Date: 01 May 2000 00:05:55 GMT
From: magic2626nopsamcom (Magic2626)
Subject: Re: OIL   synthetic or fossil??

I have used Mobil 1 for 7 years in many cars... some now have 300,000 miles plus and still run like when we had 30,000 miles on them. Oil consumption is minimal or zero, performance and fuel economy are excellent. >>>Tom and Ray, Click and Clack, discussed the synthetics this weekend. Their experience is that the viscosity of the synthetics is often overrated. When a synthetic says its range is 5-40 it is more likely to be 5 period.<<<< I find this hard to believe since the European rating system ACEA looks specifically at high performance engines or extended drain intervals when they rate an oil ACEA A3-98... oils that meet the rating include synthetics like 0W-40 and 5W-40. One of the test is kinematic viscosity at high temperatures to simulate sustained high horsepower and high oil temperatures. These tests are for oils used in 300 hp + cars that see sustained high speed use on the Autobahn. I can't imagine they'd survive continous operation above 140 mph if synthetic oil was truly a '5W' and not a '40' at temperature. > It is interesting to note that synthetics are not FAA approved.< That is true, Mobil's aviation synthetic oil lost FAA approval and was withdrawn from the market for leaded gasoline piston engines for aviation use... the Mobil 100% synthetic had problems controlling lead deposits on valve stems in certain Lycoming and Continental engines. Bear in mind that these are designs from the 1930's , and valve stems seem to cause a problem in these engines even with FAA approved oils. Mineral oil basestocks can have better solvency performance for certain deposit control issues like lead in aviation piston engines........ and in emission control diesel engines after 1998, in big rigs. That was why the CH-4 rating and the ACEA E5-99 ratings were created.

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