It was always my understanding that 20/50 started as 20w, then had modifiers added to behave different when heated.
Based on that premise, straight 50w ought to resist breakdown better than 20/50.

Not that it has much to do with the OP's original question.
But I think we already hit the oil thread button. LOL

I'm still trying to digest what rh8234 said. Not saying I doubt it,... but I haven't looked at it from that particular angle before.

 

20w50 and SAE 50 are the same viscosity when hot.

20w50 does not get as thick when it cools.

 

Ah right and wrong. Dino 20w50 is 20w more or less with modifiers that cause it to behave like a 50 when at op Temp. 20w50 Syn is a 50 w with modifiers that do not allow it to "thicken" as much when cold causing it to behave like a 20w when cold. All things being equal syn of the same w as a dino oil will flow easier when cold.
Back to the OP ? The experts seem to agree that 90% of engine wear happens at start up till the oil reaches its operating temp. That is why the search for the perfect multigrad oil. The life of engines have increased greatly in the last few decades in no small part due to the improved oils we have now.
I will not belabor the point. Your engine likely will not blow up, rather it will be subjected to much more wear than it would if you use a good 20w50 and a syn 20w50 is better yet. I would not use 50w if you paid me. If you use 1950s oil do not be surprised when you get 1950s engine life.


RAL

 

Yup; Air cooled aircraft engines have been using 60 and 70 wt. for years. And they do wear out.

 

True, and to complement, an SAE monograde oil of 30 is equal to a 65 aviation grade oil.

 

Yes, and Pratt and Whitney radials use 120 grade, which is 60 SAE. Back in the 50's, when I had my 1942 "45". Harley oil was rated the same. I use to use HD 120 in my old 45 in the summer, and 105 in cold weather. I don't know when they changed to SAE. It kicked over pretty hard even on the 105 grade when it got below 50 degrees. LOL

 

Does anyone know what Earl has to say about this ?
It is a complex theory , but really it can be explained and hss been explained in laymans terms for those of us who forget suck things from time to time.
Happy New Year to All @HDF.
Rob

 

 

Is there some problem with an oil thread here?

This is the oil section...nothing wrong with an oil thread in the oil section.

Any topic other than oil is off topic here...

 

Agreed.

Our comments are based on the history of the oil threads, which is kind of humerous to say the least. They have a personality of their own and our comments are meant in humor based on that.

No anger here. Just sarcasm.