The BBC has excellent forum on this.See Below:
Please consult your owner's manual, or http://www.mercurymarine.com
for the BEST recommendations on each of these items!
This list will be updated as additional information is requested- check it regularly for the most current information!
-These are the "top recommendations". Refer to your owner's manual for other oil specifications!
-ALL EFI/CARB 2.4/2.5/3.0L (2-stroke) Engines: Mercury or Quicksilver Premium PLUS
-All STANDARD Optimax (75-250): Mercury or Quicksilver DFI/Optimax Oil
-ALL ProXS Models: Optimax/DFI Oil. Mercury or Quicksilver Premium PLUS is acceptable, but Optimax/DFI oil is RECOMMENDED due to a better additive package to help combat carbon deposits.
-ALL Racing/XS Models: Mercury Racing 2 Cycle Oil pn. 92-8M0078011, Mercury Racing Gear Lube pn. 92-8M0078015. Premium Plus oil may be used as alternative ENGINE oil.
- (Note..... there was some conflicting information on Merc's Website- follow this recommendation for the latest information as it's released!)
NOTE: Mercury/Quicksilver Optimax/DFI oil, and Mercury/Quicksilver Premium PLUS are totally compatible with each other. Although you should use the CORRECT oil, you can switch to the recommended Optimax/DFI oil, simply by adding the correct oil to the tank.