Oil

[petew]

Mobil 1 Recommended their 0W-40 European Style Oil for Aircooled Flat Tappet Engines. It has enough zinc and phosphorus to be used with flat tappet engines.

That's crazy thin. I'd be pretty worried about low oil pressure on anything but a super tight, new engine. Are you using it? Also, how hot is the climate you're driving it in?

[TJ530]

The first number is the cold thickness. From my understanding of synthetics the oil is a 40 weight oil that when cold thickens to the behavior of a 0 weight oil when cold. You want a thinner oil when starting as it allows for proper flow rates through the engine when starting.
I am currently not using it but will be on my next oil change and on my new engine that's on the way.
Also climate really shouldn't change what oil you use. The oil cooler should be able to keep up with whatever you can throw at it. Using a thinner or thicker oil to get a certain oil temp is a band aid at best IMO.

[Piledriver]

I'm running 0W40 Pennzoil Euro, T4 bottom end with over 500K miles on the main bearings, it has appx 90K on it since I went through it.
Replaced the crank and the factory main bearings checked out in spec still.
I reused the OG rod bearings that came with the $25 crank/rod set from TOS classifieds, crank/bearings measured out as new.

It got new cam bearings, the thrust face was essentially missing, thus the engine made really "funny" noises at idle.(but ran just fine)
I was running 5W30 QS Ultimate Durability, but it was too thin in 100++ temps stuck in traffic commuting, probably 130+ OAT coming off the pavement..

[Chip Birks]

Mobil 1 Recommended their 0W-40 European Style Oil for Aircooled Flat Tappet Engines. It has enough zinc and phosphorus to be used with flat tappet engines.

That's crazy thin. I'd be pretty worried about low oil pressure on anything but a super tight, new engine. Are you using it? Also, how hot is the climate you're driving it in?

I run this stuff. Works well enough for me.