Alex, thanks for all your lubrication posts -- very valuable. In your recent post, you mentioned -- "For any given bearing there is a preferred lubricant viscosity. That preference is determined according to speed and bearing diameter. When that bearing is installed in an engine the designer knows what temperature the oil will get to in operation and he specifies a viscosity accordingly. I am wondering if Bob Smith's recommendation to use 40W and "not" 10W40 is based on his knowledge and engine designs prior to the advances in polymer and anti-oxidant technology in the new multi viscosity oils. I have an American Diesel and have found no unusual variation or decrease in oil pressure using 10W40. Bob is a recognized expert in Lehman and American diesel engines and his recommendations are difficult to ignore. I have a friend who was a geologist for many years in Alaska and has many years of experience running diesel engines in marine and field equipment. He believes that multi viscosity oil is superior to single weight oil. He also has an old Lehman in his trawler and has been using Mobil Delvac 1 synthetic and a bypass filter on it for the past 6 years. Also, your comment "...I would think that a pre-luber would give the greatest benefit on a genset. It seems to me that a genset is more likely to be loaded immediately at start-up and is more likely to be shut down without being properly cooled down." Short of installing a pre-lube system, what do you think about using synthetic oil. I have a Kohler 4KW genset that takes just 2 quarts of oil. In an attempt to compensate for the large variations in loading, I have been using Mobil 1 synthetic in it. I change oil every 200 hrs. The genset (Yanmar 2GMF engine) doesn't burn any oil and I have not experienced any problems whatsoever. Thanks, Al Pacific Trawler 37 "Pleasant Moment" Palm Coast, Florida

----- Original Message ----- From: "Dr. Al Miller" <almiller@n-jcenter.com> > > I am wondering if Bob Smith's recommendation to use 40W and "not" 10W40 Look at this post by Garrett Lambert: http://lists.samurai.com/pipermail/trawler-world-list/2002-June/047728.html What Bob says is not "Don't use 15w40". What he says, in effect is "Straight 40 weight works so why change?". I agree with that sentiment entirely but, as I have pointed out there sometimes are logistic reasons to change. Having heard Bob's reasoning I now see no barrier to switching if such a move is warranted for other reasons. > > Short of installing a pre-lube system, what do you think about using > synthetic oil. I have a Kohler 4KW genset The reason I said that a pre-luber could be more beneficial on a genset than on a motive engine has to do with their respective modes of operation. The main engine is typically started at an idle or near idle and is run quite gently for a significant period of time due to "no-wake" restrictions and courtesies in and around marinas and anchorages. Likewise, prior to main engine shut-down we've typically been running for anywhere from 5 to 30 minutes at near idle speed which is plenty of time for the turbocharger to cool down. OTOH: Genset engines are expected to come up to operating speed immediately and, depending on circumstances they could be asked to come up to speed under a significant load as well. When it comes time for shut-down there is no de-facto buffer like a no-wake zone to force a proper shut-down sequence. I think that a pre/post-luber system can act as a substitute for proper procedures in this application. Just so I don't get accused of trying to scare people off let me emphasize that this is a useful tool but it is NOT a necessity. Synthetic oils are more resistant to turbocharger coking than mineral based oils and they may get to the bearings slightly more quickly at start up compared to mineral based multi-grade oil. It is up to the individual to decide whether the advantages outweigh the extra expense. Pragmatically yours, Alex