Hey, Pete! Thanx for the vote of confidence.
...otherwise emotional subject of oil.
Yes, it is. Well, I guess I dunnit again. Got drafted into another 'war'.
On one side of the fence is the hard science and chemistry of the petrochem industry.
Then, there's us consumers.
In between are the marketing and sales guys, who try to boil it down, then spice it up.
No wonder we're confused.
I got deep into this back in the '80s, with the hotrod & airplanes & Amsoil & Aeroshell Synthetics.
Maybe you got into this with your Skymaster.
But, that stuff is now oldschool, and I'm trying to catch up.
It's a huge (*gasp*) industry.
... I would really like to hear your scientific take on the theory of crushed Polymers in multi viscosity oil, especially in engines with ball and roller bearings on the crank like the XS650. I also understand that synthetic oil achieves it's multi viscosity characteristic without the use of Polymers and is therefore not subject to the phenomena of crushed polymers reducing the effective viscosity. Were it not for the super high price of synthetic oil, I would probably use it but the high cost is a deterrent to frequent changes which are dictated not just by the specter of crushed polymers, but also because old air cooled engines have a lot of blow by and the oil gets dirty fast so frequent oil changes are called for.
There's some old documents (that I haven't found on the 'net, yet) that showed the viscosity degradation curves of straight weight oils, versus multi-vis oils. Straight weight oils have a rapid reduction in viscosity with temperature, while the multi-vis oils have a bit flatter curve.
Essentially, when you view these viscosity charts, you can see the intersecting lines that show, for example, a multi-vis oil having the same viscosity as a 10wt at freezing, but it's flatter curve shows it intersecting the 30wt at 212°F. Hence, it's labled as a 10w-30. Some folks would have you believe that the oil 'thickens up' at higher temps. Actually, it's just a less aggressive viscosity reduction.
The synthetics, due to their stability, also demonstrate these flatter viscosity degradation curves.
But, to avoid confusing the public, they often get the multi-vis labelling, like 10w-30.
Remember the public outcry when Shell Syntec was simply labelled as 10wt?
I'm contemplating a different approach to this, sort of a 'flanking' maneuver. (This IS a war, right?) The preamble to this would be in a new thread. Planting the seeds, so to speak.
... And please verify that synthetic oil is not really synthetic. It is still formulated from crude petroleum but they somehow break down the oil and "synthesize" synthetic oil at the molecular level.
Some of the newest stuff comes outta natural gas. You're hitting at the heart of the industry, building and breaking down long-chain hydrocarbons. Quite complicated, with protected propriority processes. This stuff fills books. I'll see if I can simplify it.
... You're from Texas. You know all this stuff!
Haha, how did you know? Yes, in addition to Texas History, Texas 'Gold' was required curriculum.
I still remember elementary school studies, where we had to draw cracking tower schematics and name the various products. I wonder if that's still taught.
For now, the Bobistheoilguy site is a good resource, as well as factory recommendations and good consumer testimony.
I'll put together something for a new thread...