Blackstone Article on Viscosity

Status
Not open for further replies.
Joined
Jun 29, 2007
Messages
434
Location
Arizona, USA
Over at the Blackstone Labs site I found this article. Colored text is my emphasis:

Quote:


Engine owners often stray from manufacturers' recommendations regarding viscosity of oils. The engine builders dyno-test their engines using a specific viscosity oil, so when you use the viscosity they recommend, you are working with a known result. Going to another viscosity is an experiment, but it's usually a harmless one. For the sake of efficiency you want to run the lightest grade oil in your engine possible, within limits. We are seeing that trend for newer engines, for which the recommended grade is getting progressively lighter. The common 10W/30 has become a 5W/30, and some manufacturers even recommend 5W/20 oil. On the other hand, we can't see (in oil analysis) where it hurts anything to run heavier 10W/30s or even 10W/40s in modern automotive engines. The heavier oils provide more bearing film, and that's important at the lower end. If your oil is too light, the bearing metals can increase. If the oil is too heavy, the upper end metals can increase. The trick is to find the right viscosity for your particular engine, which is why we suggest following the manufacturer's recommendation.



Questions:
  • Any opinions / comments on this section of the article?
  • What does "upper end" and "lower end" refer to?
  • What are "bearing metals" in a UOA?
  • What are "upper end metals" in a UOA?
 
Or...
Top end is everything above the half way point of the connecting rod (wrist pin, piston walls, rings, valve train), and bottom end is everything below that point.

I think it hard to differentiate between crank bearing material and wrist pin bearing material. But then, Terry may set me straight.
 
The common usage of "top end" is the heads and above, including: valves, rockers, springs, camshafts and lifters (OHV engines have the lifters and the camshaft in the block but they are still normally refered to as "top end"). Therefore, the bottom end is the block and everything inside it, including: pistons, rings and pins, rods, crankshaft, oil pump, and the crank + rod bearings. Bearings can have lead and/or tin; upper end could be copper and/or bronze; pistons and rings could be chromium and/or aluminum.
 
I think the bottom is everything in a short block (chevy). Thats crank, pistons, con rods, camshaft

the top end is the heads and thier associated parts, valves, rocker arms, push rods, lifters.

The cam shaft and lifters kinda fall in the mid point of top and bottom end. you can group them with either, but it's usually the bottom. Cams need good lubrication. I have seen more cam lobes wear out on Chevys then any other problem.

Also the upper heads on push rod V-8's may have a different lube requirement then heads with single or dual cams on top.

The cylinder heads are usually the hottest part of the motor and it's where the oil breaks down the most. I see more varnish on cylinder heads then anywhere else on the motor. The bottom end can look bright and shiney, like new after 100,000 miles but the top will be a dark amber. (this is with aluminum block/head motorcycle engines., and aluminum head chevies. The air cooled motors show more discoloration then water cooled heads
 
Top end is cam shaft and all related valvetrain componets. Bottom end is usualy reffering mostly to crank,conecting, rod all associated bearings and the wrist pins. No one usualy worries too much about the pistons or rings directly since they tend to be happy and healthy if the other parts are hapy and healthy.

The main reason why I always count the cam in with the top end is two fold. 1) A lot of engines from the beginning of time all the way to today are OHC not OHV.2)The cam usualy mirror's the top end in term of oil preferance.
 
I wanted to add that their article is not a big deal in my mind. They are really just stateing the obvious. They are not saying that you can not try other viscosities they are just saying that you have no idea what the result will be. It is obvious that the OEM recomendation is going to be ok and well tested. The point of this site though is generaly to not settle for "ok" but to strive for excellence! So often going a bit thin or thicker then OEM recomendation is called for to get the best UOA.
 
Quote:


I wanted to add that their article is not a big deal in my mind. They are really just stateing the obvious. They are not saying that you can not try other viscosities they are just saying that you have no idea what the result will be. It is obvious that the OEM recomendation is going to be ok and well tested. The point of this site though is generaly to not settle for "ok" but to strive for excellence! So often going a bit thin or thicker then OEM recomendation is called for to get the best UOA.



My reason for posting this was because my Goldwing calls for a 10W-30 but I use a 40-weight here in Tucson. That's okay by Honda's own charts (40 okay in high temperatures). But I got to thinking about year-round. Come winter, my low might be 30 and my high 75. I could use a 10W-30 then. But I could also use a 10W-40 I would guess and be perfectly okay with it.
 
top end = piston+rings, bottom end = bearings, at least thats the way I see it. Never seen cams, rockers, or parts in the head increase wear from too thick an oil. Seen bearings wiped with too thin, and rings seal better with "correct" visc.
 
Status
Not open for further replies.
Back
Top