This is an excellent article on synthetic oil that is written from both sides of the fence - no mumbo-jumbo..... just simple facts for the layman.
https://www.machinerylubrication.com/synthetic-oil-31800#:~:text=Under a microscope, a drop,different shapes, sizes and structures.
That is an excellent description of the matter...with a small (perhaps insignificant) error or two.
The opening statement is easy to misinterpret...but in plain English it says that “synthetic” oils are made from “petroleum” oils. So...in actuality... it may be better to think of “synthetics” more accurately as “more highly-refined” petroleum oil.
The advantage of that process is fewer “stray” molecules in your oil such as wax/paraffin, volatiles, and sludge-producing errata.
The misunderstood part is that “sludge” “varnish” etc are not as harmful as people think. Pistons, rings, bearings, etc which slide against each other (protected by a film of oil) actually KEEP sludge/varnish (IF it develops at all) from accumulating in places that might be harmful. Where the varnish/sludge does accumulate is along block sidewalls, valve-covers, sumps, etc. where it does not interfere at all with engine operation and where in-fact it actually PROTECTS AGAINST rust/corrosion because it forms a barrier to the water-vapor your engine produces. (Want to give your engine a good shot of dirt and filthy circulating junk?... it’s easy...use one of the snake-oils and “cleaners” that are sold aftermarket that your vehicle mfr’r actually never authorizes....and you can send all that crud circulating thru your otherwise fine-running parts.)
When fossil fuel is burned the primary by-products (besides heat) are carbon monoxide, carbon dioxide, and water-vapor. The first two and most of the water is expelled thru the exhaust, but some of those things get down into the crankcase where they mix with the oil. The water-vapor reacts with that oil to create the sludge/varnish but also to react with sulfur and other items to create an acid. One of the additives commonly used in lubricating oils is designed to counteract that acid.... But acid still exists and so does the water-vapor and that combination produces rust and corrosion which deteriorates engine parts.
While a good filter will keep most physical-particle by-products from harming the moving parts, the acidic-solution continues it’s work inside the engine.
What helps fight that problem? FREQUENT OIL CHANGES! Which is why non-synthetic oils and their more frequent change-routines do almost the same good work as synthetics... but for a LOT less money.
I don’t use synthetics except where mandated by my vehicle mfr’s. (My Ram P/U requires it in the differentials. My wife’s Toyota Sienna requires it everywhere. But my boat, my tractors, airplanes, construction equipment, mowers, etc do not and they all get ”mineral” oil.... standard petroleum products. My Jeep has over 330K miles on the cheapest mineral oil I could buy... WalMart’s SuperTech SAE30 motor oil, and the $2 SuperTech oil filters. Did SuperTech get that vehicle to 330K miles...?? I can’t say that. But what I CAN SAY is that cheap SuperTech did not PREVENT the jeep from getting that far!
I’m not one who trades cars every 3-5 years. I keep vehicles until I wear them out or wreck them, and I have not had ANY failures from plain ordinary mineral oil and frequent changes of lubes and filters. Even cheap lube and cheap filters. (Air filters are probably more important than any other.)
The math in the article is suspect, but otherwise a good explanation. Thanks for posting it.
BTW, the concern over 80W90 gear oil in cold weather is largely unfounded. In gear-cases where roller-bearings, hypoid and straight-cut gears exist (like front axles) the 80W90 oil is not underperforming compared to synthetic light-weights like UDT/SUDT. The sliding nature of those parts immediately shear the gear oil and it rapidly performs it’s work of preventing metal-to-metal contact. Differentials of older equipment in arctic conditions never suffer from the kinds of imagined failures discussed so far. In fact, before 1990 differential oils were almost never changed in the lifetimes of pre-90 vehicles because the engines wore out sooner. It was only after the introduction of “synthetic” gear oils that OEMs began to require 30K-mile differential gear oil changes. Think about that.
