Diesel oil in Merc 3.0l?

[Simoniz]

Ive got some 10w40 turbo diesel engine oil left over from when I last had a diesel engined car. Can I use this in my Mercruiser 3.0l petrol engine No OL634881?

We know any grease is better than no grease at all but does the same apply to engine oil?

 

[Rick Stephens]

Diesel engine oil is very high detergent. In an older engine that has never run a high detergent oil it can be a problem. All the carbon deposits that build up over time determine many of the tolerances in older motors, especially rings, but even bearings. Adding a high detergent oil will break down and start removing those, next thing you know the motor loses compression and possibly even spins a bearing.