Classic Porsches with air cooled engines should use a motor oil with a high Zinc content. Specifically, ZDDP, or Zinc dialkyldithiophosphates, are motor oil additives designed to reduce wear on internal components. For motors without catalytic converters, a motor oil with high ZDDP is recommended. For those with catalytic converters, a hich ZDDP content can lower efficiency of the converter.
Which oil to use?
For the 914 with the four cylinder engine, or the six cylinder 911 engine, here are some good choices:
- Brad Penn 20w50 is a trusted oil that is high in zinc phosphates.
- Joe Gibbs Racing DRIVEN DT50 02806 Full-Synthetic 15w50 Aircooled Engine Oil
- Lucas oil 20 50 High Zinc for Hot rods
- Delo LE-400 15W-40, often available at walmart is also a good choice, at a good price
20w50 is a good choice, especially in warmer climates.
Originally, the 914 was recommended to use 30W single grade motor oil. The use of multi-grade is now preferred, even by Porsche.