Best 20W-50 for marine engines???

[Alex D]

I have so far been using Mercs 25W-40 in my twin 8.1S inboard engines (same as 496MAG). I would like to avoid the high cost f the Merc oil, but need something in the 20W-50 viscosity. I tried 15W-40, but it's too thin and oil pressure is only at 20-30 PSI. With the 25W-40 il pressure is 40-50 psi running and 20-40 psi idle depending on oil temps.

I am especially looking for a stout additive package in a good dinom oil.
Any recommendations???

 

[dwendt44]

Wal-mart has been carrying QuickSilver outboard oil, don't know about the stern drive stuff.
Marine oil is blended different that on road auto oil.
Marine engines have no air cleaners and no catalytic converters to worry about, but they are faced with higher corrosion problems, and the like.
Whether a outboard oil would work for you is a question I can't answer, and most outboard oil(4 stroke, of course) is 10W-30.
Mobil 1 15W-50 is reasonable at Target, some stores have it on clearance(low sales volume); you might try that.
My 2¢

 

[JonS]

I think if i had to use a 20w-50 in mine, i would go with Castrol GTX first, then Havoline.

 

[TooSlick]

The Mobil 1, 15w-50 isn't any cheaper than the OEM Merc oil, but it will hold up better. The 15w-50 has a much more robust add pack than the 30wt, Mobil 1 offerings.

Another excellent product in the same price range is the Amsoil 15w-40/AME. I have experience with that oil in the 7.4L Mercruiser engine and the oil I tested after 125 hours of use (37' Searay) had plenty of life left on it.

If you're hard over in the dino idea, the Valvoline, straight 50wt racing oil would be my choice.

TS

 

[Brett Miller]

Pennzoil 25W-50 Racing oil would work well.

 

[KBFXDLI]

I would not switch because the quicksilver oil has a more robust additive package especially for corrosion & shock protection. I am on my 4th set of GM big block marine engines and have tested the oil on numerous occasions and every time the TBN is higher at the end of season with the quicksilver than my buddy who has the identical boat and is using automotive synthetic 20w50. I have had nothing but excellent results from quicksilver and if you shop around you can find it discounted. My $.02

 

[JimG]

Here's another vote for Merc 25w40 oil. It's the best I've seen for marine engines.

 

[Donald]

KBFXDLI - does the TBN start out the same for the oil you and your buddy use? Same number of hours for you and your buddy during the season.

Merc 25W40 is a blend of two different weight oils, no viscosity modifiers.

Alex D - what 15W40 did you try where you got low oil pressure? Have you tried a diesel/gas rated 15W40 like Shell Rotella T.

 

[Steve S]

Try a straight 40 wt. hdeo.

 

[Cicero17]

My 2005 Searay 180 I/O (bought new in Feb) gets Quicksilver 25w-40 synthetic blend only, even though the price is outrageous. I use the Quicksilver or Merc oil filter too, I should cut one open some day. The oil is cheap compared to how the boat sucks up gasoline. Still, I don't know how I ever got by without it. I have not seen my flavor of Quicksilver at Wallyworld yet.

The only other option that could be worth considering is making your own synthetic blend of RL 15w-50 and Quicksilver 25w-40 dyno. Its unlikely I will try that one either.

Don

 

[t-squared]

I agree with TooSlick on the Amsoil 15w-40. A uoa after 108 hours of use in our 454Mag showed it had a lot of life left in it. One thing to remember, all of our marine engines are tuned on the rich side due to the loads and rpms we make them endure. This makes fuel dilution one of the big things the oil has to fight.

AlexD, there isn't any reason why your stock engines need a 50wt to keep them alive and happy. Tons of big blocks last a lot of hours on 40wt oils- dino or synthetic.

Here's a link to a bunch of suitable oil to use in your 8.1 stump pullers. Granted, some of the formulations have changed a bit, but you can still see there isn't anything special about the Merc oil. It's just a run of the mill heavy duty oil. Boat Oils

 

[KBFXDLI]

Quote:

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KBFXDLI - does the TBN start out the same for the oil you and your buddy use? Same number of hours for you and your buddy during the season.

---

LOL good point....maybe I am biased but sometimes my boat sits for a month at a time and I have been using this oil since the mid 1980's and never had any issues so I'm all about if it aint broke...don't fix it. Easy peasy 4 measy.

 

[nooil]

I would not use any oil that is not marine specific due to corrosion and other issues specific to these type of engines.

 

[TimVipond]

What oil requirements does your owners manual list? Take a look at Amsoils 10W40 Marine oil. https://www.amsoil.com/lit/databulletins/g2133_rev6_05.pdf It's not a truck or car oil, it is a synthetic marine oil.

Formula 4-Stroke® Marine Synthetic Motor Oils are
certified by the National Marine Manufacturers
Association (NMMA) for use in four-stroke outboard
motors. These high quality oils demonstrate outstanding
performance, exceeding the NMMA “FC-W” (Four Cycle -
Water) specification requirements. Formula 4-Stroke® Marine
Synthetic Motor Oils fulfill the warranty requirements of four-stroke outboard motor manufacturers.

 

[dwendt44]

Merc oil filters used to be made by AC. Don't know who makes them now.
Hopefully it's Purolator or Champion.

Mobil-1 EP 15-50 is a bit thicker than the regular M-1 15-50, and Wal-mart(at least around here) is carrying it again.
(both 15-50s).

 

[Turk]

I use the Amsoil 4-Stroke Marine 10-40. I absolutely swear by it - the 140 HP Suzuki 4-Stroke sings with it in.

Will not go back to any other oil.

I highly recommend the Amsoil.

 

[Steve S]

Is the 15w/40 oil pressure of 20 to 30 psi at idle? What is the oil pressure at wot when the oil is at operating pressure?. How can you worry about the $$$of the oil ? What about the gallons per hour of gasoline?

 

[Steve S]

I ment the oil is at operating temps .