Bryan,
SAE 20 or 30 are monograde oils (20 weight, 30 weight, etc.). They are for warm weather only applications. The 5W, 10W, 20W are referring to muti-viscosity (cold temperature) capabilities, not the actual viscosity. As it shows in the manual a 5W-30 oil will flow sufficiently at -30 degrees and still hold its viscosity (30) at 90 degrees. The actual kinematic viscosity is classified at 100 degrees C.
Depending on how cold it gets where you are, a 5W or 10W-30 or even a 10W-40 would be sufficient. A 20W-50 might be a little too high of viscosity unless most of your driving is during very hot summer days. As Tiny said, just make sure that the oil you use has sufficient ZDDP levels. Most newer oils have reduced zinc and phosphate which are needed for proper lubrication of the older engines.
Last edited by magfarm51; 08/13/2009 8:35 PM.
