Synthetic oils are fine. I do want to clarify something though. I have
always promoted good synthetics (the heat rejection issue is BS, we have
tested them; it may have been true in 1980, but in 2003 when we tested it
was proved (to us) to not be an issue). YMMV.

But you have to make sure you match the oil to the engine. When I say that,
I am specifically referring to the bearing clearances, which is also related
to engine life. Modern engines, which "like" synthetics a lot more then the
older ones, have much more accurate and tighter bearing clearances due to
improved assembly line machining. It may open some eyes to hear that NASCAR
engines break the engines in on peanut oil, and race with 0-40 oil, running
10500RPM for 500 miles at a crack. Try to do this with dino oil and the
engine is history real quick. Thin oils move thru the journals quickly,
removing heat. Yes the oil pressure is lower, but oil pressure doesn't
lubricate the journals. Set your bearing clearances to .0005" and run 20-50
oil and you'll have great oil pressure, and tell us how long the engine runs
before it siezes from overheated journals! You won't need to count it in
thousands of miles, simply counting you fingers and toes should suffice. ;-)

Watercooled engines can run "thin" oils easier then aircooled, because
watercooled engines run in a closer temperature range then their aircooled
cousins. More temp range means more clearance range in the engine. A
combination of too much clearance and too thin an oil means BOOM. Running
tight clearances with thick oils means BOOM too, you have to be in the
middle somewhere for everything to be happy.

You are crazy to run straight weight IMO, oils have come a long way in 30
years; and for those that say they do it because the owners manual says so,
the owners manual is how old? ;-)

Factory engines from VW (aircooled) come with 5-30 or so in them last I
checked, and that's what the owners manual says to run too. Aircooled
engines can run cooler with thinner oil, but like I said before too thin and
BOOM.

I can't believe I'm adding to the oil thread, I promised myself I wouldn't
do it LOL.

John
Aircooled.Net Inc.