The following is a translated version of a quote by a man who worked for Opel, BMW, Mercedes, and Alfa Romeo. He has worked also as an engine builder, and now owns his own shop. He specializes in rebuiling BMW engines. I used Babelfish, and touched the translation up a bit. Excuse the funky English, neither Babelfish, nor I, is a professional translator. The following pertains to our constant "thin" vs "thick" oil debate. In this case it's about thin Long Life oil (0/5W-X) versus thicker oil like 15W-40.
quote:[ August 31, 2003, 03:15 PM: Message edited by: moribundman ]
"I cannot use this oil for my customers (at least not if I do not want to destroy their engines). 80% of all customers have more current engines than model year '94. In these engines the oil pump is no longer located in the sump, but in the "Steuerdeckel" or in the raised position. Since an oil pump has no gaskets, it is never completely tight, and it doesn't have to be tight. When using thicker oil, the oil remains in the pump. The "Sichelräder" [sickle gears] are nicely wet with oil and, due to the thickness of the oil, they are immediately to sucks the oil in. thin oil will flow out of the pump over night, the oil pump gears are nearly oil-free after 24 hours. The suction power of the pump reduces is reduced, In addition, the crankshaft and oil pressure channels emptied themselves and ran dry over night. This does not happen with thicker oil. The further advantages of the heavy oils are also high temperature stability, higher "Druckaufnahme" [pressure reception], even with much cold weather startups, the oil will not be dangerously diluted by fuel, the motor will run quieter (mechanical noises). Even after not running the motor for prolonged times, all parts are still well oiled (with the light oils the cylinder walls are already drying), oil consumption is low, and wear on reciprocating and rotary parts is low, too. Disadvantages of those thicker oils are that they do not release additonal horsepower (by more bearing air), that the cold start cranking speed is slower, that fuel consumption is higher (but savings are equalized by the increased oil consumption of the light oils). Whatever points you make, I take the thick oil, you may take the thin ones. Heavy oils have proven in inummerable cars that they are up to delivering long engine life and high mileage. That the new oils [thin/Long Life oils] are suited to nothing, is reflected in the 29 engines with lubrication problems or complete loss of the motor starting from model year '96 and under 100k km. For me that is not coincidence. ALL have cold tracks in the cylinders (indications of dry sockets with the cold starts), all had busted oil pumps (with scoring throughout), all had Fresspuren [scored marks?] into the connecting rode bearings. 25 of those engines failed due to the scored connecting rod bearings. All of those motors ahd sludge (shows overload of the oil), and I won't use that kind of oil. Why has BMW approved 15W-40 for the V8, m43, m51, m21, m52, m70 , and all M-motors, except the new M3-5? Of course only up to the model year since when only Long Life oil (the name alone makes me want to drop in the dirt!) have been used. And why does a manufacturer such as Motull, which is always at the forefront of racing, produce 4 different 15W-X oils but only one of the viscosities? They must be crazy! Or have they understood?