Question about engine oil

[zippy83]

Hi All,

I have a new 2021 Mercury PRO XS 200 and I just got my oil changed (I did it myself). The manual states to use 25w-40 or 10w-30.. I went with the 25w-40 but recently one of my fishing buddies told me that his service said if you live in an colder region not to use the 25-40 and go with 10-30. He also mentioned that the operating weather temperature for the 25-40 should be above 40F. My question is is my boat is sitting in my garage that is not heated and we are currently at 3F for the past 5 days. Next week it’s going to be in the mid 50’s again, If I was to go out would that result in damage to the motor, since it was sitting in freezing conditions for a few days?

Thanks
Zip

 

[Scott Danforth]

you are fine, go boating

 

[Lou C]

If you’re starting with current temps in the 50s nothing to worry about. I’ve started my inboard running the same oil as cold as 45* with no problems.

 

[Chris1956]

Did you use a FC-W motor oil or automotive multi-vis? The FC-W oil is made specifically for four cycle outboards, and is supposed to be more robust for the heavier power requirements of the marine engine, versus an auto engine..

The word is that the automotive oil is too wimpy for the high stress use of a marine engine.

 

[paulswagelock]

The cold weather only thickens the oil while cold, and as soon as it warms up it thins again. you are absolutely fine.

 

[paulswagelock]

Did you use a FC-W motor oil or automotive multi-vis? The FC-W oil is made specifically for four cycle outboards, and is supposed to be more robust for the heavier power requirements of the marine engine, versus an auto engine..

The word is that the automotive oil is too wimpy for the high stress use of a marine engine.

Just not true. There are many automotive and diesel oils that would surpass the requirements set forth by the FC-W spec. I have read the spec, it is nothing special as far as the requirements set. What is obtrusive is the need to purchase a Yamaha outboard, then run it on the specified oil, just to tear it down to quantify wear. The business model to invest in meeting that spec just doesn’t make sense for the automotive oil segment with such small sales in the marine market relative to automotive applications.

 

[JimS123]

Your Mercury Marine Owner's Manual clearly states in writing what oil to use. It even goes so far as to specify the temperature range for each oil grade.

Your buddy must have read the manual.

If the temperature goes to 50, and assuming the engine warms up to that level, then you should not have a problem. I assume you used Mercury brand oil. I buy mine on EBay and it costs no more than wally oil.

 

[zippy83]

Did you use a FC-W motor oil or automotive multi-vis? The FC-W oil is made specifically for four cycle outboards, and is supposed to be more robust for the heavier power requirements of the marine engine, versus an auto engine..

The word is that the automotive oil is too wimpy for the high stress use of a marine engine.

I used Mercury oil from the dealership.

 

[zippy83]

Your Mercury Marine Owner's Manual clearly states in writing what oil to use. It even goes so far as to specify the temperature range for each oil grade.

Your buddy must have read the manual.

If the temperature goes to 50, and assuming the engine warms up to that level, then you should not have a problem. I assume you used Mercury brand oil. I buy mine on EBay and it costs no more than wally oil.

Yes the manual calls for both 10w-30 and 25w-40 and the service manager said that 25w-40 is a better oil.. but did not mention anything about the temperature. Anyway I do not go out fishing if the weather is below 45F.

 

[QBhoy]

Unusually for me…I’ve only just taken my outboard boat out the water this week. I’d normally be taking all the boats out before November usually. With the exception being this outboard powered boat. Great to keep her in a little bit longer than the others.
So perhaps in relevance to your post…the last oil change I did, I used Quicksilver 10w30 recommended spec for my 2016 115 2.1l merc. I changed the oil for the second time in the season (just with the hours I put on her)…around September.
So getting to the point…I started her just last week on a cold day. About 0 degrees Celsius. Was a noticeable difference in how she sounded for the first minute after start up. Quite rough sounding. Ok after that.
End of last season and into early this year. I started her a few times in the same temperature…but had rock oil 15w40 oil in her. There was no such noticeable rough running.

 

[Chris1956]

Gee, Paul, you may use any oil you like in your marine motors. I am concerned that you would recommend oil not specified by the OEM, to folks asking for sage advice.

FC-W oil is branded by many at prices only slightly above automotive oil, so the savings are not much.

It is obvious that pushing a boat at 5000 RPM is much more taxing on the motor than pushing a car at highway speed, which is 2500RPM or less. it is easy to see in the fuel consumption alone.

If you think your automotive oil is up to it, great. I for one, will use the oil spec'd by the OEM. That is what I would also recommend to anyone that asks.

