Another take on oil

Bryn

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This is an interesting post from a guy over on the Super Tenere forum...

An interesting read :cool:



'Actually, for internal combustion engines with pressurized oil circulation and filters synthetic blend is superior to synthetic.

I used to be a "full synthetic in everything" kind of guy. Way back in the day I even used and sold Amsoil. But about a decade ago I bought a piston airplane. Keeping the airplane engine running well is more important in that than my Ford F350 diesel, Lexus IS, Yamaha Super Tenere, John Deere and Kubota tractors, Kubota Zero Turn, generators, air compressors, etc. So when I went looking for a full synthetic piston airplane engine specific oil and could not find one I was curious as to why not?

I found an excellent article written by an Exxon oil engineer that answered the question. While synthetics have superior anti-corrosion, shear strength, resistance to break-down at high temperatures etc. they do have three negatives.

First, they are more expensive.

Second, full synthetic oils do not have the natural solvency of mineral oil.

Third, full synthetic oils do not suspend particles as well as mineral oil.

So in an application where there is no pressurized circulation from a pump and a filter - say in a rear end / differential full synthetic is superior.

But when there is a pump and the oil circulates and eventually passes through a filter a synthetic blend is superior because it can suspend particles (combustion by-products like carbon, wear items like small metal particles, even dirt, etc.) and carry them suspended in the oil until it passes through the filter medium and is caught.

Full synthetic oils do not do as good a job suspending particles so the abrasive particles end up dropping out and gunking up the lower areas where oil is present rather than being filtered.

Mineral oil (non-synthetic base stock) also is a more effective solvent than synthetic.

So given the choice between non-synthetic, synthetic blend, and full synthetic the best choice for engines with a filter is synthetic blend as it combines the benefits from both types of oil.

No manufacture makes a full synthetic piston airplane engine specific oil because the airplane engines are not water cooled so they have more combustion by-products than water-cooled / temperature regulated engines. They also burn fuel with lead so there is lead residue in the combustion blow-by that gets into the oil.

One manufacture did make a full synthetic piston airplane engine oil for a time - Phillips - but they ended up buying some airplane engines after valves stuck because the lead particles were not broken down by the solvency of mineral oil or carried to the filter and filtered out by the particle suspension capability of mineral oil. So the lead particles stayed in the oil and built up on the valve stems and caused valves to stick. So they stopped making the oil.

I use Exxon Elite which is a synthetic blend and I use Rotella Synthetic Blend in my diesel trucks and tractors and other synthetic blends in motorcycle, etc.

Not many people know that when there is a filter present it is better to use synthetic blend so I thought that might be useful information to people here. It is a bit counter-intuitive because we tend to think more is better.

Full synthetic is better than straight mineral oil in any engine that sits because they tend to have more issues with rust on metal surfaces and full synthetic is far superior in corrosion protection than non-synthetic. But synthetic blend is just as effective at protecting against rust as full synthetic.

Synthetic blend is a bit less expensive than full synthetic but you can't use the extended drain intervals to extremes that some people use with full synthetic because the base stock mineral oil has additive packages that wear out with heat and pressure faster than full synthetic oil loses it's lubrication properties.

At any rate, just passing on what I have learned from the airplane experience. If you want a clean engine with minimal wear and no corrosion then synthetic blend is the superior choice over non-synthetic or full synthetic.

In the rear end / differential / transfer case / gearboxes etc. still go full synthetic for the best protection when there is no filter. '

:thumb2
 
Interesting read, but why do the manufacturers spec full synthetics for their motorcycles ???
 
Very interesting read. Thanks for posting.:beerjug:
 
It gets worse :D straight grade oils suspend particles better than multigrade :thumb
 


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