These VW engines are air-cooled and have large clearances when cold. therefore VW’s used different viscosity depending on ambient tempertures. Warm weather I used 20w-50. Cold (below 35) I used 10x-40. Contrary to all wives tails, synthetic is best.
In addition, today’s oils have no ZDDP (Scuff Package). This eats up flat tappet cams. If the SAE rating is SM…it’s not good for flat tappet engines. I use Royal Purple and it’s SAE “SJ”, retaining the scuff package.
The transaxle uses 75w-80 or 75w-90, also based on the climate. I also use a synthetic…Royal Purple gear lube.
The best economical improvement to the way the car runs is to install a Pertonix Ignitor Module and one of their matching coils. It elminates the points/condenser and still looks bone stock.
Today’s fuels are also damaging to the fuel system in these VW powered cars. It’s important to use a top lube like Lucas or Sta-Bil. DON’T LEAVE IT SIT FULL OF FUEL FOR LONG. This stuff will actually disolve some of the fuel pump and carb parts!!! The Sta-Bil helps.