Path: utzoo!attcan!uunet!bu.edu!att!cbnews!military From: scw@ollie.SEAS.UCLA.EDU (Stephen C. Woods) Newsgroups: sci.military Subject: Re: SR-71 congealed oil Message-ID: <1990Oct24.150459.15391@cbnews.att.com> Date: 24 Oct 90 15:04:59 GMT References: <1990Oct8.220953.7541@cbnews.att.com> <1990Oct10.000645.444@cbnews.att.com> <1990Oct11.051057.29887@cbnews.att.com> <1990Oct15.034029.13416@cbnews.att.com> Sender: military-request@att.att.com Organization: UCLA School Of Engineering & Applied Science Lines: 45 Approved: military@att.att.com From: "Stephen C. Woods" >From: argosy!freeman@decwrl.dec.com (Jay R. Freeman) [...] Mobil 1? > >I have heard of the gas-in-oil trick, somewhere. I think possibly >that special, built-in hardware for this purpose is called an >"oil-dilution system", but I have an uneasy sense that I may >be applying a correct name to the wrong apparatus. Some Cessna C-172 and C-182 modles have this option. It is specificly for cold weather operations. >This flight involved a brand new engine in a brand new plane. The >tendancy at such times is to run the beast on a simple grade of >uncompounded mineral oil, with no fancy additives. I am not sure why. Durring the engine break in period you run 'straight' mineral oil because it has the MOST friction, and LEAST lubricating ability. The idea is to get the rings to wear a bit so that they fit snugly. Typically you rin straight oil until the oil consumption (somewhere in the order of a quart every 3-4 hours of so) stabilizes. After the break-in you can (and usually do) run a multi-grade oil. >Many [...] airplanes used for hire get an oil >change at least every hundred hours of operation, in any case. Uhmmm isn't that every 50 hours (aproximates 3000 miles in a car)? It seems to me that both Lycoming and Continetal specify 50 hours between Oil changes unless (multiple qualifiers...). >Lightplane engines tend to run somewhat hotter than (say) automobile >engines, and when they are run it is typically for several hours at a >time, at a high percentage of peak power. oThis is why it is important to change the oil regularly, oil begins to break down fairly quickly at higher temperatures, also as oil is run through the engine, mechanical shearing breaks down the long chain polymiers that help oil hold its viscosity at higer temps. Shouldn't this discussion be in sci.aviation/rev.aviation? -- ----- Stephen C. Woods; UCLA SEASNET; 2567 BH;LA CA 90024; (213)-825-8614 UUCP: ...!{ibmsupt,hao!cepu}!ollie}!scw Internet:scw@SEAS.UCLA.EDU