I went back and re-read Bruce's comments. He doesn't seem to contradict Ron. He actually seems to agree on the main issue, GrpIII almost as good as GrpIV.
Ron,
The scientific method requires not only a single experiment producing certain values, but multiple experiments by multiple people and different places being able to reliably produce the exact same results. Therefore, it is not valid to collect a few numbers for few oils, compare them and then make all sorts of broad conclusions. I think what Blazer & Co are trying to say is that you need much more info/data for bigger/broader conclusions.
If I understood Bruce, IIIs need much more additives than IVs. Hence chances are much higher that the additives will be "spent" over time thus depriving IIIs from their effects.
Ron, assuming 100% correct data ion spec sheets from companies, the comparison is not important at T0 (when you put brand new oil into motor) but instead performance at T1, T2,... (1-2-3 months hence). How fast are additives spent in IIIs and IVs and how oil characteristics change, etc. Clearly there are no spec sheets for T1,T2,...
Lacking such data, we (amateurs) cannot do much but guess and extrapolate, so much so that end conclusions are likely to be way off. No point. The few professionals who work in the industry likely have access to much more data, as well as much better unerstanding of the chemistries, etc. So they are much better equiped to make conclusions, etc.
Since the issue of additives and their loss has been brought up, I have a couple of questions. First and foremost, what exactly is the rate of loss of additives? Sorry, I know, very broad question, engine type, additive type, etc. I am just trying to get a feel for it. Are they mostly spend after 2-3 months, or 6 months or ...? For instance, if you have an average commute to work car (say 2ishL, I4) and do mundane 50/50 city/highway commute to work. Then if I used one of these new GrpIIIs for a mundane 6month/5K OCI, will additives will be shot to ****? Mostly spent or half gone or ....? Again, just a feel.
If these additives in IIIs can hold up for a non-long OCI and GrpIII oil can maintain comparable characteristics to GrpIVs, in particular CCS/MRV for the coming winter, then the original premise that IIIs can be as good as IVs seems to be more or less correct, no? Not sure if I'd go as far as to say IIIs are better?
Anyway I am just wondering about additives and how robust they are. As far as pricing, while many people complain about Castrol Syntec being as expensive as M1, at least in Canada I believe we have other GrpIIIs that are much cheaper. And for those of use who have small sumps (small I4 Hondas, Mazdas, etc) the long OCI is not a good idea anyway.