 

[Lou C]

I have over the years used straight 30 & 40 (Delo 400) and Merc/Quicksilver 25/40. As far as automotive vs marine spec oil I have searched and searched; read many oil analysis reports, and have not been able to come to a conclusion one way or another. However, I will say this, when I had my issue with blown head gaskets & salt water in the oil & a cylinder I was using the Merc 25/40. When I took the engine apart after pickling it what I found was that it was surprisingly free of corrosion. Despite milky oil (changed 3x and drained cooling water each time) nearly no corrosion anywhere. Not in the cyls, not on the valve train etc. Not sure if any oil would have done as well but I have seen engines with similar failures that looked really bad for corrosion.
If you don’t want to use marine spec oil just make sure to use the right viscosity. For inboards that don’t have engine oil coolers I would use nothing less than a 15/40 or 20/50.

 

[paulswagelock]

Gee, Paul, you may use any oil you like in your marine motors. I am concerned that you would recommend oil not specified by the OEM, to folks asking for sage advice.

FC-W oil is branded by many at prices only slightly above automotive oil, so the savings are not much.

It is obvious that pushing a boat at 5000 RPM is much more taxing on the motor than pushing a car at highway speed, which is 2500RPM or less. it is easy to see in the fuel consumption alone.

If you think your automotive oil is up to it, great. I for one, will use the oil spec'd by the OEM. That is what I would also recommend to anyone that asks.

I never recommended an automotive oil, just simply pointed out the false statement about them being inferior. They can be and sometimes are every bit as good as the fc-w oils. In some cases, they are far superior for high pressure wear prevention as almost all FC-W oils are catalyst compatible which limits their concentration of zinc and phosphorus, the two most documented additives for wear prevention. So let’s drop the falsehood that fc-w rated oil is magical, it simply is not.

For a new motor under warranty, I would stick to the viscosity and certifications required by the OEM, but not necessarily their brand.

 

[JimS123]

Yes the manual calls for both 10w-30 and 25w-40 and the service manager said that 25w-40 is a better oil.. but did not mention anything about the temperature. Anyway I do not go out fishing if the weather is below 45F.

I have 4 recent manufacture Mercs, and all 4 manuals have a temp. diagram on the page that details what oil to use. Its quite clear that 10w30 works for everybody, and the 25w40 has a temp. limit.

You have to careful with some service managers. Some have been in the bizness for decades and others just sell you what they have and / or are clueless.

Case in point - 25w40 is the only oil recommended for my older I/O. When I went to my local dealer to buy some 10w30 for my 4 outboards they didn't have any. They decided to minimize inventory and only sell one SKU. He didn't say it was better, just it was good.

That POed me so I went home and went on EBay. Funny thing it was a lot cheaper there and I had it in 3 days.

 

[Lou C]

Agreed I'm sure there is a reason why the 10w/30 is ok for outboards but only 25/40 is recommended for inboards and I'd go with what the manufacturer says on viscosity. I think the old school inboards may shear the oil down more than the outboards do, perhaps due to more friction in the valvetrain, who knows really. We have a little Suzuki DF 2.5 and I use what Zuke recommends in that, 10/40. Yeah I probably could use the same Merc oil in it as well, but if I start using something and don't have problems, I tend to keep using it.

 

[QBhoy]

Agreed I'm sure there is a reason why the 10w/30 is ok for outboards but only 25/40 is recommended for inboards and I'd go with what the manufacturer says on viscosity. I think the old school inboards may shear the oil down more than the outboards do, perhaps due to more friction in the valvetrain, who knows really. We have a little Suzuki DF 2.5 and I use what Zuke recommends in that, 10/40. Yeah I probably could use the same Merc oil in it as well, but if I start using something and don't have problems, I tend to keep using it.

Agree…but there is still the old thing about VP recommending 15w40 on occasion…for the very same engines that merc say 25w40 for. I guess.

 

[Lou C]

Agree…but there is still the old thing about VP recommending 15w40 on occasion…for the very same engines that merc say 25w40 for. I guess.

Really the only difference likely is that the 15w/40 might give you slightly faster starts at low temps, other than that not much difference. Merc says their oil is better because it does not use VI improvers, whereas conventional multi vis oils do, but again not sure how much of an issue this is. I never used the 15w/40 but many people do.

 

[Texasmark]

Did you use a FC-W motor oil or automotive multi-vis? The FC-W oil is made specifically for four cycle outboards, and is supposed to be more robust for the heavier power requirements of the marine engine, versus an auto engine..

The word is that the automotive oil is too wimpy for the high stress use of a marine engine.

Probably its the additives and anti-rust would be the king pin. Course any additive dilutes the lubricity of the oil so they aren't always all that great.