I have a Series 3 fitted with a Suzuki 2.8 diesel engine and 2 taxis with Nissan 2.7 diesel engines. I went on bay and found several good offers on engine oil, one of which was announced as Super Universal Tractor Oil 15W/30. I sent a message to the company asking if this oil was suitable for the above engines and they replied that it wasn't. Has anyone on here got any thoughts on this as I can't see the reason? Another tractor oil ad. selling the same sort of stuff but another name said in the blurb that their tractor oil was suitable for the smaller type of engine that I am on about. Opinions please.