don't use synthetic oil??

[JustinGray]

man, i want a 747 reall bad.

Actually... the synthetic oil issue did not deal with jets, but piston engines. Continental has a small fleet of air cooled piston engine planes that is uses for short halls. These were the ones that were having problems. I suspect that most any air cooled engine would not like synthetic oil as well, but that is only a guess!

[Jim]

Originally Posted by JustinGray

Actually... the synthetic oil issue did not deal with jets, but piston engines. Continental has a small fleet of air cooled piston engine planes that is uses for short halls.

I'll make sure I don't use synthetic in all the small planes, too.

[Resist]

This should clear things up:

Lubricants made with synthetic base oils are excellent lubricants. The problem is that synthetics are so pure that they are very poor solvents. The automotive industry has developed additive chemistry that works with the synthetic base oil to provide the cleanliness characteristics needed to maintain a clean engine. This means that if you use synthetic-based oil in your car and change it at the proper intervals, your engine should remain relatively clean and offer excellent service and life. Major problems can occur if an owner decides that since the synthetic oil is more expensive, it should last longer and they then extend their oil change intervals significantly. In these cases the oil does not wear out, but can become completely saturated with contaminates like carbon, and then excess deposits can build up.

The problem with the use of synthetics in aircraft is the leaded fuel. Synthetic-base oils are so pure that they do not absorb the lead byproducts of combustion as the mineral base oils do. In addition, because of the necessary limitations on additive chemistry in the piston engine oil specifications, many of the additives used in automotive oils can not be used in aircraft oils.

The problem is not universal. When Shell Oil started to test synthetic piston engine oils back in the 1960s, many engines performed very well on the product. Unfortunately, numerous engines, usually the larger turbocharged opposed engines, started to show signs of increased oil consumption as early as 600 hours. When these engines were disassembled, the pistons looked like someone had taken a gray epoxy and coated the entire piston ring belt and glued the rings into the piston. In addition, the props were full of the same gray sludge, which was found to be lead byproducts of combustion. Shell never marketed a full synthetic oil, however, several companies did and found out the hard way that synthetic oils do not absorb the lead byproducts of combustion.

Aviation piston engine oils are approved against a SAE/Mil specification. The full synthetic oils that were marketed met that specification. When field problems occurred, the oil companies worked with the FAA to solve the problems. However, the FAA did not rule against synthetic oils, the oil companies removed them from the market.

[Billy]

Justin and maybe Jim; sorry to say, but you guys are all wet on this one......(I am a private & commercial rated pilot, & aviation mechanic) The CONTINENTAL referred to here, is not Continental airlines, but Teledyne-Continental Motors, Inc of Mobile, AL. They have manufactured piston aircraft engines since about 1944. It is true that in 2001 they placarded their engines against using Mobil 1 synthetic -----but not because "all their engines seized up". I don't think even 1 seized up. There were some reported problems, but you must understand the avaition industry. To avoid further multi-million $ product liability judgements, they always error toward the side of safety. If there is even a remote question, they will often "pull" a product for further testing.
Actually, I still use full synthetic in my airplane; it reduces friction!! Billy.......

[jimbeemer]

Actually, I specifically use synthetic (Mobil-1 or others) oils in my motorcycles that are air-cooled. It is best because air-cooled engines vary operating temperatures tremendously and the synthetic oil stays in the desired viscosity range much better than petroleum-based oil after the oil has some miles on it. The petroleum based oils more easily shear the hydrocarbon chains which lessens the viscosity as it is used and leads to more engine wear. Until my bikes have a few thousand miles on them I use petroleum based oil (but change it often) to allow more wear and seat the piston rings and other oil-bathed parts. Doing this gives me an engine which uses less oil over the long haul. I hope that this helps.