Many of you may well remember my reaction to GeorgeCLS’s announcement last year that the newest formulation of Mobil 1 (SuperSyn) did not contain any esters. Given how modern synthetic oils are built, and the need for some ester in the mix for solvency and seal swell, I was completely unwilling to accept the assertion that Mobil 1 is now “ester-less” at face value. It didn’t help that George’s explanation was that Mobil had invented a PAO that could handle the solvency and seal swell issues on its own. I didn’t buy that at all, especially since my own research had revealed that the “new” ingredient in Mobil 1 SuperSyn was in fact ExxonMobil’s proprietary high viscosity, high VI SuperSyn PAO. I had always assumed that SuperSyn’s pour point was higher than the old Tri-Syn because of the addition of this much more viscous PAO, not because the base oil esters had been removed from the mix. There simply didn’t seem to be any plausible basis for believing that Mobil 1 was now being built without base oil esters. Fast forward to just a few days ago when someone posted about the article detailing XOM’s development of a PAO/AN based oil that was ester-free and my thinking suddenly began to turn around. After mulling this over, I have taken a 180 on this issue and I’m now willing to believe, no, make that DO BELIEVE that Mobil 1 SuperSyn contains no base oil esters. The answer as to how they could do this was right there all the time in the form of the third “synthetic fluid” utilized by Mobil in the making of the Tri-Synthetic formula: An alkylated aromatic. Even with the Tri-Syn Mobil 1, it’s pretty obvious Mobil1 was trying to reduce the level of ester needed by utilizing the alkylated napthelene. If the ultimate goal was to eliminate the base oil esters completely, the Tri-Syn formula was the first step. Success came when they decided to thrown the SuperSyn PAO into the mix. This extremely high VI PAO could no doubt take a higher treat rate of the alkylated aromatic. The AN coupled with an esterized additive package handles the solvency and seal swell issue without the need for base oil esters. SuperSyn’s pour point and Noack numbers are not quite as “good” as Tri-Syn’s because the base oil esters aren’t there anymore. The alkylated aromatic is naturally going to be more volatile than a good stable base oil ester. And the high viscosity SuperSyn PAO is not going to have as low a pour point as the lighter grades of PAO used in the Tri-Syn formula. (I’m not saying SuperSyn is the only PAO used, but the addition of any is going to have a negative effect on pour point.) Given that Mobil 1 SuperSyn shows superior UOA numbers to the old Tri-Syn, I’d say Mobil has pulled the proverbial rabbit out of the hat: They have built a version of Mobil 1 that is cheaper to produce (because of no base oil esters) and yet performs better than the product it replaced. That’s where my thinking is now on the whole issue of Mobil 1 being ester-less. I believe it is, and I believe the SuperSyn PAO and the alkylated aromatic are what enabled Mobil to do it. So while I think GeorgeCLS’s explanation of how Mobil was able to do it was way off base, I now believe he was right, and I want to publicly apologize for the not-so-kind things I had to say to and about him at the time.