0 Anonymous Asked: October 5, 2020In: Technology Which is the best oil for diesel engines? 0 Which is the best oil for diesel engines diesel engine oil Share Facebook 1 Answer Voted Oldest Recent Dipesh Sinha 1 Question 9 Answers 0 Best Answers 39 Points View Profile Dipesh Sinha Added an answer on October 5, 2020 at 8:47 am n MOST diesel engines 15W40 diesel engine oil is recommended. Cars may be different. I have seen some that required 10W50 and some that ran 5W30. I think it depends on the model and how high RPM it normally runs at. Typically Diesel oil is much thicker, and has better film strength due to MUCH HIGHER compression in these engines. As far as brand goes, if you change oil regular, it is not a major issue. If you use conventional oil, 5K changes are very important. If your using synthetic, you can usually extend drain intervals to 8K easily, I have seen many folks extend all the way to 25K or more if the oil filter is changed more often than the oil 0 Reply Share Share Share on Facebook Share on Twitter Share on LinkedIn Share on WhatsApp Leave an answerCancel replyYou must login or register to add a new answer.