Date: Sun, 25 Jan 1998 00:23:07 GMT From: Ywan Mason <ymasonnopsamsouth.net> Subject: Re: Synthetic oil?
Our shop uses Amsoil Series 2000 Racing oil in the manual gearboxes. My 86 got 225000 hard miles out of it before rebuilding. In the last two weeks, I have rebuilt one box and had to replace another because it was too far gone to rebuild (a complete box was cheaper than the necessary parts to rebuild it). Both of them had gear lube in them, one with 130K miles, the other with 80K miles. Gear lube is not required in a Saab gearbox, the weakness is the bearings, not the gears, there is no need for high pressure lubrication properties of gear lube. Oil will do a much better job lubricating bearing. Gear lubes have high levels of additives which can break down over short intervals of time. Synthetic oil has equal size molecules and much less need for stabilizing additives to break down. we change the oil in our customers cars every 30000 miles. The synthetic gear lube MTL, though I have no experience with it, is rumored to be noticeably stiff after about 10000 miles and requires more frequent changes. Many swear by it, but I see no way to improve on the Amsoil's protection and its longevity greatly out lasts MTL. By no means put regular GL-4 or GL-5 gear lubes in the gear box. They are high in corrosive sulfur and bearing failure will quickly result. With the Amsoil, you will get a slight stiffness on mornings that it is below freezing, but that quickly goes away as the engine warms. Some do not even notice it. The rumor that synthetics defeat the synchros is not founded by my 16 years experience with the gearboxes. My 86 at 225000 had no synchro problems. It now has 240000+ and is still on Amsoil with all its original gears and chains, all I replaced were the bearings, seals and synchros, the last two just because I was there. I am yet to see a gear lube box go over 150K without catastrophic failure both in the bearings, shafts, and gears, even when changed every 7500 miles. A big no no that no engineer I have found can answer is changing a gearbox that has had GL-4 or GL-5 lube in it back to oil. Within 10K, the bearings will fail. My theory is that the gear lube sits up a etching type lubrication that weakens the bearings surfaces when oil leeches the gear lube out. Whatever it is, I can demonstrate from a 25 year old database from our shop that gear lube will kill the boxes. Now MTL seems to be totally different from regular gear lubes, but it still needs more frequent changes than oil and the added cost does not justify any added protection. I do not receive a dime from Amsoil, I just use their products and our shop has for the last 10 years. We have some trannies out there with Amsoil well over 300000 miles. Ywan Mason
 |
 |
 |
 |
 |
