mixing old tri-syn 15w50 with new 5w30 supersyn

[1 FMF]

A buddy gave me 3 or 4 quarts of mobil 15w50 synthetic that he had for a while. It says tri-syn on the bottles, I would say it's maybe 5 years old. But they're unopened. Think I could mix this with new mobil-1 5w30, just to get some use out of it? I don't have anything I really want to run 15w50 in, other than the 351w in my boat.

 

[Jelly]

Just don't run it then...believe the old tri-syn version was never really that good anyways.

 

[Patman]

I say use it for the boat.

 

[KW]

Mix them and use them or save them for toping up.