R. Gambino

I found this on the Experimental Aircraft Association 's website. It appears that the testing was done on an automobile engine. The debate is whether straight or multi-weight oil provides superior lubrication. http://www.eaa49.av.org/techart/str_oil.htm

Aeka GSR

iTrader: (4)

most wear happens at startup, so if it isnt a race only car I would use a multi weight.

neit_jnf

iTrader: (17)

Multi weight requires viscosity index modifiers to be able to perform at the rated weights, a 5W50 will have much more vi modifiers than a 20W50 and these modifiers burn leaving soot, ash and other deposits.

A straight weight oil is more "pure", to call it something, and tend to burn cleaner with less or nearly zero deposits.

I was actually thinking about using straight 40 or 50 full synthetic oil in my car during summer and then straight 30 or regular 10w30 during winter

Julian

iTrader: (14)

also full syns have stronger polymer strings, resulting in less degrdation of VI with shearing over time

homebrewer

I briefly scanned the article and saw the wear in question was related to CAMSHAFTS.

You can't compare a rotary engine to a pistone one. You can't compare a piston car engine to a piston airplane engine. Their operating environments are completely different.

IF YOU HAVE AN OIL QUESITON, POST IT ON WWW.BOBISTHEOILGUY.COM and don't ask a rotard.

R. Gambino

Evidently you scanned it too briefly, read the portion "SAE findings". This was not done on an aircraft engine

potatochobit

iTrader: (1)

im interested in heat tolerance more than super lubrication here in texas... lol

RX7LINK

iTrader: (3)

Don't use full synthetic oil because they don't burn, so you will leave deposits in your motor which can cause problem in the long run.

rynberg

Sorry, WRONG. Go to the back of the class....


The SAE study is very interesting.....but I'll just keep on using Mobil One 10w30....

Kento

That page on the SAE study, while interesting, overlooks some significant facts. The 10W30 "multigrade" oil was a Shell product that is a "Group III" oil. This means that although the manufacturer can claim that the product is indeed a "synthetic" oil, the reality is that the actual amount of "true" synthetic base stock used can be nearly 0%. The result is that they have to use far larger amounts of viscosity index improvers to keep the oil within its API 10W30 rating. The more viscosity index improvers used, the worse the oil performs when temps get nasty.

True full synthetics that are Group IV PAOs ("polyalphaolefin", like Mobil 1) or Group V (ester-based, like Motul and Royal Purple) don't need to use viscosity improvers, because the base stocks can be made to the specific viscosity needed (when making dino oil, you're trying to improve upon the base stock, which is a particular viscosity and often of varying grade).

The engine they used in the test was a diesel. Diesel oils have a different ratio with regards to additives, part of which is to combat the tremendous amount of soot deposits that quickly form in the oil. This probably robbed the multi-grades of even more stability-providing additives and/or base stock.

Aircraft engines are built for and run under entirely different conditions than an automobile engine. You really cannot compare the two.

potatochobit

iTrader: (1)

you must stay away from certain brand synthetics. if you want to run synthetic use a brand known to work good, like red line.

cewrx7r1

iTrader: (2)

What is the listed oil lubrications specs for this engine?

This is why I ask. It affects the outcome of this test.
The flow/protection value of 30 is the max value of the 10-30 multiweight, not it's most efficient part of the range. An the 10w is way lower than the 30.

If something like a 20-40 or 30-50 were available, they might do a lot better.

That's like saying the engine tolerances was designed for 30 straight wt. but we are testing also against 10 and 10-30. A rigged test unless we know more about the engine.

Kento

The purpose of the test was to determine whether a straight-weight or multi-grade oil protected against wear better. Thus, they only used oils within the viscosity of the 10W30, so one was straight 10W and the other straight 30W. And the wear test was measured on the cylinder walls, where flow rates that would make a difference in proper lubrication of bearings and other components with tight tolerances at low temperature extremes wouldn't really come into play (it should be noted that in that particular test, the straight 30W demonstrated less cylinder wall wear at extremely low temps as well as high temps).

It should also be noted that the instances of camshaft galling that the page talks about was with a Group III 15W50, which means it had a very high amount of viscosity index improvers to get that span between 15W and 50W. Full synthetic oils don't need VI additives to get that same range.

Drawing any conclusions from that linked page is like watching a movie in theatre through a pinhole seated in the first row-- you're not even close to seeing the big picture.