Motor Oil - Synthetic or Not? 

    Motor oil development has changed the way engine parts such as crankshafts and camshafts are machined. New Porsches require synthetic oil. What is the significance of that? Engines with close tolerances require a thin lubricant. Synthetic oil provides superior protection to moving parts, better flow properties when cold, and more resistance to high-temperature breakdown as compared to conventional oil of the same weight.

While synthetic engine oil provides excellent lubricating properties, I hear a lot of owners of older Porsches say: "Synthetics make my Porsche leak".

When building a new engine for your Porsche, deciding what oil to run will be one major consideration affecting how tight to make the tolerances. In the case of 944 owners, along with oil choice you can choose to double drill the rod journals or to change their radii to take advantage of newer oils that didn’t exist when the engine was originally designed. 

There are many brands and grades of synthetic oil on the market today. All have been extensively tested in the laboratory and in the racing world. Amsoil, Mobil 1, Lubromoly, Motul, and Red Line are some choices. Different weights provide protection under different conditions. 0w40, 5w40, 15w50 and many more are available.

At Autobahn, we weigh several factors before considering what oil you should run. Of these factors, one of the most important is viscosity.

Viscosity is a fluid’s load-carrying capacity and ability to flow at various temperatures and loads. However, a proper balance must be achieved for the oil to work well in real world conditions. For example, a race engine may be able to run much higher viscosity oil with a narrower operating range since it will rarely experience a cold winter start. A street engine built to the same tolerances will need oil that provides high temperature/high load protection and also be able to flow easily when cold. Too low a viscosity will flow well but allow metal-to-metal contact when hot. On the other hand, too high a viscosity may raise engine temperatures, reduce efficiency, and cause hard starting in cold weather.

The next big question from late model Porsche owners is: "Why are my oil change intervals so long?" Synthetics do not break down like conventional oils; the main factor to consider for oil change interval is not oil break down, but rather dirt or "products of combustion" in your oil. Oil filtration is the limiting factor.

So, should you use synthetics? In general, yes. The age of your car and your style of driving sets the tone for the lubricants your Porsche needs.

I hope you find this information useful and use this knowledge to help keep your engine and transmission running smoothly for years to come. Not all 911s leak oil.  In reality, the leaks were already present and have only appeared due to the synthetic's excellent flow properties.  Choosing to repair these leaks is easily jusitified when one considers the reduction in engine wear that synthetics provide.