I have a 99 Merc 225 and wanted to know the best oil to run in it. The reason is my boss has 50 gallons of Mobil oil that he said I could have and wanted to know if it was safe to use. Mobil says they make oil for Mercury and would like to know if anyone knows for sure.

Just because it is Mobil Oil doesn't mean it is 2 stroke oil. Use what your manufacturer says to use in your engine. If it was me I would run the Mercury Premium Plus in it, but others have had success running other GOOD oil in theirs. What kind of oil is the Mobil? What viscosity? You may be able to run it in your vehicles.

TCW3 is the minimum. If it's a optimax it needs DFI oil. If it says anything else it's not right.

^^^ Yes. Optimax needs DFI oil. If not then you can use any TCW3 oil.

My 1999 225 Optimax owners manual says to use Mercury or Quicksilver Premium Plus.

Johnny

I have a 95 Merc 200 XRI and I use the Quicksilver Premium Plus. You can buy it at Academy.

First it is 2 stroke oil. The problem is I'm not sure if it is a dfi or efi. The serial # OG947171 won't pull on marine engine or boat net.

Should say on the motor if it's s efi or dfi ......

cowling has been updated and only has mercury on it

Does it have fuel injectors at the rear of the motor Like this http://www.boats.net/parts/search/Merc/Mercury/1999/1225494VD/FUEL%20RAILS/parts.html? If yes it is DFI. Injectors on front http://www.boats.net/parts/search/Merc/Mercury/1999/1225423VD/FUEL%20MANAGEMENT%20SYSTEM/parts.html its an EFI.

Thanks Gary. It is like the second one so it is an EFI. So what oil is best to use?

You can use the Mobile as long as it shows a TCW3 rating.

Reason your number doesn`t show is the way you entered the first symbol, it is number 0 not the letter O.

You really need to find a manufacturing label or stamp.

There is a good sticky pinned over at Bass boat Central in the Mercury forum that gives all the details for oil. It's under the FAQ.