Oil 4 stroke Mercury 115hp

[Captf22]

4 stroke oil, New Mercury 115hp 10w-30 or 25w-40 Synthetic Blend any opinions?

 

[Chris1956]

That motor likely requires a FC-W oil. Any oil rated as such is acceptable. Automotive multivis oils are generally not recommended.

 

[jimmbo]

Welcome to iboats
Mercury markets several Oils for your engine. Can't go wrong with them, especially during the Warranty Period.
As mentioned above, avoid Auto Oils if you can, as they are speced/blended for Auto/Light Truck Engines, and Marine Engines operate in under different conditions

 

[racerone]

Motors are too expensive to skimp on oil.-----Use the factory recommended product.

 

[muc]

Since 2014 10w-30 has been recommended for the 115.
Make sure to use the Synthetic Blend
You can use the 25w-40 if your operating in a hot climate, check your owners manual.
Make sure to use the Synthetic Blend

 

[Lou C]

I have used the expensive Mercury/Quicksilver oil and gotten excellent oil analysis results on my old 4.3 that still has the original 38 year old short block.
Here's a bit of info that pertains to inboards more than outboards, for others who might be interested:
The 25/40 syn blend, is approved for Cat Converter engines and as such has lower levels of Zinc and Phosphorous (below 1000 ppm of each).
The 25/50 syn blend is approved for high performance outboard and in my oil analysis, it came up with 1300 ppm of each, I used it for a few years just to see what the difference was on the oil analysis.
So if you have a flat tappet inboard, you might want the 25/50 because it has more zinc.
My engine has a roller tappet cam so I can use the 25/40 syn blend.
Another option, for those who want high zinc but at a much lower cost than the Merc 25/50 syn blend (which has gone up in price from $52 a gallon to a sky high $66 a gallon), is Valvoline VR-1 20/50, this has 1300 ppm of both zinc and phosphorous and is less than half the price of the Merc oil at $27 a gallon. Might try this after I have used up all my Merc oil and see what the oil analysis shows.

 

[muc]

I have used the expensive Mercury/Quicksilver oil and gotten excellent oil analysis results on my old 4.3 that still has the original 38 year old short block.
Here's a bit of info that pertains to inboards more than outboards, for others who might be interested:
The 25/40 syn blend, is approved for Cat Converter engines and as such has lower levels of Zinc and Phosphorous (below 1000 ppm of each).
The 25/50 syn blend is approved for high performance outboard and in my oil analysis, it came up with 1300 ppm of each, I used it for a few years just to see what the difference was on the oil analysis.
So if you have a flat tappet inboard, you might want the 25/50 because it has more zinc.
My engine has a roller tappet cam so I can use the 25/40 syn blend.
Another option, for those who want high zinc but at a much lower cost than the Merc 25/50 syn blend (which has gone up in price from $52 a gallon to a sky high $66 a gallon), is Valvoline VR-1 20/50, this has 1300 ppm of both zinc and phosphorous and is less than half the price of the Merc oil at $27 a gallon. Might try this after I have used up all my Merc oil and see what the oil analysis shows.

O.P. says this is a new Mercury 115HP Outboard.
I would highly recommend using what the owners manual has in it.
Application determines specifications. Google the Motor Oil Geek on YouTube. That Lake Speed Jr. know his stuff!

But yes the prices blow my mind. I'm back in the business working the parts counter and I sell these oil change kits almost everyday. Seems that most Minnesota outboard owners wait until spring to change their oil.
$110 plus tax for 5 QTs, filter and the drain hose! I ask if they want to do their gear lube? Yup that's $41 for the QT of high perf 90w, pump and a couple of plug gaskets.
$165 for a DIY oil change?

 

[jlh3rd]

I bought a new Merc 115hp CT in 2021. 10w-30 Merc/quicksilver synthetic is recommended. I'd not deviate from that especially under warranty. I don't have my manual in front of me, but 20w-50 I think is acceptable.

