Car motor oil in a merc cuisier ?

[sappington]

I am getting ready to change my oil in my searay went to the auto parts store to get marine oil they did not stock it and told me they didnt think they was any differece,any one know the problems with car oil instead of marine oil,the 6 bucks a gal is not a issuse just want to know. thanks rick

 

[sprink56]

Well, at least you didn't ask about a portable generator or about leaving your power cords in the water, that's a start anyway.

Try a search on this and you'll get the answers you seek. Short line is auto oil doesn't protect against corrosion like marine oil does. I am strictly of the opinion that auto oil has no business in a marine engine. Others may disagree, but do your own research and I think you will find that you shouldn't use auto oil in your boat.

+1:thumbsup:

There are corrosion inhibitors in Marine Service Oil that are not present in standard API/SAE Motor Oils. If you find a major brand, I.E. Valvoline, Penzoil, Havoline, etc. that is graded for Marine Service, it will have the required corrosion inhibitors.

 

[Hampton]

Simpson's did it.

Don't use auto oil. Use marine oil meeting Merc Specs. Merc 25-40 Synthetic blend is supposed to be good for all 4-strokes, I think. Now, there's a Merc Pure Synthetic which I also believe is approved for all of them - check you manuals, or ask your dealer to be sure.

 

[jason78]

I agree with the other posts. Go with Mercury/Quicksilver Oil or other suitable Marine oil. You may spend a couple bucks more but it will be worth it.

 

[LTD.330]

Corrosion Inhibitors? One would think a good coating of oil on the inside of the closed system known as an engine would be sufficiently protected. I've been running straight 40W oil.

From Mercruiser's website:

 

[tdappleman]

Use an FC-W rated oil. Brand is up to you but the FC-W rating on an oil means it has gone through additional testing specific to the marine environment. You don't have to run Mercruiser oil - but if you are under warranty I would.

Quote from NMMA page: http://www.nmma.org/certification/programs/oils/fc-w.asp

"Industry leaders in lubrication developed testing criteria for this marine four-stroke oil. These include bench tests for viscosity, corrosion, filter plugging, foaming and aeration. In addition, the oil must successfully pass a 100-hour general performance engine test."

On that page is also the complete list of all FC-W rated oils so you can decide which will work for you.

 

[tobnpr]

Use an FC-W rated oil. Brand is up to you but the FC-W rating on an oil means it has gone through additional testing specific to the marine environment. You don't have to run Mercruiser oil - but if you are under warranty I would.

Quote from NMMA page: http://www.nmma.org/certification/programs/oils/fc-w.asp

"Industry leaders in lubrication developed testing criteria for this marine four-stroke oil. These include bench tests for viscosity, corrosion, filter plugging, foaming and aeration. In addition, the oil must successfully pass a 100-hour general performance engine test."

On that page is also the complete list of all FC-W rated oils so you can decide which will work for you.

The information you're quoting is for 4-stroke OUTBOARDS.

I agree with the above poster. There is no significant difference in the internals of a "marine" engine.
They're nothing more than marinized automotive blocks. Same engines made by GM that are in your car....

My 2005 Crusader manual specifies API Service "SM" which is the newest category introduced at the end of 2004. It also specifically EXCLUDES the use of synthetics.


If Mercruiser's "marine oil" is different somehow (other than the higher price), let's see it.

http://www.aa1car.com/library/api_motor_oil_classifications.htm

 

[jellyfish]

I have been using ROTELLA (diesel engine oil) for several years... Works great!

Walmart sells a 2.5G container for +/-$25.

 

[JV II]

I say go against the advice of the greedy engine manufacturer. Put auto oil in their engine that runs continuously for 3500 to 4000 rpm under heavy load in a harsh environment. Save yourself $20 on each oil change. See what happens and report back here. Thanks.

 

[Alex D]

It is a hotly discssed topics and I am putting my flame suit on. After numerous oil analysis on www.bobistheoilguy.com we pretty much know that Mercruiser oil is a blend of two single viscosity oils, not a multi viscosity oil or a multi viscosity oil with very little viscosity enhancers. reason being that continuous high rpm, high load sitautions quickly break down the enhancers which tehn easily form sludge. In addition we found that the additive packages in MErcruiser oil are not all stronger or better than HDEO oils (diesel engines) or HM (High Milage) oils.
I have for years used a good HDEO 15W-40 diesel engine oil in Mercruiser small blocks or Castrol GTX 20W-50 High Mileage oil in the 8.1s engines.
They have better additive packages and are built for high load, high temp operations. One point to support this is that marine diesel engines use regualr diesel engine oil, no special Mercruiser or marine diesel oil.

 

[Loneranger]

It is a hotly discssed topics and I am putting my flame suit on. After numerous oil analysis on www.bobistheoilguy.com we pretty much know that Mercruiser oil is a blend of two single viscosity oils, not a multi viscosity oil or a multi viscosity oil with very little viscosity enhancers. reason being that continuous high rpm, high load sitautions quickly break down the enhancers which tehn easily form sludge. In addition we found that the additive packages in MErcruiser oil are not all stronger or better than HDEO oils (diesel engines) or HM (High Milage) oils.
I have for years used a good HDEO 15W-40 diesel engine oil in Mercruiser small blocks or Castrol GTX 20W-50 High Mileage oil in the 8.1s engines.
They have better additive packages and are built for high load, high temp operations. One point to support this is that marine diesel engines use regualr diesel engine oil, no special Mercruiser or marine diesel oil.

