Originally Posted By: mene
Originally Posted By: turtlevette
Originally Posted By: jrustles
Originally Posted By: Wolf359
As most wear occurs at start up which is below operating temperature, you're going to wear the engine down quicker using a thicker than recommended oil.
Whoa. Guys, can we stop with this stuff? Statements like these are just incomprehensive and abstract and need to stop.
Oil does not deactivate when it's cold, only to later prevent wear when it warms up to 90C. That's definitely not how it works. Interestingly, some EP additives exhibit this behavior, and they don't care what VI of oil they're in.
Also, please please understand, start ups won't kill an engine. To be facetious, how many engines have you seen mechanically fail from wear caused by too many startups?
This 'start up wear' bit is IMO an undying marketing gimmick.
Let's look at two of the most common misperceptions surrounding 'start up wear'
-
the sliding engine parts instantly begin to wear as badly as dry parts until oil pressure is achieved
this is true if all the motor oil instantly teleports to the pan everytime the engine is shut off.
Needless to say, that's not true. Oil and it's additives remain stuck to parts. This is partly an inherent quality of the oil (polarity, surface tension) and modified behavior with additives. The thin film left on parts and any residual oil in the gallery alone are plenty of boundary lubrication (the base oil itself also acts as boundary/mixed in this instance) to see the parts through a few cycles until more oil arrives at their respective outlets. IRONICALLY, more polar base oils and [the evil]
higher viscosity oils leave a meatier film on parts. Further to that, barring severe pumpability restrictions ie. excessively high CCS viscosity, the coveted oil pressure can often be seen to build
faster
-
viscous motor oil flows with more resistance throughout the oiling system, relative to lower viscosities, therefore the parts are not getting their "full" flow and are thus wearing faster
Simply not true. Flow does NOT equal lubrication, and apart from a localised cooling effect at high temperatures, has otherwise NO BEARING (no pun
) on the oil's ability to lubricate. Ah yes, there was a caveat in that last sentence- cooling effect. Luckily that's not a concern during
start up Nevertheless, we're discussing differences which may be imperceptible anwhere outside of a lab. 0w20 vs 10w30? Yeah, not going to notice any fuel economy hit above freezing. Not just because the practical differences in viscosity at 70Fahrenheit for instance regarding fuel consumption or wearing an engine are imperceptible and non-existent, respectively, but also because of the following bit :
regarding the abstract nature of the misconceptions, it is believed that an engine warming up with a lower viscosity, high VI oil wastes less fuel. At the same time, the belief is held that oil additives perform less optimally until NOT (normal operating temperature).
Further, its a fact that an engine operating below it''s NOT is operating in a richer fuel trim, thus using more fuel.
One other fact that many people overlook is that the resistance (molecular friction) that a lower VI/higher visc. oil 'puts up' against pumping and shearing (including windage) costs energy, indeed, but it's not a robbery!! The kinetic energy taken in, is simply outputted as heat directly into the oil. And that, my friends, is the purpose of warmup. Theoretically, the engine running the lower VI/higher visc oil reaches NOT sooner, thus the fuel trim normalizes sooner, and temp. activated additives become fully effective, sooner. And now that it's all nice and toasty at NOT, it's got the ~same KV as the higher VI oil
The difference is it theoretically got there sooner. Again, the difference? barely noticeable, but thems the facts.
Oh yeah, 10w30 of the same product lines will usually have less polymer, PPD to varnish your ringpack over time, so that's a nice bonus on top of VI being
completely useless in any tropical environment.
You get an F on all that stuff above. Thick oil does not properly lubricate the rings. Think of it as the ring scrapes the oil completely off the cylinder when it's thick instead of riding on the oil film. Like a squeegee scrapes water off glass.
I guess you could do an experiment to prove it to yourself. Put a straight 70wt oil in your engine and remove the thermostat. Run the dog out of it then let us know how many miles you get before it starts smoking. You'll get a lot but not 300K miles.
You could try pure Lucas additive. It's pretty thick. You'd like that.
10W-outdated.
Hmmmmmm.... I ran the old van with Mobil 1 5W50 for 300K+ miles after buying it with 140K only the last 30K I tried a 30 weight oil which it didn't like much the car went to the junkyard with a cracked unibody with over 170PSI in all cylinders and burning 1Qt. 2700 miles when using the 30 oil. So, thick oil will wear an engine specially the rings, right....
The trend has been for lighter weight oils since the late 80s. You have manufs recommending 0W-20 now. The Toyota 0W-20 is a very light oil and they're getting ready to come out with the 0W-16 oil.
You best start writing letters telling them they're all full of it. I'm good though. Most people here have already told me I'm full of it. Thanks all.
