we are buying texaco high grade 15w40 diesel engine oil (for euro4) for £1.50+vat/Litre in 205l barrels.. most of these name brand oils are a fancy can & some clever advertising..
silkolene oil (now FUCHS) was legendary for being made from recycled old oil, and it was the only oil allowed on concorde. it had a fabulous reputation back in the day, no hype, just honest oil. they made loads for oe aftermarket too