returning to the question- td5 oil- recommended oil is 5/30- 5/40w- service intervals are 12k and LR originally recommended Mobil 1 synthetic.- this is what they used to use at the dealers when i used to take it to them. now i do my own services i have used 0/30w (silver hook), 5/40w (halfords/mobil 1, and now 5/30w (unipart synthetic big tub) all synthetic. they is a lot of info re oils on internet - alot of which i dont understand but i think a lot of HGV now use longlife oil lasting 20,000+ miles and some fleets do oil tests to see if new oil is needed. using an expensive oil and dumping it at 5000 miles would be a false economy. but depends on your driving, load , towing etc i think. but a decent synthetic should last til the 12k service interval.