Originally Posted By: UltrafanUK
I've tested C3 oils (Castrol Edge TD 5w40 etc) and they double the wear metals in a TDI UOA.
What 'test'? Bench test? Dyno-driven engine test? Or single data point, no reference, uncontrolled external factors kind of test?
Originally Posted By: UltrafanUK
Some manufacturers...
Which?
Originally Posted By: UltrafanUK
...including Castrol...
Where?
Originally Posted By: UltrafanUK
...claim a C3 oil is backwards compatible with A3/B4, which is total rubbish unless the oil has Moly, Boron AND Titanium, which some expensive FS oils do, including the most expensive Edge 0w40.
If you read the Acea specs there is a specific warning about both C2 and C3 oils which Castrol and some OEM's ignore.
The "warning" regarding the 'C' category oils is this:
Originally Posted By: ACEA 2016 oil sequence
Some of these Categories may be unsuitable for use in certain Engine Types – consult the vehicle-OEM’s owner’s manual/handbook in case of doubt.
But they also say this...
Originally Posted By: ACEA again
These Oils will increase the DPF/GPF and TWC life and maintain the Vehicle’s Fuel Economy.
Originally Posted By: UltrafanUK
...at present the best Acea specs are A3/B4 if you are DPF free. Some folks think the E spec oils are better, but that's another adversiting myth, although they are closer than the C specs.
The 'best' ACEA oils are those that meet your vehicles needs. You might argue that an engine wanting ACEA A5/B5 would be best served by an A5/B5 oil, rather than getting bogged down by an A3/B4 oil. And who is "advertising" that E oils are "better"? Those oils are for trucks and busses and are specified appropriately.
Originally Posted By: UltrafanUK
PS: C4 has even lower ash than C2/C3, so unless the oil has a GTL or Synthoil base, I would not use it. The Ti oils that have a real G4 or GTL base are rather too expensive.
How many oils have you actually formulated? You seem to be randomly picking base oils or chemical elements and holding them up as the solution to perceived 'poor' specifications. The whole reason there are several specs to choose from, is because there is no one-size-fits-all solution. The wear requirements of ACEA C2 and C3 (and now C5) are actually tougher than for ACEA A3/B4 (note also that ACEA A5/B5 wear limits are the same as the C categories, ie tougher limits than A3/B4).
Originally Posted By: UltrafanUK
I do look at an oils VOA, but no one seems to publish chemical compositions, so I just work in the real world of ultimate block life lubrication. In that world C2 and C3 are such a bad joke that one school of thought says don't use them as the resulting extra wear factors visible in a particle count will increase the oil consumption in the long term enough to outweigh the advantages of low ash. I'm in the probably does not matter unless you use an HDEO with higher Zinc-Phos levels in an attempt to find out how expensive a new DPF or CAT is.
So all those millions of VW/Audi/Skoda/SEATs, BMWs, MBs, Fords and myriad other cars running around on mid-SAPS oils with no problems have all got lucky? How are C2 and C3 such a "bad joke" in the real world, given that the oils that meet them have to pass tougher testing than your revered A3/B4?
I'm not saying A3/B4 is bad, far from it, but it isn't a universal panacea.