Is Mobil 1 0w-40 too thin?

[johnmyster]

Im glad there are members like you who corrects our mistakes.

Would you also say thicker oil does not increase the pressure? Because I am also under the impression that if it does, and there was this dude called Bernoulli that might have found a negative relationship between a fluid's speed and pressure

Seriously though, I am a mechanical engineer, and I am quite surprised how factually wrong a significant amount of comments on this forum. I used to believe older members with more posts might have been better educated, but I am seeing that there is an echo chamber effect going on with misinformation

I’m pretty sure you’re the one that dug up a salient call on misinformation in an otherwise dead thread.

What state is your PE in?

Bernoulli doesn’t apply, so perhaps go back over your EMCH341 Fluid Dynamics notes. You’re comparing two different fluids in an open system and not one fluid at two points in a closed system. Pressure relief valve and pump slip are all you need to know.

On one hand, BITOG believes thick oil puts more heat into any given system and gets up to temperature faster. On the other hand, without suitable reference data, BITOG believes the specific heat of seven pounds of thicker oil is so much higher that it markedly delays engine heating. In either case, BITOG can’t realize the myriad of other (larger) variables that have greater impact.

Sorry BITOG isn’t the theoretical echo chamber you’d like it to be.

 

[kschachn]

Did you take the time to go through my older posts. I feel important now.

And yes, viscosity of any oil, including monograde, can change permanently with heat and mechanical stress. I think the former is easier to understand so lets focus on that. There are 3 mechanisms i can think of, oxidation, thermal cracking, and volatilization, the second one decreasing the viscosity while the first and the last one increasing. Volatilization it was more a deal back in Base 1 oil days. I am not 100% sure of this, but I think volatilization does not have a significant impact in any engine oil you would buy today, beyond the secondary effects through the shorter carbon chains created by the former mechanism. Its been decade since I last learned about these things though. Probably chatgpt could answer your questions better on this. But thermal cracking is also how refiniers break longer chains into smaller ones.

But i am not sure what is the issue there. Do you think you could run a monograde oil forever without any change in viscosity?

Oh heavens don’t feel special on my account. I didn’t go through your older posts, I just recalled the ones we exchanged. I have no idea how many others there are where you claimed that.

 

[ZeeOSix]

That’s true for an ideal PD pump before the relief valve opens — it displaces about the same volume per rev regardless of grade with thin oil having a little more slip.

Not sure exactly what engine is being discussed, and not going to read from post 1. With a traditional PD oil pump with a spring loaded pressure relief valve, the pump volume output and hence the oil pressure will still keep climbing at some rate even while the pump is in relief. How fast it rises depends on the design of the pump and how well the PRV operates and flows. With all these newer ECU controlled variable output PD pumps (and some are even just spring loaded variable control without the ECU), how well they control to a constant oil pressure all depends on the exact design of the control system.

About "pump slip" ... once the pump is in any level of pressure relief then pump slip isn't really a factor anymore because the pump is cutting back flow regardless of how much pump slip is going on. Pump slip would only matter if the PRV is totally closed. Example would be a worn out pump that can't make enough flow and pressure at idle or low RPM because it's so worn out that the pump slip is way too much. A healthy PD pump isn't going to have much pump slip even with hot oil ... usually it will be around 15%. But PD pumps are typically way over designed in terms of volume output per rev, so that 15% slip is basically moot unless the pump is really in bad shape. Oil pumps on GM LS engines (spring loaded PRV design) actually start going into pressure relief as low as 2500 RPM with hot oil.

If an oil pump is designed right and in good condition, it's going to provide adequate flow with a wide range of oil viscosity. If it didn't, engines like the Ford Coyote (and similar engines) wouldn't specify viscosity anywhere from 5W-20 to 5W-50. Look at some of the OMs that show a huge range of oil viscosity. If the pump couldn't still provide adequate lubrication over that huge range of oil viscosity, they would't be called out in the OM.