 

[Lou C]

IIRC when Merc came out with their 25/40 mineral oil they also said that if it wasn't available you could use straight 30 in cooler temps, straight 40 in warmer temps and 20/40 or 20/50 but this is all for inboards.
I agree if I had a modern outboard I'd just use what they advice, given the cost of these motors, why experiment.
With my old one, I have used:
Delo 400 straight 30
Delo 400 straight 40
Merc/Quicksilver 25/40 mineral oil
Merc/Quicksilver 25/50 syn blend
the Merc oils actually did better on the oil analysis than the Delo straight weights did and that was a surprise to me
I am curious about the Valvoline VR-1 20/50 though, for the price might be a good choice, for older gas inboards esp those with flat tappet camshafts.

 

[airshot]

O.P. says this is a new Mercury 115HP Outboard.
I would highly recommend using what the owners manual has in it.
Application determines specifications. Google the Motor Oil Geek on YouTube. That Lake Speed Jr. know his stuff!

But yes the prices blow my mind. I'm back in the business working the parts counter and I sell these oil change kits almost everyday. Seems that most Minnesota outboard owners wait until spring to change their oil.
$110 plus tax for 5 QTs, filter and the drain hose! I ask if they want to do their gear lube? Yup that's $41 for the QT of high perf 90w, pump and a couple of plug gaskets.
$165 for a DIY oil change?

Wow......just another reason to stick with my old two stroke, looks and runs like new, two stroke oil is 22 bucks a gallon for Pennzoil...just for fun, I compared mine to a brand new Merc of same hp. New motor uses 1.5 gallons per hour less than my 1992 per factory quotes. Not sure I will live long enough to make up enough savings to pay for a new motor !

 

[Mc Tool]

Mmmmm I wonder who makes that Mercury quicksilver oil for them .

 

[jimmbo]

One of the Oil Companies, but they refine/blend it to Mercury's Specs and uses an Additive Package that is also Specific to Mercury's Specifications...

 

[jlh3rd]

oil is oil....got it. But when you have a new motor that cost $12,000 you're taking a huge gamble under warranty by not following the owner's manual, especially when it comes to oil specs.
And I do believe there is some truth to manufacturers engine designers specific oil spec requirements for their engines.

 

[racerone]

Oil is NOT all the same.

 

[muc]

IIRC when Merc came out with their 25/40 mineral oil they also said that if it wasn't available you could use straight 30 in cooler temps, straight 40 in warmer temps and 20/40 or 20/50 but this is all for inboards.

IIRC that was about 4 decades ago. Information like that has been changed many times since then.

 

[airshot]

It is all about the additives that are in that oil. If your under warranty, definitely use what the mfgr specifies, after that, your on your own.

 

[Mc Tool]

I have never bought a new motor so Im not tied in by any warranty .
I have had this argument/discussion many times . While I understand that manufacturer spec'ed oils are good oils to use because any manufacturer (that doesnt go to the trouble of making their own oil ) will simply tell some other oil company what they want in their motors and for the average guy it makes the decision easy to get a suitable oil in their motor and the peace of mind that goes with that, But ,as mentioned above the bastards know how to charge for this privilege . Others have said that marine four stroke oils have special additives for marine use.........maybe they do but Im blowed if I can see any real difference in how the motor is used as opposed to a car engine , I mean I live on the coast ....should I use marine oil in my car ? My car motor often spends hours at cruising rpm ,with stops and starts , full power blasts when overtaking other vehicles bla bla bla .
At twice the price of a good quality car oil (Im not getting into the mineral verses synthetic thing here ) Im happy to leave them on the shelf and pop down to Napa and buy a good oil . Both my cars like 5w or 10w oil.......and so do both my outboards .....so they all get the same stuff , and because it also pours nicely into my quads, lawn mower and pressure washer they get it too. I save a lot of money by buying oil in 20L lots when its on special ( often near ½ price).
I do run short change intervals , like 7-10,000kms in the cars ( hardly any short trips) and so far both 4 stroke outboards wouldnt do 10 hours on the meagre amount the sump holds.Factory suggests 100 hours which to me is way to far on something that holds only 2L of oil
I dont believe anyone will come to grief using decent automotive oil in an outboard . I get that anyone running a boat repair shop has to be seen to be using top quality stuff and its so easy to show the customer this is so by using factory branded products.
Who else here would remove the ohc cam/rocker cover and tip oil on the cam and valve gear before starting after a long-ish period of no use..