quote:Originally posted by george pence:
George, intersting stuff, being around airplanes, full sythetics are the devils fluid. The Class actions suits against Mobil Oil:
http://www.eaa49.av.org/techart/mobil01.htm
Open the door to the problems with synthetics. Albiet this effects aircraft more severely. They can not disolve the lead deposits (in aircraft fuel) and other deposits which remain in suspention. After discovering these sorts of problems I read about test where they could not get brand new engines to go to 2000 hours with 3000 hour overhaul intervals. With the concentrated sludge it was also damaging propeller systems which pump oil through them.
I am not doubting the high temp and lubrication benifits but the word in avaiation is "PURE" synthetics are as good as water; which is why they are none in aviation oils any more. Very few in automobile oil which contributes to the high price.
Obviously car engines do not have as much lead in the fuel but it's not just lead it cannot disolve. On top of that, the synthetic car oils boast longer oil changes which with it's unability to disolve combustion bi-products, oil changes should be more often.
It is not against any warenty (and amosole is constantly telling people that) because of the Magnuson-Moss act which basically says oils are judged by Viscosity not by brand.
http://www.north-american-lubricants.com/warranties_and_the_magnuson_moss_act.htm
I did a search for articles on oil changes. Found many by Amasol and many others touting long oil change periods, trying to tell people it doesn't void their warenty, trying to dispel comon myths, etc then found many articles about car companies with longer oil change intervals and people finding a lot more sludge in their oil, maintenance guys telling them to go back to the 3000 mile oil change and car companies backing off the use of pure synthetics. The corvette did but I don't know if it still does. I had heard they stopped but don't know.
Modern oils are pretty good and are not going to break down in 3000 miles. If you get 150,000K on pure synthetics, would love to see the info, compresion test, oil change history, would be good info. It's an absolute no no for aircraft.
On the other hand the synthetic blends are still held in high reguard because the blends can disolve the deposits.
The bigest concern with oils is dirty oil. Good fiters, and good oil changes. If a car sits, water is absorbed in the oil and it should be changed at least yearly reguardless of mileage. Dirty oil (especially for older engines with more blow by) acts like sand paper and needs to be clean. I always thought the guys with double oil filters were a good idea.
Gary