 

[thastinger]

This is a follow up post to a post I made earlier and mistakingly put in the PCMO section. I have a ‘19 GLI (2.0T MQB) with an E85 tune. Car is spec’d for 0w20, I typically run a 504 spec 0w30. Most over there suggested what I was thinking, jump to a 40w oil to combat fuel dilution with E85. My first thought was M1 Euro 0w40, cheap and easy to find at Walmart. However in research, I’m seeing that this specific oil is known to be on the thin side of a 40w, nearly a 30w (please correct me if needed)

With that in mind, should I look a different route? Maybe the 5w40 version, or a Castrol Euro 5w40? I’m not super versed on reading a VOA to notice exact differences but I’m learning!

Are you running E85 year around? As a DD?
I would be looking at a 10-30/40 if that was the plan.
I run E85 in one of my vehicles but only when I race it, it is on 93 otherwise. I don't have a flex tune or a % sensor so I drain the tank to make the switch. I choose not to run E85 all the time because there are only a couple of pumps in the area and I would need to make sure it was at least E80 every time. I just keep a couple of 55 gal drums, take a bunch of 5 gal cans to the pump and test when I get them home, if they test 80+ they go in the drums, if not they go in the Wife's flex fuel vehicle.

 

[ZeeOSix]

And to add, choosing the correct W grade oil for cold starts is way more important for "cold flow" than anything else. The W grades were invented and J300 tweaked to ensure engines don't destroy themselves from lack of lubrication if an adequate W grade is used.

Choose a KV100/HTHS viscosity based on hot running conditions and engine use. As discussed a million times here, higher KV100/HTHS viscosity is going to provide more film thickness between moving parts and therefore give more wear protection (basic Tribology). All grades of oil when at operating temperature are going to pump and flow probably more than the engine really needs. Oiling systems are typically over designed. No smart engineer with a robust testing program of the design is going to put out an oiling system that operates "on the edge" and risks possible engine damage.

 

[thastinger]

Roughly 72-74

Are you running "true" E85 fuel OR E85 out of the local gas station? Big difference in % ethanol.

Guess I'm lucky. Local Harris Teeter has always tested 82-83 here, it is all I run but I don't stay on E85 all the time.

 

[altaylar]

Folks you all are right. I did not know what i was talking about but now learned a lot. Thick oil creates more heat, so warms up even faster. Since pretty much all oil pumps we have here are PD, its flow rate is constant, and oil thickness has absolutely no differential effect on flow rate at high surface to volume areas (low clearance) vs wide pipes. And most importantly, regardless of how thick of an oil you use, your bypass valve will have ignorable effect in your oil flow.

Now that we have cleared this thread from my ignorance, please. Lets go back to the OP's topic.

 

[ZeeOSix]

Thick oil creates more heat, so warms up even faster.

Not enough to really matter, especially on an engine that has a coolant-to-oil heat exchanger. Also, people claim that thinner oil "cools parts better because it flows better", but again the difference is so small it really doesn't matter in the whole scheme of oil viscosity. Choosing an oil viscosity shouldn't be based on if it warms up faster or cools better because those factors are small and don't really matter compared to the other aspects of what viscosity does which is providing a film thickness between moving parts to prevent wear. If thinner oil cooled so much better and that was a big advantage, then manufacturers wouldn't be specifying a thicker oil for track use. They spec a thicker oil because it has more viscosity at higher temperature than a thinner oil does, regardless of how well the thinner oil "cools parts".

Since pretty much all oil pumps we have here are PD, its flow rate is constant, and oil thickness has absolutely no differential effect on flow rate at high surface to volume areas (low clearance) vs wide pipes. And most importantly, regardless of how thick of an oil you use, your bypass valve will have ignorable effect in your oil flow.

Thicker oil will make the pump hit relief a bit sooner and go into relief farther than thinner oil, which will cut back some output flow to the engine. But even so, the pump is still going to put out more flow volume than the engine really needs if the pump was designed and sized right to match the oiling system. Owner's manuals wouldn't call out a big range of oil viscosity between xW-20 and xW-50 if the pump couldn't provide adequate flow to the oiling system over that big viscosity range. As mentioned earlier, choosing the right W grade is important for cold start flow and lubrication. If the pump and oiling system can operate right and lubricate the engine with enough oil volume with the right W grade then it's also going to operate right with any KV100.