Diesel engine oil discovery V. Went to the dealer last week and the oil that they gave me for my diesel discovery 2017 was a 0W30 weight oil which is not listed in my manual. The parts guy said this works in all the cars. I don't want to use it for obvious reasons if it's not the correct oil. Anybody else hear this. Thank you!

 

I would suggest a 5w-40 meeting ACEA C3 spec. You want the 40w to help protect your bearings and cam lobes, and an ACEA C3 spec will be safe for your diesel SCR/DPF. ACEA did away with the C1 spec earlier this year. Ford F150 manual says if you run any biodiesel to use a 5w-40.

 

What's printed on the bottle label for the consumer is not necessarily the same viscosity of the oil. There are a range of viscosities that qualify to be categorized a 30w or 40w. A thick 30w has similar properties to a thin 40w.

As for wanting thicker oils to protect bearings and cam lobes-that's not quite how fluid dynamics works. We spec the oils that we do based on clearance, stress, duration, capacity and intervals.

The majority of engine wear tends to occur when cold engines are pressurizing and that's exactly where thinner oils come into play. Now that we're able to manufacturer at much finer tolerances the need for a thick viscosity is virtually eliminated. In fact, you'll find that many race engines that are built to tight tolerances run 20 weight oils or thinner. Additionally, thicker oils can actually create more heat due to increased friction.

I've been in the industry a long time and I know petrol-heads and enthusiasts always seem to correlate thicker oils with superiority, but that's not the case. The oil viscosity required is entirely dependent on the tolerances of the engine and the expectations placed up on it.

In the wintertime especially you'll be much better served by the LR spec oil. Please use what we specify in the manual for your given model year.

 

I was using the Ford oil. Now Mobil ESP 5w30 meets spec. That's what I'm using now.