Synthetic or Dino?

[olegoat345]

I prefer AMSOIL MC oil. Whatever you use, make sure it's MC oil. MC oil has a additive that will protect your clutch & keep it from slipping. Regular automobile / car & truck oils does not & could screw up your clutch. Serious $$$$$

[F6Dave]

I prefer AMSOIL MC oil. Whatever you use, make sure it's MC oil. MC oil has a additive that will protect your clutch & keep it from slipping. Regular automobile / car & truck oils does not & could screw up your clutch. Serious $$$$$

Some MC oils actually lack an additive that could cause problems with wet clutches. Lower viscosity (<30) oils with an 'energy conserving' label on the bottle usually contain 'moly' (molybdenum disulfide) to reduce friction. Larger quantities of this additive have been known to cause clutch slippage in some MC engines, so MC specific oils usually contain less or none at all. Interestingly, Honda's MC oils contain some moly.

The other additive to pay attention to is ZDDP, a zinc-phosphorus anti-wear compound. Due to EPA concerns about cat damage, most lower viscosity auto oils now have greatly reduced ZDDP content. This is a concern for some older engines with 'flat tappets', and could be an issue with our GL1800 engines. As I mentioned earlier, Ford saw such an increase in wear with some of the new formulas that it recommends against using them in any of their diesel engines.

From what I've read, many higher viscosity (40+) oils haven't changed as much. The current spec sheet for Mobil 1 15W-50 auto oil shows slightly higher zinc and phosphorus content than their 10W-40 MC oil. I've used Mobil 1 15W-50 auto oil exclusively in my 2 Valkyries and 2 F6Bs. In nearly 350,000 combined miles those bikes have been trouble free.