Discussion of synthetic oil in 5-speeds

Saab specifically says not to mix the synthetic with natural oil (the procedure below describes how to flush the old oil out).  Note that it is pretty much impossible to get all the oil out of transmissions that are not equipped with a drain plug (pre-94), so you should consider whether you want to try it on the earlier models.  Note also that the synthetic was developed specifically for a transmission upgrade (to quote Service Advisory # 471-1742, dated June 1997: "A new gearbox oil has been introduced due to design changes and reduced face area (sic - I think that should be "surface"), which puts higher demands on an oil's temperature resistance".  Note further that the Saab procedure refers to draining the oil via the drain plug and checking the full level at the end of the procedure by means of the fill level plug, and both of these are on the later model transmissions only; this tends to imply that the synthetic is only intended for 94 and later transmissions.  One more note:  I have read or heard somewhere (can't recall a source to quote) that says you should end up with less than 10% 10W30 in the Saab synthetic addition.  I think this is near impossible to achieve with the pre-94 transmissions (no drain plug).

I prefer to stick with what I know works, as I am not convinced that the synthetic provides any particular advantages.  Some people say the shift action is improved with synthetic, but others say they did not notice much, if any, improvement.  

If you do decide to make the switch on an earlier transmission,  Rick D. has some tips to get as much of the old oil out as possible: "You can get a little more oil out if you park the car so that it slopes to the left (driver's side). I also added a thinner copper tube extension to the 3/8 I.D. hose that came with the pump. This helped get the opening a little deeper. Finally, put it in neutral."  I have found that I can only get a little more than a quart of the oil out , at best.

Service Advisory 471-1742, distilled (it was in a format that I could not effectively import):

Drain the oil from the gearbox by means of the drain plug.

Re-install the drain plug, then fill with 1 liter (1.05 qts.) of the new synthetic oil, PN 87 48 733.

Run the car so that the oil flows thoroughly through the system.

• Not that this is only about half full, and note that they say 'run the car'.  This could mean "drive the car" or it could mean "run the car with the transmission in neutral and the clutch engaged"; I would tend to think that the latter would be sufficient to mix the oil and in any case, I don't think I would drive the car for more than a couple of  blocks with only a quart of fluid in it.

Drain the oil from the gearbox and discard the drained oil. 

Fill the gearbox to the correct level (1.8 liters/1.9 qts.) with the new synthetic oil  (PN 87 48 733) and check the level (and here they refer to the level check plug).

Affix the labels from the oil container to the radiator cross member and to the gearbox oil text in the owner's manual Technical Data section to indicate that  the Saab synthetic oil has been installed.