Can I mix 25w40 with 15w40?

[Simoniz]

Ive got Quicksilver 25w40 mineral oil in my Merc 3.0l motor right now, do you think it would be OK to top up with some 15w40 marine oil which I have (made my Liqui-Moly, by the way)?

 

[Bondo]

Ayuh,..... I would,..... without a 2nd thought,.....

Exchange the word Oil, for the word Grease in my signature,.....

 

[Oshkosh1]

No problem whatsoever...I'll go further and say that even IF one were dino, one were synth you'll have no issue.

 

[boobie]

I wouldn't mix them but it's your motor. JMO.

 

[HT32BSX115]

No problem whatsoever...I'll go further and say that even IF one were dino, one were synth you'll have no issue.

It won't hurt a thing, and I wouldn't hesitate to "top-up" with any 4-stroke automotive motor oil! dino or synth, single or multi-grade!