Not unless it's a version specifically meant for Diesel, The oil meant for diesel application's has a very high amount of detergents with relation to other oils because diesel's run so dirty, You should also be very careful not to come into contact w/used diesel oil too often because it's known to cause health problems later on. The only reason they're exempt from emission testing here in Ga and many other locales is because they don't create ozone harming emissions
There are plenty of snythetic diesel engine oils. The newest rating for a diesel engine oil is CI-4. What spec does the engine on the mower call for.
I run synthetic engine oil in my Cummins engine in the truck only for the enhanced cold weather properties of the synthetics, but if I had a diesel powered mower I'm not certain I would run synthetics in that. Given that it is only run in the warmer months I would probably stick with a conventional 15w40 diesel rated engine oil.
Actually I probably would run synthetics in the diesel powered mower if I owned one but only in the interest in keeping fewer oils on the shelf. If I did not drive a diesel powered truck that I was running synthetic oil in I would not run synthetics in a diesel mower.
This was taken from the Mobile 1 site................................................
Myth:Mobil 1 can't be used in diesel engines.
Truth:Mobil 1 with SuperSyn will provide excellent service for passenger car and light-duty truck diesel engines (API CF or CD), as well as European diesel cars that require ACEA-quality oils. (This is the oil specification used in Europe and developed by European car companies.)
Heavy-duty truck engines that require API CE, CF-4, CG-4, CH-4 or CI-4 should use one of the products from the Delvac® line Mobil Delvac 1® synthetic engine oil or Mobil Delvac 1300 Super®. Mobil Delvac 1 synthetic oil can help improve fuel economy, extend oil drain intervals, extend engine life, provide enhanced wear/cleanliness protection and reduce oil consumption. Delvac products can be purchased at a large number of truck stops across America, some retail stores, auto parts stores and from ExxonMobil distributors.