I personally run Pennzoils Premium Plus in my 225 Opti. My plugs look great and my prop hub is much cleaner the when I ran the Merc oil. Thats good but not the only thing an oils compatibility should be based on.
Merc will never certify another manufacturers oil for use in their engines. They want you to believe that their engines and oils are so unique that they must be used together....unless you want to use their oil in another brand of engine which is OK too
Tohatsu's TLDI is very similar to the Mercury Optimax. They both use Australian company Orbitals technology for fuel delivery. Tohatsu has a list of oils they certify for use in their TLDI engines. That list includes Pennzoil Semi Synthetic and full synthetic as well as a bunch of other quality oils. These are oils that Tohatsu has tested in their engines and feel they meet the requirements of their DFI platform.
Someone should call Merc and tell them they live in some obscure location and can't get Merc oil for their engine. It would be interesting to hear what they recommend.
Here is the Tohatsu information:
"What kind of oil do I need to use in my TLDIŪ?
You will always need to use a high grade TCW3 oil designed for use in Direct Injection motors. Regular TCW3 outboard oil is not recommended for use in the TLDIŪ models Most outboard companies offer a high grade/premium TCW3 oil designed for use in Direct Injection motors. The following oils have been tested by our factory and certified for use in TLDIŪ motors:
Tohatsu Premium Oil
Nissan Marine Premium Oil
Pennzoil Complete Marine Synthetic
Pennzoil Semi-Synthetic Outboard Oil
Mercury Optimax/DFI Oil
Yamaha Yamalube 2-M Semi-Synthetic Injector Oil
Bombardier RAM Ficht Oil
The above oil brands are currently the only brands that have been tested and approved by our factory for use in TLDIŪ systems."