Thank you Alex. I always enjoy learning more about lubricants by reading your posts. If you think it appropriate, perhaps you could address some potential upcoming issues related to engine oils as they pertain to new diesel technology. By this, I mean low-emission diesels... egr-equipped diesels that need the lowest volatility lube oils available... common rail, pump-injector diesels that require special additive packages to withstand the rigors of driving these injectors to their extreme pressures... piston rings that have been moved farther up the piston that need synthetics to reduce crevice coking... We don't have these engines in our boats yet, but one day we will. And, the only lubricants that can handle these tasks will be synthetics. Thanks, -Mel > Greetings Tribologists, > > First off, I'd like to coin a new internet acronym - FOP = For Our > Purposes. In the context of this post that refers to diesel engines in > general and recreational trawler engines specifically. > <snip>

HiHo Luboids, I've had a few public and private follow-up questions to my post and I'd like to take a shot at addressing them. But first, a disclaimer: My opinion about synthetic oil is this - If your application involves extremes of temperature (either low or high) or other special circumstances then you might NEED synthetic oil because mineral oil just won't be up to the task. Otherwise, the use of synthetics is not economically justified. OTOH: There's nothing wrong with synthetics (assuming they meet your engine's specified requirements) and it is, after all, your money! First question - Why do some engine builders such as Detroit Diesel not approve synthetic oil for their engines? I'm not sure that's actually the case. I'm looking at DD's publication "Lubricating Oil Selection Criteria" (available on the Web but I don't remember how to find it again). This pub. says that synthetics are OK for the most part but warns against blindly trusting any extended service interval claims, advising instead that the operator should base such decisions on an oil analysis program. The pub. does say that you should NOT use synthetics that have viscosity index improvers in their 2-stroke engines but I think that's a V.I. improver problem and not a synthetic oil problem. I can't comment on other engine builders without seeing the literature except to say that it would be a natural thing for such an organization to be very conservative about their recommendations and there have been cases of unscrupulous marketing of synthetic products. The logical extension of all that would be for the engine builder to say "Don't use a synthetic oil unless we tell you that specific product is OK. Next question - What about all the changes coming down the pike that essentially make a diesel engine more and more inhospitable for the lubricant? For the most part, the oil companies have found ways of dealing with these issues using more and more advanced mineral oils and additive packages. The real problem in today's marketplace is that the requirements are changing so fast that everyone is forced into a guessing game as to what they will have to do next. [And I mean EVERYONE - fleet operators, engine builders, oil companies, even government regulators.] As an example, the oil companies have had to meet the last couple of API standards by formulating the product BEFORE the standard was finalized. As I said in my earlier post, the day is coming when just about every new heavy truck will have all synthetic lubricants (with the possible exception of grease). I don't think, however, that such a requirement will be due to what I think of as point source problems like EGR or crevice coking. My belief is that the change will be temperature driven - for a number of reasons it's getting harder and harder to get a heavy truck to do all that's demanded of it and still keep the temp down to what we have come to think of as reasonable. Further, it's actually desirable to run a diesel engine much hotter than we do today; basically, the hotter you run the engine (within reason) the more efficient it can be. If I'm right (and I admit to guessing) then most of these issues won't apply to trawlers for twenty or thirty years. Next - What about hot spots such as exhaust valves and turbochargers? Wouldn't synthetic oil be a good idea to cope with those extreme conditions? While it's true that synthetics can handle high temperatures better than mineral oil it doesn't necessarily follow that they are needed just because certain areas of the engine run hotter than the average for the entire unit. Engines are designed such that the oil doesn't linger in these hot spots; indeed the one of the major tasks of motor oil is to provide cooling for those areas. In doing so the oil does heat up somewhat but it certainly stays well below the 140C (284F) 'magic' temperature that I referred to in my previous post. If proper engine management is practiced things like turbocharger coking simply don't happen. OTOH: If the engine is improperly managed you can cook the oil to a temp that even synthetics can't handle. By engine management I'm simply referring to the practice of letting the turbo cool down for a couple of minutes before shutting the engine off; happily, prudent seamanship virtually guarantees that the cool down period will be automatically observed. [Docking, picking up a mooring, or even backing down on the anchor are not done at high throttle settings.] And then - Ester based oil is non-flammable and doesn't break down (thermally) till the temp exceeds 500F; isn't that worthwhile? IMHO, that is a nice property that isn't very valuable in most diesel engine applications. If you're concerned about thermal stability, I think that is addressed above. If we're talking about run-away engines, I personally think that phenomenon is rare enough that I don't worry about it much. If I were to start worrying about it I think it can be addressed better by using an air shut-off mechanism. Finally - Ester based oil has a superior ability to wet steel surfaces and so is better able to protect certain engines during extended lay-up. I won't pretend any expertise on this issue but to my (admittedly uninformed) eye this looks like a solution in search of a problem. I'll keep an open mind though and would be very interested to hear of documented cases of engines having problems relating to mineral oil not sufficiently protecting metal parts during lay-up. I just thought of an anecdote that may pertain to this issue. Many years ago I came into possession of a drag-saw engine (single cylinder, low rpm, low output - intended to operate something like a logger's manual crosscut saw). When I found it, it had been sitting in an unused storage shed for at least 20 years and had not been turned over let alone run in that time. The outside was heavily and deeply rusted but when I got it open the interior was still coated with oil and not a speck of rust was to be found on either steel or cast iron surfaces. The oil itself was pretty nasty which was to be expected since, if I'm reconstructing the time line correctly, it would have been blended with NONE of the additives that we take for granted today. BTW: I never got the thing running due to the fact that I was 10 at the time and had absolutely no clue about what needed to be done. Well, the scroll bar is getting pretty short again so I'd better sign off. Merry Christmas, Alex H.