My first choice is Castrol 20W-50 . . . Second choice is Havoline 20W-50 . . . Third choice is Castrol or Havoline HD30 . . . but not when the temps drop into the teens or lower. I know for a fact that at 5 degrees HD30 is about as thick as the goo that was in a Stretch Armstrong.
The most important thing about oil in an air-cooled VW isn't necessarily what brand or grade it is . . . changing it often is. Since these engines don’t have a filter, the only way to keep it clean is change it often.
I may be way off base, but here’s the reason I wouldn’t ever use synthetic oil in an air-cooled engine -- In most modern engines, oil is used for lubrication. It's just to keep metal from rubbing on metal and stuff from wearing out. Nothing more, nothing less. Hands down, synthetics can do a better job of lubricating moving parts. They are designed to not break down under the stress of extreme heat. They don’t absorb heat quite as quickly as dino oils. You always hear these older VW engines referred to as "air-cooled" but in reality, they are both air-cooled and liquid cooled. The oil not only has to keep things lubricated, it has to readily absorb heat and then dissipate it through the radiator. I haven't lost my mind. Your "air-cooled” engine has a radiator. It's better known as an oil cooler. The original flat four prototype engines didn't have an oil cooler and had a nasty habit of breaking crankshafts. When the oil cooler was added, this problem was virtually eliminated. So, synthetics might do a better job of lubricating, but they don't do quite as good of job disipating internal engine heat. That, coupled with the high price of synthetics and the need to change it often, dino oils just make more sense.
I've never had a problem with Castrol or Havoline, regardless of the grede . . . except when I ran HD30 when it was 5 degrees. :wink:
