Re: Engine oil

Posted by Owen_Dyneto On 2008/2/8 9:52:30

Let me digress from the original topic to that of oils for the earlier engines. Despite the terrific advances in motor oil since the early thirties when they were marginally refined crude oil, none of them can turn a slow-revving, long-stroke, babbit bearing engine into a streaking speed demon. In the era when 65% of the nation's roads were unpaved, 45 mph was a challenging and not commonly reached speed and the cars were geared accordingly. Changing your oil frequently, dropping and cleaning the oil pan regularly, and keeping to the speeds for which the car was originally engineered are probably far more important to good engine life than the specific oil type used. Although there maybe something that appeals to logic about using higher viscosity oils (for cushioning effect?) in the older engines with babbit bearings, it is probably a bad idea. Higher viscosity translates into lower flow rates which transfers into less heat transfer and heat is the major enemy of babbit materials. Thus for these early engines I'd recommend sticking to the viscosity recommended by Packard at the time. If the engine is clean internally, I doubt that it makes a difference whether you use detergent or non-detergent, though the engines of the 33-39 seniors had full-flow oil filters and heat exchangers. I'd make an exception for the Twelves and use detergent single viscosity because they have hydraulic valve clearance dampers with very fine tolerances.

When you get to the advent of the 356 engine and those that follow with hydraulic lifters, a detergent oil is much recommended but again you should insure that the engine is clean inside. If the car was recently purchased and you don't know when it was last done, drop the pan and clean it along with the valve lifter galley. Again, driven sensibly at the speeds for which they were engineered, a single viscosity detergent oil should be fine but likewise a multi-viscosity grade should be OK but I'd avoid SAE10W-40 which is probably the poorest of the bunch due to very high levels of viscosity extenders. If your summertime temperatures are in the range that Packard recommended SAE 40 for, then I'd use SAE15W-40 like Rotella T or Delvac because you can benefit from enhanced additive packages that include anti-scuff additives. In any case those are my opinons, feel free to differ.