FUEL and FUEL ADDITIVES for 4-Stroke Models EDITED 3/21/19

[EuropeanAM]

Please consult your owner's manual, or http://www.mercurymarine.com for the BEST recommendations on each of these items!

FUEL:
-All models- MAXIMUM ETHANOL CONTENT: 10%. Ethanol content may adversly affect engine performance.
-See "Mercury's View of Ethanol" on Sherm's board at: Mercurys take on Ethanol blended fuel

OCTANE:

-Standard 4-stroke Engine Models (Including V6/V8 Fourstrokes): 87 Octane
-Verado PRO Models: 87 Octane Minimum (improved performance with 91+ Octane)
-Verado 350 (new production model)- 91+ Recommended (89 minimum)
-Verado 350 SCI/Racing: 92 or above recommended
-Verado 400R: 92 or above recommended

Fuel Additive Recommendations:
-Stabilize fuel ANYTIME fuel will not be consumed and replaced within 15 days!!!
-Verado Models: Quickleen in EVERY TANK OF FUEL. You CAN combine Mercury QuickCare or QuickStor Fuel System Treatment & Stabilizer with Quickleen. Use the recommended "dose" of each product per the bottle instructions.
-Quickleen may be used in ANY Mercury engine- it helps to prevent/remove carbon buildup (primary purpose).

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"Mercury Component Cocktail"- for EVERY tank of fuel, whether or not your fuel contains Ethanol: (Chemically, this works much the same as the previously recommended (and now to avoid alcohol content) cocktail, and requires less components.) This is Don's Preferred "Cocktail":

-1oz Mercury QuickCare per 5 gallons fuel
-1oz Mercury QuickLeen per 5 gallons fuel
(If leaving fuel in boat for more than 30 days, Use Mercury QuickStor rather than the above Quickare- this will help protect against fuel degradation).

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Fuel Selection:

Make your fuel selections based on the following criteria, IN THE FOLLOWING ORDER:

-High Traffic, Top-Tier (Name Brand) Fuel
-Appropriate Octane Rating (see above info)
-Lowest possible ethanol content (NEVER to exceed 10%).
-While it may be preferable to utilize a fuel that contains lower (or no) ethanol, use of fuels that are SUBSTANTIALLY higher octane can result in decreased performance, decreased fuel economy, and potential for carbon buildup. Higher octane fuels burn SLOWER and COOLER.

[572 Fitter]

Thanks

[btsmbass]

Since verados have a knock crystal. Wouldn't higher octane fuel benefit all models? It is constantly adjusting timing.

[EuropeanAM]

Since verados have a knock crystal. Wouldn't higher octane fuel benefit all models? It is constantly adjusting timing.

Not necessarily the case. Some SPECIFIC models will benefit from higher octane fuel (the older Standard 275, all of the Pro Verado models, etc).

Knock sensor doesn't adjust timing- it signals the PCM as to whether or not KNOCK is occurring. PCM then uses it's programming to determine whether timing adjustment is necessary.

Models SPECIFICALLY designed this way (such as those stated above) are programmed to "optimize" timing to the highest (SAFE) level, based on knock data received.

Standard Verado Models that were NOT equipped with this programming will simply monitor for knock- if knock is PRESENT, it will REDUCE timing (and/or ADD FUEL) to protect the engine.

[jammerone]

Just saw the octane recommendation for the new 4 stroke, I live on lake and all marinas sell now is 90 octane no ethanol fuel, supposedly. So will this damage the new 4 strokes?

[EuropeanAM]

Damage- no. It may, however, result in decreased performance, decreased fuel economy, and potential for carbon buildup.

[mkm]

Guess I need to quit using the 93 non ethanol (175 ProXs 4 stroke). Would you use 89 octane, non ethanol or use 87 octane with ethanol? Stores near me has 87 and 93 Octane, non ethanol.

[EuropeanAM]

Guess I need to quit using the 93 non ethanol (175 ProXs 4 stroke). Would you use 89 octane, non ethanol or use 87 octane with ethanol? Stores near me has 87 and 93 Octane, non ethanol.

Octane Requirement/Number should have higher priority than "no-ethanol". Since 87 Octane is the recommended fuel, I would stick with that, meeting the criteria in the listed order:

Make your fuel selections based on the following criteria, IN THE FOLLOWING ORDER:

-High Traffic, Top-Tier (Name Brand) Fuel
-Appropriate Octane Rating (see above info)
-Lowest possible ethanol content (NEVER to exceed 10%).
-While it may be preferable to utilize a fuel that contains lower (or no) ethanol, use of fuels that are SUBSTANTIALLY higher octane can result in decreased performance, decreased fuel economy, and potential for carbon buildup. Higher octane fuels burn SLOWER and COOLER.

[TritonTRXV8]

Been running 89 guess ill switch to 87.

[jrbdad]

I have taken apart many a engine (car/truck/motorcycle, not boat) that has been run on high octane fuel. The fuel burns slower and sometimes that causes all the fuel to not burn correctly and will cause excessive/premature carbon build up. Have evan seen some engines have valves stick or no seal because of all the buildup.

[fly by night]

Good information, thanks for sharing!

[jrbdad]

I took apart a engine from a 2002 Ford Ranger that only had 24,000 miles on it because of running issues. When I go it apart the rings were stuck in the piston groves and broke all to pieces. They stuck because of carbon buildup. Younger girl drove the truck. Her father said he told her to always put premium in it and he would put addative
I it sometimes too. She drove it very easy. Ford engineer looked at it too and agreed that the high octane fuel accompanied with easy driving cause the build up and rings sticking.

I do not think that would happen in a boat (feel like bigger load on engine and runs wide open from time to time), but is an example of what CAN happen. Crazy isn't it.

[RGK456]

My dealer said to not mix ethanol blended fuel with non ethanol fuel, said it causes problems, thoughts?

[bloodman]

My dealer said to not mix ethanol blended fuel with non ethanol fuel, said it causes problems, thoughts?

Thats kinda strange aint it since ethanol is blended in gasoline anyway.

[EuropeanAM]

My dealer said to not mix ethanol blended fuel with non ethanol fuel, said it causes problems, thoughts?

The "Book" answer is that he is correct. That being said- MOST problems with that stemmed from intermixing of MTBE based fuels (should all be LONG gone by now) with Ethanol Blended fuels.

My recommendation is that if you must make a switch back and forth, do it with a LOW fuel level, burn out the new fuel promptly, and refill the tank again. In other words... don't leave it in the tank (mixed) for a long period.

MOST fuels are blended with ethanol at the Depot, right before (or as) they are going into the transfer truck. Prior to that, same fuel.

[Cbump]

Will be buying some quickare and Quickleen for my pro xs 4stroke!

[carp_mstr]

I have been running 250 HP Yamaha SHO 4 strokes since 2010 and always ran Ring Free Plus ans Yamaha stabilizer but have ordered my new boat with the new Mercury 250 Pro XS 4-stroke and have a sizable amount of the Ring Free Plus and stabilizer left and wonder if I should use them in the Mercury?

[EuropeanAM]

While you certainly "could"... I personally would be inclined to make someone with a Yamaha a good deal on the products and use those that are recommended on your new engine.

[jimmybass2]

Hey Don... you were a great help with my ProXS 250 2 stroke and now I'm back in the game with 2021 ProXS 200 4 stroke...

Question.. Don's Merc Component Cocktail in Every Tank?

Thanks in advance,

[EuropeanAM]

Perfectly acceptable choice. See Post# 1