Now this IS interesting. Yesterday someone started a discussion about base stocks in current conventional oils under the heading of, "
How many companies still use Group I?. I responded that I felt no one used Group I these days, and noted that prior to the release of "SL" oils, even
Equilon Havoline touted their use of Group IIs in their "SJ" rated oils on the backs of their bottles. What followed were several responses suggesting that up to 70% Group I base stocks are still in use in conventional current ("SL") oils. All based on, "Someone said..." or "I heard..." Over a year ago I downloaded a white paper from Union 76 about the then (dated June 11, 2001) upcoming debut of "SL/GF-3" motor oils" titled, "API SL/ILSAC GF-3 NEW SERVICE CATEGORY FOR PASSENGER CAR MOTOR OILS". On page 6, Union 76's position was that, "In order to meet these stricter volatility limits, API SL/GF-3 oils require the use of higher qualtiy base oils, especially for the lighter (and preferred) viscosity grades. SAE 5W-20 and 5W-30 oils cannot be formulated with 100% Group I base oils because they will not meet volatility limits; they require high percentages of Group II or Group II+ quality base oils." I may have been guily of overstating the use of Group IIs currently, but not by much. And I believe the case could be made that, after more than a year down the road (pun intended) with "SL" motor oils, the use of Group IIs generally is likely more than it was when the "SL" oils debuted. As speculative evidence, all the backs of various "SL" rated oils I've bothered to read, regardless of viscosity range, tout something along the lines of:
1> "Improved anti-Wear properties"
2> "Less oil consumption"
3> "Better fuel mileage"
4> "Better freedom from sludge and varnish buildup"
Advertising hype buzz phrases? Of course. But, there just may be a grain of truth to these claims, too. As for #1, most of us are aware that the reduction to trace levels of sulfated hydrocarbons and aromatics in Group IIs results in more of the desirable iso-paraffinic lube molecules. As for #2, both the previously listed undesirables are known for their instability and volatility at high tempratures, so their reduction from previous levels common to solvent refined Group Is would logically result in an improvement in oil consumption, too. As for #3, the conversion of residual wax to iso-paraffinic lube molecules (hydrogen isomerization) results in a higher viscosity index in the Group II base stocks. It would follow cold starts and drivability would improve, as would high temperature lubricity. (Aromatics make great solvents but terrible lubricants.) And, as for #4, those undesirable and unstable sulphated hydrocarbons and aromatics release free radicals (charged particles) when they break down just itching for the opportunity to encourage oxidation of other molecules. It's a vicious cycle that further encourages sludge and varnish formation.
As to the debate of Chevron Texaco Havoline vs. Chevron Supreme, look up both products' product data sheets and material safety data sheets. They read IDENTICALLY in ALL categories for ALL viscosity ranges except for the listed ASTM D 2896 Base Numbers - the Havoline is 0.2 HIGHER down the line than Chevron Supreme. I'm skeptical that Chevron would intentionally formulate their company branded premium conventional motor oil to a lesser quality level than that of their merger acquired Havoline name brand. Again, I could be wrong, but I'd bet this "discrepency" was either the result of a typo or sampling different production runs. Even if it was intentional, I don't see much (any?) practical performance difference significance between Havoline 10W-30 at 7.6 vs Chevron Supreme 10W-30 at 7.4, but, maybe I'm missing something... As far as I'm concerned, I'd buy either of these "brands" on price, and if I had to top up, I wouldn't lose any sleep at all which "brand" I did it with.