Charles Navarro's Motor Oil Tech Session, January 19, 2008

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 Navarro with the first slide of his PowerPoint presentation.

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 you will also find the oils he recommends offered for sale.

API rating on an oil bottle label. CJ-4 and SM: not for a 356!

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:

  1. Change the motor oil no more often than once a year, or every 2500-3000 miles for a 356 (5000-6000 for a 911), whichever comes first.  Change the oil just before you put the car away for the winter, because letting an engine sit with dirty oil in it can cause trouble.
  2. Consider adding full-flow oil filtration to their 356 engines.
  3. Not use cheap gasoline.  The off-brand fuels can have a higher sulfur content and contain water.
  4. Use a fuel stabilizer if the gas in the tank will not be used within one month.
  5. Change the oil after any use of a fuel system cleaner, so that any residue from the cleaner will be removed with the old oil.