Recent changes in the formulation of most commercially available
motor oils having raised concerns about continued use of those oils in
356 engines, the club invited Charles Navarro, president of LN
Engineering LLC, to come to one of our winter meetings and tell us what
356 owners need to know about engine lubrication.
Charles's presentation went into considerable depth, and we present only the highlights here. His full statement on the subject can be found of his company's Web site at http://www.lnengineering.com--where you will also find the oils he recommends offered for sale.
The problem.. The concentrations of antiwear
additives (primarily compounds of zinc and phosphorus) in motor oils
have been reduced in recent years. This has happened because car
manufacturers want to increase the interval between oil changes for new
cars and to extend the lifetime of catalytic converters (which they must
warranty for 8 years). Newer cars can do without the antiwear
additives because their engines use lower-tension valve springs that
reduce the need for boundary lubrication on the camshaft and cam
followers. But Porsche 356 (and air-cooled 911) engines have very
stiff valve springs and need the additives. Use of the newer oils
with API (American Petroleum Institute) ratings of SM or CJ-4 in these
cars can lead to camshaft failures and expensive engine rebuilds.
The solution. Use a motor oil that contains the concentration of antiwear additives required by an air-cooled Porsche engine. Charles recommends (and sells) two oils for the 356: Brad-Penn Penn-Grade 1 Racing 20w50 Motor Oil and Swepco 306 15w40. An alternative is to supplement a regular oil with a product like General Motors EOS or STP 4-Cylinder Oil Treatment, but Charles cautions that getting good results with supplements can be difficult because both the amount of supplement required and the quality of the outcome will vary depending on what kind of oil you start with.
General recommendations. Along with using the right oil, Charles recommends that 356 owners: