0w40 to replace 5w20?

[ZeeOSix]

Where exactly is the oil pressure being read on the engine? On a Chevrolet LS engine the oil pressure is being read downstream of the oil filter, so a clogged filter would actually lower the indicated pressure. In real life, the bypass in the filter opens.

Not really. In that case, a loaded up oil filter (more restrictive) would not change the oil pressure down stream of the filter as long as the PD oil pump was not in pressure relief. If the same oil flow volume is going through the oil filter, then the same oil pressure after the filter will be read - oil viscosity being the same of course. The bypass valve opening in that case still wouldn't change the oil pressure down stream either, because the flow volume would still be the same if the pump still isn't in pressure relief.

Now if the oil pressure sensor was before the oil filter, then a more restrictive filter would make the oil pressure go up because the PD oil pump will be making more output oil pressure to push the same oil volume through the filter and oiling system.

 

[Snagglefoot]

Not really. In that case, a loaded up oil filter (more restrictive) would not change the oil pressure down stream of the filter as long as the PD oil pump was not in pressure relief. If the same oil flow volume is going through the oil filter, then the same oil pressure after the filter will be read - oil viscosity being the same of course. The bypass valve opening in that case still wouldn't change the oil pressure down stream either, because the flow volume would still be the same if the pump still isn't in pressure relief.

Now if the oil pressure sensor was before the oil filter, then a more restrictive filter would make the oil pressure go up because the PD oil pump will be making more output oil pressure to push the same oil volume through the filter and oiling system.

Yes, but PD pumps have a regulating spring in the pump and will send oil back to the pan as it regulates it. The oil pressure is not linear with RPM due to this regulating. You mention pressure relief. The pressure would be bled off at the pump if the pressure got too high and the oil filter would go into the bypass mode if it was almost plugged. The oil sensor on a LS engine would indicate low oil pressure when a filter was plugged and the pressure would come back if the filter went into the bypass mode.

Were are some LS engine Melling pumps with the spring shown.

 

[ZeeOSix]

Yes, but PD pumps have a regulating spring in the pump and will send oil back to the pan as it regulates it. The oil pressure is not linear with RPM due to this regulating.

With a healthy and efficient (ie, low "slip") PD oil pump, the volume and pressure output vs RPM is actually pretty linear, up until pressure relief of course. If the oil pump is worn or of ill design, it can have more "slip" than normal and the pressure vs RPM and flow output can roll off at higher RPM. Here's some actual flow vs RPM performance data. You can see how linear the curves are until they flatten off at pump relief. The stock LS pump is still linear up to ~6200 RPM, then falls off dramatically due to cavitation. Point is, the flow output vs RPM (and the corresponding pressure with the flow volume) certainly is basically linear with a well designed health PD oil pump.

You mention pressure relief. The pressure would be bled off at the pump if the pressure got too high and the oil filter would go into the bypass mode if it was almost plugged. The oil sensor on a LS engine would indicate low oil pressure when a filter was plugged and the pressure would come back if the filter went into the bypass mode.

The bold statement is still wrong. With the pressure sensor located after the oil filter, the oil pump will just put out higher output pressure to overcome the added resistance of the oil filter, and the pressure will remain the same at the location of the pressure sensor - if the pump isn't in pressure relief, then the volume hasn't changed, so the pressure can't change. As long as the pump stays out of pressure relief, the pressure after the filter will remain the same, at same RPM and oil viscosity of course, because the flow hasn't changed - the pump is not in pressure relief and therefore not sending oil back to the sump or back to the input side of the pump (depending on design).

And even if the filter goes in to bypass before the pump goes in to pressure relief, the oil flow volume going past the pressure sensor location will still be the same, so the pressure will also remain the same if the filter bypasses. Volume going through the filter and in to the engine is only reduced when the pump hits pressure relief, regardless of what else is going on.

 

[Al]

I put the 5W-40 in my '22 Forester that calls for 0W-20.

 

[SubieRubyRoo]

After reading around, I *think* I know what everyone will say.

I have 12 gallons of M1 FS 0w40 that I acquired. Ive read the positive opinions and about it's cleaning ability. I'm currently running it in my '11 Ram 5.7l. The Dodge forums seem to have a lot of people running 0w/5w40 in their 5.7l Hemi engines with the reasoning behind it is that that 6.2l/6.4l spec it. Engine seems to run fine, possibly a little quieter. I do from time to time get a code for incorrect oil viscosity, but it does not throw a CEL or disable MDS.

I was considering using it in my 3.7l Liberty which although has low mileage, I know for a fact that it didn't necessarily have the best care before I picked it up. That engine calls for 5w20. I've been running 5w30 in it. Any reason not to use the M1 0w40 other than a possible decrease in fuel economy?

Use it, or PM me for my address so that I can

 

[Snagglefoot]

With a healthy and efficient (ie, low "slip") PD oil pump, the volume and pressure output vs RPM is actually pretty linear, up until pressure relief of course. If the oil pump is worn or of ill design, it can have more "slip" than normal and the pressure vs RPM and flow output can roll off at higher RPM. Here's some actual flow vs RPM performance data. You can see how linear the curves are until they flatten off at pump relief. The stock LS pump is still linear up to ~6200 RPM, then falls off dramatically due to cavitation. Point is, the flow output vs RPM (and the corresponding pressure with the flow volume) certainly is basically linear with a well designed health PD oil pump.

View attachment 165977


The bold statement is still wrong. With the pressure sensor located after the oil filter, the oil pump will just put out higher output pressure to overcome the added resistance of the oil filter, and the pressure will remain the same at the location of the pressure sensor - if the pump isn't in pressure relief, then the volume hasn't changed, so the pressure can't change. As long as the pump stays out of pressure relief, the pressure after the filter will remain the same, at same RPM and oil viscosity of course, because the flow hasn't changed - the pump is not in pressure relief and therefore not sending oil back to the sump or back to the input side of the pump (depending on design).

And even if the filter goes in to bypass before the pump goes in to pressure relief, the oil flow volume going past the pressure sensor location will still be the same, so the pressure will also remain the same if the filter bypasses. Volume going through the filter and in to the engine is only reduced when the pump hits pressure relief, regardless of what else is going on.

With a healthy and efficient (ie, low "slip") PD oil pump, the volume and pressure output vs RPM is actually pretty linear, up until pressure relief of course. If the oil pump is worn or of ill design, it can have more "slip" than normal and the pressure vs RPM and flow output can roll off at higher RPM. Here's some actual flow vs RPM performance data. You can see how linear the curves are until they flatten off at pump relief. The stock LS pump is still linear up to ~6200 RPM, then falls off dramatically due to cavitation. Point is, the flow output vs RPM (and the corresponding pressure with the flow volume) certainly is basically linear with a well designed health PD oil pump.

View attachment 165977


The bold statement is still wrong. With the pressure sensor located after the oil filter, the oil pump will just put out higher output pressure to overcome the added resistance of the oil filter, and the pressure will remain the same at the location of the pressure sensor - if the pump isn't in pressure relief, then the volume hasn't changed, so the pressure can't change. As long as the pump stays out of pressure relief, the pressure after the filter will remain the same, at same RPM and oil viscosity of course, because the flow hasn't changed - the pump is not in pressure relief and therefore not sending oil back to the sump or back to the input side of the pump (depending on design).

And even if the filter goes in to bypass before the pump goes in to pressure relief, the oil flow volume going past the pressure sensor location will still be the same, so the pressure will also remain the same if the filter bypasses. Volume going through the filter and in to the engine is only reduced when the pump hits pressure relief, regardless of what else is going on.

Sorry Zee. Going to have to end it there. We can agree to disagree. Snag.

 

[ZeeOSix]

... Look into PD oil pump operation some more. Key thing to remember is the only time oil flow is reduced from a PD oil pump is when the pump goes into pressure relief.

A pressure sensor located after the oil filter will always read the same pressure at the same oil volume flow and viscosity, regardless of the filter resistance as long as the pump isn't in relief. If the oil pressure sensor is before the filter (which is usually not the case), then a clogged filter would actually make the indicated oil pressure increase until the pump hit pressure relief.

 

[1BadManVan]

No problems at all running ESP 0w30 or 5w30 in my 2016 3.6L Wrangler. I've been running it for years now.

Different version of the 3.6 compared to him, could be the difference

 

[AmBeRnEcTaR]

If that were my HEMI, I'd make a smaller move initially - to 0w30. If that fares real well in both sound and performance, then move to 0w40 next summer.

That's exactly the same reasoning I used with my lowish mile 2014 Wrangler Sport 3.6L.
5W-20 as spec'd for the first few years, latest oil change was Mobil 1 AFE 0W-30.
All Quiet on the Western Front

 

[BigTimeTA]

It's fine as long as you can get back to 5W-20 as soon as possible. Even if you want to keep using 0W-40, no significant fuel consumption to worry about. I'd use 0W-40.

 

[demarpaint]

Different version of the 3.6 compared to him, could be the difference

Seems odd, I know a lot of people with the PUG upgrades running 0W30 and 5W30 with no problems. I also frequent Jeep forums and haven't seen any complaints running the thicker oils.

 

[1BadManVan]

Seems odd, I know a lot of people with the PUG upgrades running 0W30 and 5W30 with no problems. I also frequent Jeep forums and haven't seen any complaints running the thicker oils.

I agree it shouldn't cause any issues, it could be a fluke that it was completely unrelated as well. We have an extended warranty on our 2019 wrangler so I just use the best off the shelf oil 0w20 and so far, very smooth and quiet. I also ran 5w20 in my 2012 caravan for 7 years and traded it in with 220k on the motor without any issues and I beat the crap out of that thing lol