Dear Tom and Ray:

My question is about oil. I already know that the numbers (such as 10W30)
are a measure of the oil's viscosity at low and high temperatures. I just
inherited a 1970 VW Bug. It is of great sentimental value to me and I'd
like to keep it for a long time. My brother says the best thing for this
Bug is a 20W50 synthetic oil. The VW manual says to use a 30 weight oil.
How can I determine if a different type of oil would be more appropriate? -
- Chip

TOM: Well, the general rule is that you use whatever weight oil the
manufacturer recommends. But we're going to make an exception in your case,
Chip.

RAY: Back then, most other manufacturers used to call for a 10W30 or 10W40
oil, which behaved like a 10 weight when it was cold, and a 30 or 40 weight
when it was hot. The reason was that you wanted a lighter oil when the
engine was cold so it was easier to start, and a heavier oil when the
engine was hot for increased protection.

TOM: Volkswagen called for a single viscosity 30 weight oil because they
didn't want an oil that was thinner under ANY circumstances. These engines
were air cooled and were notorious for overheating. And a thinner oil just
wouldn't protect them.

RAY: And to make matters worse, they didn't have temperature gauges. So you
wouldn't know your engine was melting until it sucked a valve or you saw
flames in your rear-view mirror.

TOM: In this case, I would say 20W50 would be an excellent idea. The 50
weight protection will help keep your engine from melting, and the 20
weight viscosity (which is thinner than the original 30 weight) will help
you start the car in colder weather.

RAY: And if you want to use synthetic oil, go ahead. I'm sure it's fine. VW
didn't recommend it back in 1970 because there WASN'T any synthetic oil on
the market back then. In fact, this car came out several years before the
disco craze, so synthetic leisure suits hadn't even hit the big time yet.