Sae 40w motor oil? Options

[Ben and Ralph]

So the VW shop that rebuilt my engine had always recommended I use straight 40 weight motor oil. I took their word for it and have used it ever since my car has been running. Now I see that no one here on the world uses it! Have I been using the wrong motor oil? Should I switch? I live in Southern California so temps hit 100+ sometimes, and this is my daily driver.

[Cap'n Krusty]

Back in the 60s, Porsche used to caution against multi-grade motor oils. By the mid 1970s the technology had changed and 20w50 became the oil of choice for 914s, at least in places like So Cal and other areas with a moderate to hot climate. That would include most of the US during the summer months. I would NEVER use a 50 wt. motor oil in a 914 unless it had a terrible low oil pressure problem, and then only until I could get it to a shop for repairs to correct the problem. Pretty much the same for 40 wt. The engine is still cold on startup, and that's where the "20" is important. The thin oil moves well through the engine when its cold, than the multi-viscosity additives kick in and increase the effective viscosity, providing the lubrication the engine needs when its hot. Really modern engines are designed to use even thinner oils, and current 911s call for 0w20 motor oil (many knowledgeable techs prefer 5w20). The tolerances and clearances are MUCH tighter and a thinner oil is required to flow properly.

Whatever brand you choose, be sure to get one with enough zinc to protect the flat tappet lifters and the camshaft.

The Cap'n