(quoted from post at 08:04:47 12/04/17) Ok, time for a little more info on oil. First and most important; "Full synthetic" is not synthetic at all. Not full, not partial, not mixed, not synthetic. You can believe me, or go study the MSDS for EVERY mfg syn oil. Somewhere hidden in the gobbledegook wording will be the fact that it is a hydrocracked, highly refined petroleum product. It all comes right out of the ground, and not from any lab. It started from one of the mfg calling their refined oil synthetic, and Mobil suing them. The upshot was that now, there is NO synthetic oil in the US, except some highly specific racing oils that are not sold retail.
Next. Oil changes. Back when we were kids, engines were loose. You know that, everyone just forgot. A 40wt oil was what we used to keep the metal from touching other metal, and it worked pretty good. Today, the clearances in a modern engine are about 1/4 to 1/10 what the clearances were back in the 60s. If you were to run a modern engine on 40wt, the molecular binding would very soon leave the bearing high and dry, and that would be the end of that. Today's weights are 10w-40, 5w-30, and in some cases a 0w-30. These are thin, thin oils, with a very light base. Because of such a light base, they do not hold products of combustion well, and they do not hold the friction modifiers which make them multi-vis capable well. There is always broken chain molecules happening with these light base oils, so oil change on time is even more critical. You can ask some MB owners about that, because MB had the pleasure of replacing hundreds of engines when they tried to up the change interval too high.
Further, the tightness of the emission system on modern engines don't allow them to blow off the products of combustion like they used to, so the oil tends to dilute much worse, and this is very serious on cars which are not run long and hard, but short cool trips that don't boil off the contaminants. If the mfg change interval is 15k miles, follow it - or suffer the consequences.
Next, additive packages. This is where each mfg gets to shine, or fail. Everyone has opinions on oil brands, and I will share this with you - when Mobil came out with their aviation Mobil 1 synthetic for piston aircraft engines, they are the only mfg that has actually killed people from an known oil failure in flight. You can look that up at ntsb.gov if you are that interested. I will not use a Mobil/Exxon product ever again. I also know for certain that various auto mfg get marketing deals from various oil makers to specify their product. Porsche worked with Shell for many years, and now works with Mobil.
Finally, what to use? P66 is an expert in industrial lubricants. Also aviation oils and fuels. So is Shell. I would say it's hard to go wrong with a brand that makes aviation products, and also commercial lubricants for oil field, machinery, mining, etc. I've been using Valvoline, Shell or P66 exclusively for years, and have yet to suffer any oil related failure. My only complaint about Shell is that they rarely offer any financial incentives or sales. Once in a while, but not as often as Valvoline. I tend to stay away from the PA crude(Valvoline, Pennzoil) because they start with a very high ash content due to the nature of where they are getting their crude. I use Castrol 2 stroke oil in various two stroke engines and have had great success with that, so I stick with it. I'm sure Shell makes a good two stroke oil as well, but I'm not changing unless there's a major reason.
