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I don't know about over there but here in canada we have blended oils on the menu as well. They are made by Mobil, Esso,Petrocan and one other that I'm having a brain freeze on (Shell maybe). They are only made by the companies that have the refineries. In a couple of lubrication courses I took for work, I was told that the blended mineral and symthetic was superior to just synthetic, you could change the oil later than the mineral oil but before the synthetic. They told us that mineral oil, has various length lubrication molecules. All oils that are run in engines, the lubrication molecules and the polymers get sheared over time. If you had a full synthetic oil (which is made from all the same length molecule), over time it also gets sheared and your base lubricant would thin below it's original viscosity and leave a poor ( more Poor compared to mineral oil) film in the load bearing zones. Poor of course being relative ! If You had a blend of synthetic and mineral oil then the various length lubricant molecules in the mineral oil, would make up for the shearing of both synthetic and mineral. The mineral oil had longer lubrication molecules and could afford some shearing. The synthetic portion added it's benefits to the blend. Oh yeah, the mineral portion performed better in the inital start up, drained bearing and no oil pressure load protection (you know what I mean) than the synthetic, which relied on the polymers to keep it thick when cold. If the polymers were sheared to some degree then the full synthetic would not get to it's designed cold viscosity.
This forum stuff is new to me and it's amazing how long this gets compared to a verbal converstion. The information exchange is really hard here. I've been really sick this week, does any of this make sense?
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