Originally Posted By: Quattro Pete
Originally Posted By: weasley
Because the HTHS requirements are minima. C2 requires 2.9 cP minimum whereas C3 requires 3.5 cP minimum. If you have an oil of, say, 2.8 cP then it meets both requirements.
LOL! What kind of alternative math are they teaching you over there in the UK?
To use an American phrase that has embedded itself in the British vernacular..... D'OH!!
Of course I meant that if an oil has a HTHS of 3.6 cP, it meets both. I was multi-tasking as I typed before and got my max and min all discombobulated.
The point is, you can achieve both specs with one oil, if HTHS is your only test. There are some other phys/chem and performance differences between C2 and C3 as well, for example:
C3 has a minimum TBN of 6
C3 has a maximum phosphorus of 900 ppm
C2 has a higher fuel economy limits in the M111 engine test
C3 has tighter limits in the OM646LA engine wear & cleanliness test
C3 has tighter limits in the VW TDi wear and cleanliness test
So, if you can pass all of the tests to the tighter limits with the higher HTHS, restricted phosphorus and minimum TBN then you can get both specs. This isn't a trivial matter - note that you have to achieve the better fuel economy limit of the lower HTHS spec.