Car oil suitable for Mercruiser engines?

Z

zeehond_nl

Member
Sep 22, 2010
102
The Netherlands
Boat Info
2004
Engines
Mercruiser 5.0 MPI with Bravo III drive
Hello there,

Is it possible to make use of car oil for your engine of mercruiser?

The reason for my question is that i can buy "cheap" caroil (for example the a 10w/40 full syn made by shell). I want to use that for my soon to buy Sea ray 240 or 270 boat. I have been told that mercruiser uses 25w/40......but that is not for sale in a gasstation :)

So...what to you think....leave that at the gasstation and buy the real 25w/40 stuff or ......????

Thanks for the answers!

Greetings from Holland

Marco
 
The answer to this question has been beat to death here numerous times. You will get just as many different opinions. I have a 2001 Sea Ray 270DA with a single 7.4 Mercruiser that has run its whole life on Rotella 15W-40 diesel engine oil. I have a 1986 Glassmaster 21 Regency with a 5.7 Mercruiser that has run its whole life on Havoline 20W-50. I have a 1966 Glassmaster 17 footer with a 2.5 Mercruiser that ran the first 25 years of its life on Havoline 30W (what Mercruiser recommended back then) and the remaining 20 years it has run on Havoline 20W-50. None of the engines use any oil and I have never had an internal engine problem.

There MAY be a very good reason why Mercruiser recommends THEIR 25W-40, but IMO it is because nobody else sells it ($$$).
 
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I had always used Pennzoil 10w30. But in my last boat, the replacement engine warranty called for the 25W40. That seems awful thick to me, but I guess it does not break down as much under the continuous load? It seems funny that cars are going to lighter weights like 5w20 and boats are going the other way?
 
One question to ask yourself before you start using Automotive oil to save $10 a year on an oil change is; are automotive oils Marine FC-W rated?

If you don't like Mercury oil for some reason, there are plenty of other oils that meet the marine standard for corrosion resistance, areation, etc. I don't mean to sound harsh but I just don't see the sense in using the "cheap" oil in these boats when the savings are almost nothing for something for what is a once a year occurance for most. 4 quarts of 25W40 Quicksilver is about $25 at West Marine in the US. How much money will you save by using the cheap auto oil? I see you are in the Netherlands but I still can't imangine that much of a difference.

Here is more information on FC-W oils- http://www.nmma.org/certification/certification/oil/fc-w.aspx
 
I'm running Amsoil 10w40 Marine in mine and like being able to run a good full synthetic oil in there. I also use the Amsoil Ea filters and get good consistent oil pressure on both engines. If you are planning to get a newer boat or one under warranty I would recommend going with the manufacturers oil and make sure you have receipts/records until you are out of warranty. I repowered mine this winter and the company said 5w30, 10w40 or 20w40 as the recommended oil. The automotive versions of these engines are all running 5w30 but I feel better having the thicker oil in there at the higher RPMs and bigger loads the boats usually see. The FC-W rated oils handle moisture better than the automotive counterparts - although if you change your oil fairly often then moisture should not be an issue as long as the engines are run often.

Amsoil 10w40 link - http://www.amsoil.com/storefront/wcf.aspx
 
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I'm using Amsoil marine oil in the boat and 2 Sea Doo RXTs. Works for me. I wouldn't put automotive oil in the boat or SeaDoo's but I'm not going to blindly stick to the manufacturer's overpriced brand either.
 
I use 15W-50 Mobil 1 oil in my 1994 7.4 Litre engine. Someone mentioned that auto engines are using lighter weight oil now, I think it is because they build those engines with tighter clearances versus most older big block motors that weren't made with tight clearances. PLUS, boat motors put a lot more load on the crankshaft than a car engine. The heavier oil tends not to break down. One reason I switched to the full synthetic. But I'm sure this has been discussed a million times on here. Just my 2 cents worth........jd
 
I used pancake syrup in my 7.4 this season with good results.
 
zeehond_nl said:
Hello there,

Is it possible to make use of car oil for your engine of mercruiser?

The reason for my question is that i can buy "cheap" caroil (for example the a 10w/40 full syn made by shell). I want to use that for my soon to buy Sea ray 240 or 270 boat. I have been told that mercruiser uses 25w/40......but that is not for sale in a gasstation :)

So...what to you think....leave that at the gasstation and buy the real 25w/40 stuff or ......????

Thanks for the answers!

Greetings from Holland

Marco
Click to expand...


Marco

Curious if your more or less undecided on what oil to use now?

Lubrication in general (certainly not exclusively to the marine industry) is a subject of great confusion, controversy, and many wives tales PLUS many OEM's, lubrication manufacturers, and those marketing the various products purposely add to the confusion by doing everything from making up grand claims of superiority to actually lobbying the US government to change it's spec or requirements as to what can be called a synthetic etc.

I would recommend a thorough internet search to accompany your findings here, and be sure to check closely into the actual brand you intend on using as not everyone's oils are the same if they do meet the same loose specs.

Hope that helps.

PS how is the boating in your area?
 
themikehyde said:
I had always used Pennzoil 10w30. But in my last boat, the replacement engine warranty called for the 25W40. That seems awful thick to me, but I guess it does not break down as much under the continuous load? It seems funny that cars are going to lighter weights like 5w20 and boats are going the other way?
Click to expand...

The car manufacturers do this to gain gas mileage to sell cars as everyone is on the mpg wagon. They do not give a crap what happens to the engine once out of warranty. Check out some of the new car user forums for brand new vehicles with very black exhaust and burning oil
 
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