So I found this website https://ukla-vls.org.uk/ of an organisation that tests oil independently and publishes the results. Specifically they deal with claims where the oil specs claimed by the manufacturer are not met.

Interestingly there have been a few cases of oil supplied by Westway not meeting the claimed specifications. Although there does not seem to be a case relating to 5W30 JLR spec oil it does make me wonder if I can trust Westway (and other small suppliers) more generally and should just stick with Castrol to be sure it is to spec.

Find one with the necessary approval in place instead of the terms "meets" or "complies with" etc.

If they have the word approval, they have been tested to meet the minimum relevant standard.

If they are "meets", it is simply a manufacturer claim.


The TDV6 uses 5W-30 C1 oil which is a little more difficult to get hold of. My personal choice for C1 is Petronas 5000 FJ, which has the necessary Ford and Land Rover approvals. Lots of forum members use Smith & Allan F, which is a Shell base, albeit the Smith & Allan doesn't claim to have the approval.

N.b. if you read the investigation notes for Westway Oils, it looks like it was a marketing error - it was a C3 oil with A3/B3 compliance listed on the back, which they later removed. 2015 Range Rover Autobiography 4.4 SDV8

I used to work for Castrol. All oil manufacturers, including premium formulators like Castrol, on the automotive side of the business will use an additive company package from an additive company, such as Lubrizol, Chevron, BP's Adibis (sold to Lubrizol), Mobil, Lanxess and blend those to attain a product meeting specifications. Specifications can be industry specs like SAE, DIN, AP, Military or car manufacturer specific.

So pretty much all oil marketing companies will blend mineral oil with a bought in additive package at a ratio advised by the additive company. The additive companies will do all the specification approval tests before marketing their package. With mineral oils, in the UK there are only so many refineries left to go to; two last I know of. So and and all lubricant companies in the UK will be using limited options on mineral oil supply and additive packages available to meet a specific specification.

Therefore oil from company A will be pretty much the same as from company B unless it is for a highly specialised application when a unique package may be developed exclusively for a marketer, like Castrol, in cooperation with an additive company. The only caveat is if companies blend from recycled oil, that isn't as good thermally and oxidatively as virgin oil. So that is the only question worth asking if buying to a meets or exceeds specification product. Castrol would never use recycled oil when I worked there.

With blending formulations there is a range. Say oil A has an additive package from Lubrizol blended at 6.8% to meet a specification. There will be a blend range, it could be 6.6% to 7.0% to keep the specification parameters within spec on things like base number and viscosity. Your more budget blenders may well take that as an opportunity to blend at 6.6% because additive packages are expensive, so savings can be had replacing package with mineral oil.

That’s really interesting Baz and useful background info from someone who has knowledge of this from inside the industry.

It sounds like it is a very similar situation to the whole petrol/diesel debate as to whether premium fuel is better than standard.

As I am doing oil changes every circa 5k miles I think I will go with an oil from an independent blender that has the right spec rather than the full ‘LR approved Castrol’ oil.