I'm running Pennzoil's synthetic Syncromesh. I've had good luck with it. I have not added any FM to it. I'm on the fence as to if the full synthetic needs it. I may add a touch and see if it changes anything for high rpm shifting. I'm starting to think any full synth needs a small boost.
The Royal Purple sounds promising. It may need a boost of FM being full synth???
Specialty Formulations has a great reputation of making quality products as well. However their prices are quite steep once you add shipping. DO NOT BUY just quarts from them. The shipping will kill you.
