oil

[godzilla12]

WHAT OIL SHOULD I PUT IN MY ENGINE IT'S 4.3 V6 MERCRUISER? IT IS AN INBOARD MOTOR AND I NEED TO KNOW WHAT WEIGHT OIL?

 

[rabidfish]

Re: oil

Mercruiser make great oil for Mercruiser sterndrive engines. It's labeled 25-40

 

[DJ]

Re: oil

Mercruiser make great oil for Mercruiser sterndrive engines. It's labeled 25-40<br />

Ditto.<br /><br />For as little as that engine is used and as few times you need to service the oil, use the OEM stuff.

 

[LubeDude]

Re: oil

Originally posted by DJ:<br />

Mercruiser make great oil for Mercruiser sterndrive engines. It's labeled 25-40<br />

Ditto.<br />

This is not bad advice, and the Mercruiser oil is a fine oil. This is one of three engine oils that actually meet the new F-WC NMMA designation for marine use. Siera makes the othe two. A 10W-30 and a 25W-40.<br /><br />However, I have absolutly no doubt that any Heavy Duty Diesel oil will pass this test with flying colors, so I believe that any Diesel 15W-40 oil will do the job with less expense. Dello or Rotella would be my choice. My son has run this oil in his 4.3 four 5 years with great results and he runs it hard.

 

[Don S]

Re: oil

Oh Lawd, here we go again.............<br /><br />One More time, with feeling.

 

[TheOilDoc]

Re: oil

By LubeDude:<br /><br />However, I have absolutly no doubt that any Heavy Duty Diesel oil will pass this test with flying colors, so I believe that any Diesel 15W-40 oil will do the job with less expense. Dello or Rotella would be my choice.

I strongly disagree.<br /><br />First, 15W-40 is not a specified viscosity for that engine.<br /><br />Next, those oils will contain polymer enhanced multi-grade viscometric property improvers.<br /><br />These are things that give the oil its multi-viscosity properties, but make the oil more susceptible to shear stress breakdown under the harsh marine environments of heavy loads, extended idles, and fuel dilution. <br /><br />Also, those oils will contain up to 50% more ash. High ash content can cause unnecessary carbon build up in some of the cooler running Mercruisers, especially during idling.<br /><br />Finally, aside from the fact Mercruiser does not recommend those oils, even the oil manufacturers themselves do not recommend them for marine use. <br /><br />Both Delo and Rotella offer marine oils. Delo specifically recommends its Delo 100 straight-grades for marine engines. Rotella also specifically recommends its straight-grades for marine use. Even Mobil manufactures Mobilgard for marine applications. These oils will have different additives beneficial to the marine environment and they will be virtually absent of viscosity improvers that break down under marine-use stress. I fail to see why using their automotive oils would be better. And these oil makers apparently agree.<br /><br />Of course automotive oils work. But in my professional opinion they do not work as well as those oils made specifically for marine applications.<br /><br />You're right member Don S. We’ve discussed this in more detail before.

 

[LubeDude]

Re: oil

I still say they would meet the F-WC rating.<br /><br />The percentage of Ash in engine oils runs anywhere from .75 to as much as 1.7 in conventional oils. Sure less is better, but we are not talking oil burning here unless the engine is worn out. Dello comes in at 1.0% ash content which is decent.<br /><br />Diesel oils are typically quite shear resistant and also resist foaming and oxidation at high engine operating temperatures (which have more to do with load and rpm than the temperature of the coolant). So in general, HDEOs are a good choice for marine applications. Note that 4-stroke Mercruiser oil carries a diesel certification. Thus, they are likely using a diesel additive package that provides that certification.

 

[TheOilDoc]

Re: oil

Sure less is better...Dello comes in at 1.0% ash content which is decent.

No, the Delo 400 15W-40 diesel oil comes in at 1.41%. That's almost double that of their marine oil.<br /><br /><br />

we are not talking oil burning here unless the engine is worn out.

An engine does not have to be "worn out" or "burning" oil to form carbon and other deposites.<br /><br /><br />

Diesel oils are typically quite shear resistant

Not as shear resistant as marine oils, particularly those recommended by Delo.<br /><br /><br />

HDEOs are a good choice for marine applications.

But due to viscosity improvers and the lack of certain additives, not the best choice.<br /><br /><br />

Note that 4-stroke Mercruiser oil carries a diesel certification.

That should be no surprise as Mercruiser has diesel engines. It wouldn't make sense for them to produce an oil that didn't meet the specifications of their own engines.<br /><br /><br />

Thus, they are likely using a diesel additive package that provides that certification.

It wouldn't be an automotive diesel additive package. It would be a marine diesel additive package, along with other additives necessary to pass the NMMA testing.<br /><br />Again, I fail to see a reason to use an automotive oil when there are marine oils specifically made for marine-use applications.