Oil filter bypass valve

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Hi folks. Ran Mobil 1 5w30 with a Mobil 1 filter and currently running QSUD 5w30 with a fram ultra. When temperature is above 30 the oil light goes out about 1 second after engine starts. When temperature hits 20 and lower the oil light goes out when the engine is cranking. This happens with either oil and filter. Am I correct in assuming this is a function of the bypass valve. Never any noise
 
Originally Posted By: bullwinkle
Nope-the oil is thicker & builds up pressure more quickly.
Yes, because you get enough pressure to shut off the idiot light even at cranking speed.
 
To be a bit more detailed ...

The oil filter BP valve has nothing to do with the engine oil pressure sensor. However, the cold thick lube will have an effect on the overall engine oil system pressure and how it interacts with the pump BP relief. Pressure is the resistant to flow in hydraulics. The pump is a positive displacement system, the oil is going to move somewhere, somehow. So if you are getting pressure a few seconds sooner, it's because it's resisting flow and building up pressure sooner. That does not mean it's getting no flow, but it's likely getting a reduced flow, contrasted to a warm oil.

Don't panic though; it really does not matter. I've not seen any evidence that this topic actually matters in terms of wear-rate data. You don't have a lot of ability to control this. You can select a thinner lube (typically down one grade, if you want), but that, too, does not really affect wear in a discernible manner. If you're already at a 20 grade, there's not much room to go lower anyway.
 
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Originally Posted By: dnewton3
To be a bit more detailed ...

The oil filter BP valve has nothing to do with the engine oil pressure sensor. However, the cold thick lube will have an effect on the overall engine oil system pressure and how it interacts with the pump BP relief. Pressure is the resistant to flow in hydraulics. The pump is a positive displacement system, the oil is going to move somewhere, somehow. So if you are getting pressure a few seconds sooner, it's because it's resisting flow and building up pressure sooner. That does not mean it's getting no flow, but it's likely getting a reduced flow, contrasted to a warm oil.

Don't panic though; it really does not matter. I've not seen any evidence that this topic actually matters in terms of wear-rate data. You don't have a lot of ability to control this. You can select a thinner lube (typically down one grade, if you want), but that, too, does not really affect wear in a discernible manner. If you're already at a 20 grade, there's not much room to go lower anyway.
Thank you dnewton3 for the detailed info. With my 02 jeep with the 4.0 tractor engine with 170,000 miles I never worry about 5w30 HM every 5,000 its good. The mountaineer with the 4.0 with all the timming chains I watch it like a hawk. 68,000 miles
 
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