If thick oil offers more protection, then isn't cold oil best?

[ZeeOSix]

Not disagreeing with this, but then how come we try to push the limits of OCIs? Why not change more often? New oil is clean oil, and a filter can't get the oil cleaner than draining out the dirty oil right out of the sump.

Shorter OCIs don't benefit as much with a high efficiency oil filter vs than a longer OCI does. The wear from dirty oil is proportional to the level of oil contamination and how many times the sump is pumped over and over through the engine. High capacity oil sumps also help in that regard (less sump circulation per mile). If the oil was always changed at 1000 miles or less on a broken-in engine, you wouldn't need much of an oil filter. Dumping the sump would be your "oil filter" so to speak. "Pushing longer OCIs" is all about other agendas, not keeping the oil cleaner. That's why a higher efficiency filter is better in those cases.

 

[Joba27n]

Joba27n: Thank You for this story!
There is quite a bit of unknowns in this story:
1) How many miles on the Engine
2) What were the previous OCI's like
3) What spec oil was used before the 20W-50 synthetic was put in.

Another thought here is, and it is a thought since I am not going to look the specs up, Ford did have the Coyote Motor use 5W-50 on some Track Package that they had. Ford did not spec a 20W-50 and I am willing to bet that the 5W-50 is not as thick.

There are members here that are using 0W-40 and 5W-40, 20W-50 is way too thick. JMO

I agree there are alot of missing links in the story and I honestly don't know the answer to any of the questions aside from previously 5W-20 was ran in the engine unless the owners son(my coworker) did the oil change. At which point he would run 5w-30 unless his old man was planning to tow. He would run 0w-40 if he was.

And that's interesting. It's been years since i've been on the floor at GM but I recall Camaro's (I think) specing 5w-30 for casual driving and a DexosR for track use. I forget but I believe DexosR was either 0w40 or 5W50... please fact check me

 

[facility1]

startup lubrication for say the first sec. or so does play a part in the engine wear, as well in the cold (winter) starts and the start/stop function,thats perhaps why the 0 grade in many oils are used and specified , plus good filtration and flow is a must in all situations, high loaded rpms & heat in the bearing and ring belt is a factor why decent anti-wear friction & modifier components (zinc compounds,moly,tiatinaium etc , etc) in the oil come into play, not only can a a higher viscosity oil over low viscosity oil can generate more heat as the thicker oil fights itself in its own friction (viscosity ) imposed to its self in resistance. viscosity modifiers can help in thicker oils for larger tolerances and flow but do shear down or thicken (heat oxidation and time ) into a less desirable lubricant ,that's also why a good base oil combination is required .

 

[Jetronic]

Reading comments here, it obviously comes up that thicker oil does a better job of separating two parts from contacting one another, which reduces wear. This is often stated as if "more is better" with no real cap on how thick is too thick until there are diminishing returns.

My thought (not my true belief) is this:

If thicker is always better until any circumstance, well, we know that a 5W-20 grade oil as say 5 degrees F is many times thicker than say a 5W-30 grade is at 212 degrees. Aside from the question of cold cranking, and assuming the oil pumps quickly enough to avoid damaging the engine since it is a 5W, then wouldn't a cold oil (that's still within temperature range for the grade) prevent wear the best, even better than nearly any oil at it's full operating temp?

A cold oil that's thicker will prevent wear better than a cold oil that's thinner, and a hot oil that's thicked will prevent wear better than a hot oil that's thinner. Moreover, a thick cold oil will generate more heat and activate it's additive package quicker.

I don't know what more to say about this.

 

[Jetronic]

Like most everything else here, isn't the answer now this black and white, and really more like "it depends on the relief valve in question"? If the relief valve is large enough to shunt off enough pressure, then wouldn't it remain cracked enough to maintain pretty good control of the pressure? I fully understand that in the SBC example, the relief value is insufficient to do that, but if anything the SBC example just shows that there are outliers and circumstances that create variation from powertrain to powertrain.

As with any spring, it takes more force to compress the bypass spring further (twice the force to double the compression) and in this case the force comes from pressure acting on the area of the valve. So to open the valve further you need significntly more pressure.

 

[ZeeOSix]

As with any spring, it takes more force to compress the bypass spring further (twice the force to double the compression) and in this case the force comes from pressure acting on the area of the valve. So to open the valve further you need significntly more pressure.

Exactly, and why a simple spring loaded pressure relief valve can't control the pump's max pressure output to an exact constant pressure level as the pump's volume output keeps increasing. The pressure and volume roll-off (seen in the Melling curves posted earlier) while the pump pressure relief valve is activated should be better (ie, meaning more roll-off gives a better "constant" pressure and volume control by the relief valve) with a PD pump that has less displacement per rev.