Here is a chart that goes to -20 C. At Bitog we discuss oils at operating at 8 to 16 cSt. Even at 0 F ( -18 C), a 0w40 would be at 1800 cSt, but probably not high enough to open the bypass. Would have the other oils opened the bypass? Maybe. This is why it drives me nuts when people say as long as it starts, it’s OK.
1. Yes, but the benefit will be quite small. Oil filters tend to bypass briefly after a cold start. This is a transient event that tends to only last while the oiling system is building up pressure, so generally not longer than a couple of seconds. The thicker the oil, the longer the bypass event will occur.
Hip shot. Increasing the chance depending upon temp and increased oil weight combo. Interesting chart.
Consider the case where oil pressure is only built up in the filter and in the oil passages between the pump and filter, and the passages downstream of the filter are still unpressurized. If the pump pressure rises to 60 psi, all of that pressure will be dropped across the oil filter and those short oil passages. If the filter makes up 50% of that total restriction, the dP across it will be 30 psi. It's as if the rest of the engine downstream of the filter doesn't exist yet.
Buzzkill. Why know when you can guess?
That's pretty much the purpose of it; yes.
Not true; it's not a "guarantee" by any long shot. Jim Allen's data shows your claim to be false. If the ADBV is doing its job, then there's pretty much no disparity in dP at startup; the transfer of pressure through the filter media is nearly instantaneous. Most certainly when the oil is warmed up, a dP BP event pretty much never happens. Only cold oils with moderate to heavy thickness cause a dP event at the media, and it's very short in duration (approx a second). For you to claim it's a "guarantee" would go against the real world data Jim collected and shared with BITOG.
I think your response shows that you have no idea how thick oil can be at start up if it is not up to the operating temperature.
In artic temps sure but for the vast majority of use it's not relevant. But at artic temps there's more going on like how much effort it takes to pull the oil through the pick-up tube and the effort to pump the oil.
Flow through the filter causes the dP across the bypass valve. Not oil pressure. If you had 100 PSI of oil pressure inside the filter and only 2 GPM of flow, the dP across the filter would be very low.
Yes, journal bearings "self-pump" flow through them ("draw the oil they need"), but there is also added flow due to the oil supply pressure feeding the bearings.
That would work, but the best way is to have an actual dP gauge across the filter. A plot of that dP would show a distance inflection in the dP when the BPV opened. There have been a few members here that have actually rigged up a dP gauge on their vehicle and collected "on the road" measurements of the dP across the filter. The threads are buried somewhere in this forum.
There's a recent big discussion about the LS oil pumps. The info shows that they are basically in pressure relief not far above idle, and the relief valve is essentially controlling the pressure throughout the engine RPM range. That explains why on GM engines with this oil pump, that a severally clogged oil filter could show a decrease in oil pressure, because the pump is basically always in pressure relief above ~1000 RPM.Here is an oil pump for a Chevy LS engine. The spring sits in the machined tube and determines the oil pressure the pump will put out by leaking some of the oil back to the sump.
Higher filter efficiency doesn't automatically mean less dP vs flow in an oil filter, or less volume getting to the engine. Ascents testing shows that high efficiency filters have pretty low dP vs flow curves. You only lose flow volume to the engine when the pump output flow decreases. All flow that gets sent into the engine flows through a "full flow' filter. Some may bypass the media if the bypass valve opens due to dP above the bypass setting.
