I'm about to do a full maintenance change on my 91' 300SE and was hoping for some recommendations on some of the best parts to use.

OIL:

I've heard and seen great things about Royal Purple oil. If I do buy a synthetic this will be it. However, I'm aware that most engines don't need to run full synthetic and in many cases it's complete overkill. Yet, the M103 is a high revving engine, and I'm wondering if it would be useful to run a full synthetic oil in this engine.

Another concern would be the effect on the seals of this engine going from dino to syn. Would full syn quantifiably change the structure of the seals, possibly causing leaks?

Also, is it OK to run API grades higher than OEM recommendations for further protection against wear? I was considering running 20w-50 during the very hot Texas summers, but I'm not sure of the effect this would have on the engine besides reducing fuel efficiency.


OIL FILTER:

I've normally used FRAM but I'm hearing from many that this is a very poor quality filter. Suggestions?


AIR FILTER:

Again, I've normally used FRAM but I'm hearing that this is a poor quality brand. Is K&N a much better choice? What would be the best choice for this motor?


SPARK PLUGS:

There was just recently a post about this very topic but it quickly derailed into argument about circuitry. How about some quick suggestions on best personal experiences?



I think I've got the rest of my bases covered, but I'd enjoy hearing from you all about any other maintenance products you've had positive experiences with.

Thank You.