We buy our oil in 205 litre drums for use in tractors / plant etc. I spec an oil which is suitable for use in turbo diesels as well as petrol engines. The last lot was Exol. Its a 10w-40 G5 / CH4 mineral specification.
Have used Fina, Castrol and Esso in the past.
It doesnt really matter what brand it is, the spec is much more important.
Tim..