A buddy has been staying with us for a few months and I've let him use the 850 as his own while here. He changed the oil about a month ago. I've just noticed a can of diesel oil which he mistakenly bought and used in the 850.

The car runs fine but should I be worried? I've heard it can damage seals in petrol engines. I've also heard some people use it on purpose. Can I wait until the next service or should I change it now?

 

I see no problem running a diesel oil as long as it is the correct weight, ie. 5w30.

I run Shell Rotella (Shell Rotella® Products - Shell Rotella) diesel oil in my Jeep Cherokee and have been for over 3 years. The Cherokee just hit 190k miles and still runs like new. Diesel oil has a higher level of Zinc (ZDDP) and is better for flat tapet cam engines, like whats in the Cherokee.

If it bothers you, just drain and fill with fresh oil.

 

its 15w40 which isn't far off the recommended 10w30 or 10w40 from the castrol site. temperatures don't get that low here so probably a thicker grade then the US.

 

Thats not bad at all. Its on the heavy side but should be fine for your climate.

 

I exclusively run synthetic rotella in all my motorcycles and have no issues there either.

 

haven't seen the stuff in any of our shops

 

I got tired of buying different grades and types of oil for the
Mercedes Diesel, Jeep GC, Jeep CJ, Suburban, and the Volvos (S60 and my old 960).
I few years ago I standardized on Rotella T6 Synthetic 5W40 and all my vehicles seem happy. The oil leaks that Mobil1 Turbo Diesel oil caused in the Mercedes went away and the gassers stay cleaner as the Diesel oil has more detergents in it than regular gasser oil.

 

That weight (15W40) is not the best oil for your winter now. On the other hand, diesel oil has some things in it that are very good for our old engines. I wouldn't worry about it.

If your car is Turbo, it is more important for the oil to be synthetic.

 

The temperature doesn't get below freezing often (certainly not during the day) so that weight is pretty common/popular here.

 

Diesel oil in the engine is fine...as long as you start using diesel fuel.

 

I dont think you would have any damage but I also would not leave it in there. We are talking a small amount of $ to change it....why risk it?

Here is a write-up that explains the differences.
What Is the Difference Between Gas & Diesel Engine Motor Oil? | eHow.com