have with E fuels. Using a higher octane fuel than your engine calls for can actually reduce engine performance. Many articles have been written by engine engineers about this use of higher octane fuels....simply put...you are making your engine less efficient !!

 

[SkaterRace]

Use the grade your mfgr recomends...without question ! A couple ounces of fuel stabilizer removes any issues that you might have with E fuels. Using a higher octane fuel than your engine calls for can actually reduce engine performance. Many articles have been written by engine engineers about this use of higher octane fuels....simply put...you are making your engine less efficient !!

Thanks, I guess I was mainly going off the old thought of outboards need premium. 87 it is then. Cheaper so bonus excuse to go out more.

 

[airshot]

Thanks, I guess I was mainly going off the old thought of outboards need premium. 87 it is then. Cheaper so bonus excuse to go out more.

Whatever fuel you use, be very careful where you buy it.....most fuel issues start at the sellers place. In our area we have monthly fuel tank inspections on the in ground tanks and the findings are available for public inspection. You would be surprised at how many brand name fuel stations lack maintenance on their fuel tanks !!

 

[boscoe99]

Use the grade your mfgr recomends...without question ! A couple ounces of fuel stabilizer removes any issues that you might have with E fuels. Using a higher octane fuel than your engine calls for can actually reduce engine performance. Many articles have been written by engine engineers about this use of higher octane fuels....simply put...you are making your engine less efficient !!

Why is that?

 

[boscoe99]

No mention by Mercury Marine as to performance degradation when using gasoline with an octane rating above 87. Which is the minimum. As in, higher is OK. Less is not.

 

[airshot]

Why is that?

Because premium fuel burns slower where lower octane fuel burns faster. When an engine is set up for 87 octane fuel and the owner uses slower burning 93 fuel, the engine will loose some effiency. Look up any of the numerous written on this issue. An engine will never create more power by going to a higher octane fuel unless it gas been setup to do so. Will it hurt anything ...no...but you are throwing money away.

 

[boscoe99]

Interesting.

I ran a Yamaha F70 first with gasoline rated at 87 octane and then again with 93 octane. Highest I could find. There was no difference in top speed. Fuel burn rate was the same. Seems as if the slower burning 93 octane would have produced less power.

 

[Chris1956]

Your motor is made to run on regular fuel with or without alcohol. I would run fuel from a high volume gasoline station, as these usually have fresh gasoline and are without water in the fuel.

Stabilizer can be useful for off-season storage but is unnecessary if you use the boat every couple of weeks or more during the season.

 

[dingbat]

Interesting.

I ran a Yamaha F70 first with gasoline rated at 87 octane and then again with 93 octane. Highest I could find. There was no difference in top speed. Fuel burn rate was the same. Seems as if the slower burning 93 octane would have produced less power.

Two of my three vehicles give HP and Torque as a function of octane.

Both are GDI, high compression, turbo charged engines that support 87, 88 (flex) and 93 octane.

The manual goes on to state the fuel itself doesn’t cause the increase. The increase is due to the use of more aggressive tunes when running the higher octanes. Guessing they monitor the knock sensors to adjust the tune to the fuel

I’ve only had the Mazda for a week so not much experience, but the Ecoboost in the truck gets noticeably better fuel economy on 93 octane

 

[tpenfield]

I would not agonize over using 87 from the gas station. It sounds like the engine will be fine.

 

[airshot]

Interesting.

I ran a Yamaha F70 first with gasoline rated at 87 octane and then again with 93 octane. Highest I could find. There was no difference in top speed. Fuel burn rate was the same. Seems as if the slower burning 93 octane would have produced less power.

It does....may not be noticeable in your setup. No one says it will make a big difference but when your motor needs to work its butt off, always best to use what is designed for it !! Go talk to some racing folks, they will tell you the differences when the proper octane fuel is used. Just because it might not be apparent in your situation, doesn't mean it is good for it.