I wish I had found bob's oil site when I tried to find out about Mercruiser's gear lube. Mercruiser's gear lube does not even state the viscosity on its labeling.

http://clubsearay.com/forum/showthread.php?t=17959

Thanks for the link to the bob oil site.

John

 

[Woody]

I say go against the advise of the greedy engine manufacturer. Put auto oil in their engine that runs continuously for 3500 to 4000 rpm under heavy load in a harsh environment. Save yourself $20 on each oil change. See what happens and report back here. Thanks.

Here is a quote from my Mercruiser engine manual, or use "a good grade straight weight detergent automotive oil per the operating chart below". Can't be that bad if their publications and current website recommend it as well as other oils for use in their engines.

 

[jason78]

Unless you were looking for a better oil, I don't know why one would not just use the recommended Merc oil. The 25W40 is $5/qt at West Marine and most decent oils run $4 at the auto parts store. Unlike most marine products, the merc oil is really not that overpriced. :huh:

 

[midway]

My first boat, 17 foot Seville with 3.0 I ran Kendall GT1 20 50 for 17 years and it worked fine, current boat has had nothing but the Merc oil and filter run in it and all is well. I will probably continue to run the Merc oil, as stated it is not that much different in price, the last I got was in Walmart.

 

[tdappleman]

The information you're quoting is for 4-stroke OUTBOARDS.

I agree with the above poster. There is no significant difference in the internals of a "marine" engine.
They're nothing more than marinized automotive blocks. Same engines made by GM that are in your car....

The Mercruiser chart specifically calls out the FC-W rating. The NMMA page does say 4 stroke outboards but marinized automotive engines are also 4-stroke. These engines live and operate in a different environment than their automotive counterparts. There are differences and while it's always a personal choice on what we end up using - it doesn't mean the FC-W rating shouldn't just be discarded just because GM made the core components. Bottom line is the oil provides an additional level of protection against corrosion and has been tested in a marine environment. Is it better or worth the additional money - maybe not - but I'll continue to use it and if someone asks for my recommendation I'll give them the same advice.

From the Mercruiser web site - an automotive oil is the last choice in their order of recommendations. I wont use the Mercruiser oil because of both price and I don't trust their rating of it being a 25w40 oil when it has been proven it is a blend of oils.

To help obtain optimum engine performance and to provide maximum protection, we strongly recommend the use of the following oils listed in the order of recommendation:

1. MerCruiser / Quicksilver Synthetic Blend, NMMA FC-W rated, 4 cycle oil.
2. MerCruiser / Quicksilver 25W40 NMMA FC-W rated oil.
3. A NMMA FC-W rated oil.
4. MerCruiser / Quicksilver 4-cycle 25W40, non FC-W rated oil.
5. A good grade straight weight detergent automotive oil per the operating chart below.

 

[LTD.330]

Hey Alex,

How does the Castrol 20W-50 compare to straight 40W oil? Is it a better substitute?

Thanks.

 

[HUMPH]

All I can say is I will continue to use the manufacturer's recommended oil. Everyone can use whatever they wish but I will play it safe. These motors are way too expensive to screw around with for about $20 per oil change!

 

[tobnpr]

Clearly no right or wrong answer, and as stated above it's best to adhere to the manufacturer's recommendations.

Crusader obviously does not feel these "additives" are necessary- and they've been producing top-of-the line marine inboards for decades. Not to get in a piss*** contest here, but you'll find a lot more old Crusaders still humming along than Mercruisers...

Here's one fan, granted it's old, but the lessons still apply.
http://www.yachtsurvey.com/GasEngines.htm

"Synthetic engine oils are not recommended for use in Crusader Marine Engines. Synthetics may offer advantages in cold temperature pumpability and high temperature oxidation-resistance. However, synthetic oils have not proven to provide operational or economic benefits over conventional petroleum-based oils in Crusader Marine Engines. Their use does not permit the extension of oil change intervals."

So, believe what you like.

I still say Mercruiser recommends "their" oil- with synthetic at the top of the chart- because they want to you to buy it, not because it's necessary.

 

[Alex D]

Hey Alex,

How does the Castrol 20W-50 compare to straight 40W oil? Is it a better substitute?

Thanks.

I especially chose the GTX High mileage oil! It is thicker than regular 20W-50 and has an extremely stout additive package, stronger than any Mercruiser oil. It is build for corrosion prevention and to fight sludge, while also provifing additives that keep seals and gaskets pliable.

20W50 gie you much more of a viscosity range. You do not want to run striaght 40 weight oil in cold temperatures, It is thinck when cold, while when warmed up it provides no more viscostity barrier than a 25w-50.


I had a slip neighbor who had twin 1070 hp SC 502s in his Skater Cat and he ran straight GTX 20W-50