Oil in marine diesels

[Steve Dion]

Here is another article on oil in a marine engine.

It takes a slightly differnt point of view on why you need to run some of these small diesel engines at higher RPM's. While many would like you to believe that you are saving your engine at lower RPM's this article reinforces Yanmars position on running your engine on traditional oils and higher RPM's.

http://coxengineering.web.officelive.com/oil.aspx

 

[kloudie1]

Good article, Steve. Thanks
Shell Rotella T here in the US ..

 

[RichH]

Good article, thanks

The time honored precept of running stationery or diesel 'prime movers' (generators, compressors, etc. ... and not 'lugging' the engine - slow speed, high combustion pressure) in industrial applications to obtain the longest service life of such engines is simply to run them at ~75% of max rated rpm, and change the oil at near the recommended changeout interval.

Such 'steady state' operation (also targeted by many long haul diesel trucks) still seems to be the 'key' for 'long life in service'.

 

[Gunni]

Disturbing. This source says the replacement for Yanmar-spec'ed CD-4 is CF-4. Rotella T 15W-40 is rated CJ-4. Yet says it meets CF-4 spec.

 

[silverbeard]

Disturbing. This source says the replacement for Yanmar-spec'ed CD-4 is CF-4. Rotella T 15W-40 is rated CJ-4. Yet says it meets CF-4 spec.

Oils have to meet previous specs. So an oil, rated CJ-4, which is a newer spec, will still work in a motor calling for CF-4. But one should not use a CF-4 in a motor which calls for CJ-4.

 

[rardiH36]

Steve:

Thanks for posting this link. Reading the many postings on this forum over the last five years about the undesirability of running our small diesels at too low rpm/load -- and/or at steady rpm for too long a period -- I do try to avoid the practice.

But I had no idea that the current hi-tech engine oils can actually cause damage to our older engines.

The info in the link does reinforce/vindicate my life-long tendency for my autos (and now my boat) not to spring extra bucks for supposedly "better" synthetic or otherwise latest generation additive oils. Instead much more important not to stretch out the recommended oil changes by too much. Five/Six cars in my life -- most purchased new and kept to 100k+. Never a mechanical engine failure.

Oh, and I have always changed my filters only every other oil change. Not because I'm really that cheap (frugal yes I'll admit to), but because I always felt that after the engine's break-in period, a filter was good for more than just one oil change. And frankly its a lot easier/faster to do a DIY oil change without also doing the filter. Here's something interesting that most small/older Yanmar owners probably haven't noticed. My official Yanmar 2QM20 manual specifies an oil change every 100 hours. The oil filter -- replace every 300 hours.

Finally vindication for my every other oil change practice!

rardi

 

[Steve Dion]

Personally I think you will NOT go wrong with the Chevron or Shell product. The main thing I took from this article was the fact that those who think that running their engines at low RPM's is saving their engine, when it is actually detrimental to it's longevity.

Use it as designed (don't assume that you know more than the engine designers).

It has always been my contention that a marine engine lives a much easier life than most automobile/truck engines. Stop and go in temperatures that can range from 40 below to 120 above zero and stop and go with untold hours of idleing. It does not get much worse. The worse thing we have to contend with is the possiblity of a blockage in the raw water intake and the salt water (for some of us).

MOST of the time our engines always have nice cool cooling water to maintain a relatively constant environment.

 

[Gunni]

Oils have to meet previous specs. So an oil, rated CJ-4, which is a newer spec, will still work in a motor calling for CF-4. But one should not use a CF-4 in a motor which calls for CJ-4.

Yes, now I understand. Link states 4 rating is per Total Base Number (TBN). Older, slower diesels rate 4 TBN; newer turbo motors may rate 12 TBN.

So the TBN rating is keyed to the engine / drive install. Running speed, and running temps inform choice of oil. Slower/cooler -4, Faster/hotter -12.

May have learned something today!