Does the bypass relief valve pressure matter much?

[ZeeOSix]

True, but oil doesn't need to be all that thick for an oil pump to be in pressure relief at cold idle. On typical engine, the oil pump may be bypassing on cold start with room temperature oil. In any case, I was mostly concerned with colder starts when oil pressure buildup is more critical, at temperatures where any oil pump will be bypassing.

On all the vehicles I've owned that have actual oil pressure gauges, the oil pressure on cold start-up and at idle was pretty far below what the oil pump pressure relief was set to. Now if you revved the engine up pretty high right after a very cold start-up then you could get the oil pump to hit pressure relief.

I would say it's not "typical" for an oil pump to hit pressure relief on a cold start-up with "room temperature" oil, unless you're really revving up the engine. Room temperature implies 68-70F.

I don't think oil pressure will take much if any longer to build on a very cold start-up unless the wrong oil "W" rating is used, and the pump actually has problems with the pumpability of the oil. The oiling system should remain full of oil unless the filter's ADBV is not working correctly, so as soon as the pump is turning, it's moving oil and sending oil to the oiling system.

 

[bullwinkle]

I’m sure filter ballooning with a blocked bypass was a bigger issue back in the day with thick conventional oil & cold temps. Can’t believe a thin synthetic could even do that.

 

[oil pan 4]

Even in that case, it still depends on what the oil volume and viscosity is going through the oil filter (and how loaded the filter is) if those conditions put the filter in bypass or not. The filter's bypass operation, and the oil pump pressure relief operation are caused by independent factors ... they are not connected.

Yeah they are 100% connected. If the oil pump has a 90psi relief valve it's going to push more oil across the filter and through the engine than say a pump with a 50psi relief.

 

[ZeeOSix]

Yeah they are 100% connected. If the oil pump has a 90psi relief valve it's going to push more oil across the filter and through the engine than say a pump with a 50psi relief.

That's true, but that's the only "connection". My point is that the filter's bypass valve operates independently from the pump's pressure relief valve. A filter could go into bypass before the pump hits pressure relief, or the filter may not, even if the pump is in pressure relief... it depends on many factors.

 

[Soft Cars]

I've heard that some cars have the bypass valve built into the part where the oil filter mounts to.

 

[ZeeOSix]

I've heard that some cars have the bypass valve built into the part where the oil filter mounts to.

Lots of older GM engines have a built-in filter bypass valve. Also, some engines with a cartridge filter have it built into the engine or the cap that screws onto the filter hole.

 

[Soft Cars]

Lots of older GM engines have a built-in filter bypass valve.

Do you know if the GM 3800 V6 has that?

 

[ZeeOSix]

Do you know if the GM 3800 V6 has that?

Do the specified oil filters for it have a bypass valve? If not, then it's built into the engine.

 

[oil pan 4]

I've heard that some cars have the bypass valve built into the part where the oil filter mounts to.

I think most do. That way when someone takes their car to the $20 oil change place and they put the wrong filter on the car, say one that fits but with no bypass that way it doesn't crush the filter when car cold starts with a dirty filter later on.

 

[oil pan 4]

Do you know if the GM 3800 V6 has that?

Other gm products I tore apart all did. Never had to go into a 3800 series 2 that deeply. I would be surprised if it didn't.

 

[oil pan 4]

Do the specified oil filters for it have a bypass valve? If not, then it's built into the engine.

Gm engines usually have a built in bypass and call for a filter with a bypass.

 

[Sayjac]

Do you know if the GM 3800 V6 has that?

3.8L engine used on many older GM vehicles. A quick google shows ACD PF47 common filter for those, and cross to 3387a filter, no bypass listed on filter data sheet. Must have block bypass there. To confirm, I'd enter specific 3.8L GM vehicle in a filter look up. See no bypass, then on engine/block. Many older GM have block bypass, but some newer GM still use it too.

As for topic, I've never been very concerned about bypass psi spec. As long as reputable filter company shows filter as correct application, good to go for me.

 

[ka9mnx]

Why I use OEM filters...

 

[ZeeOSix]

Gm engines usually have a built in bypass and call for a filter with a bypass.

Not the ones I've owned or seen. For instance, my Z06's oil filter did not have a bypass valve.

 

[oil pan 4]

As noted by others the media construction & Holding capacity is two of the primary determinants of what bypass PSI will be.

Yes cellulose will have higher pressure differential vs glass and other synthetics will be lower.
For example paper hydraulic filter and glass media hydraulic filter of similar size and similar filtration the glass filter will be rated 50% to 100% more and the glass will have better micron numbers.
Draw backs are the glass filter will cost 50% to 100% more....

 

[oil pan 4]

Not the ones I've owned or seen. For instance, my Z06's oil filter did not have a bypass valve.

I only work on poor people cars so I wouldn't know about zo6.
That's good because I say it's better to use the bypass at the top of the filter head rather than the bypass in the bottom of the filter where all the dirt collects as most filter screw on vertically.

 

[ZeeOSix]

I only work on poor people cars so I wouldn't know about zo6.

The whole LS series of GM engines for many years had the filter bypass valve in the block.

Exactly which GM engines specify an oil filter with a bypass valve when the engine also has a filter bypass valve in the block, like you mentioned in post #31?

That's good because I say it's better to use the bypass at the top of the filter head rather than the bypass in the bottom of the filter where all the dirt collects as most filter screw on vertically.

If an oil filter with a bypass valve in the dome end was put on a GM engine that has a filter bypass valve in the block, then it's possible that the "good" you mention could be defeated.

 

[oil pan 4]

The whole LS series of GM engines for many years had the filter bypass valve in the block.

Exactly which GM engines specify an oil filter with a bypass valve when the engine also has a filter bypass valve in the block, like you mentioned in post #31?


If an oil filter with a bypass valve in the dome end was put on a GM engine that has a filter bypass valve in the block, then it's possible that the "good" you mention could be defeated.

That seems to be what GM does.
Some of the older engines seemed to have very weak bypass springs. I wouldn't recommend closing them off.
The old small block, big block and 6.2/6.5 engines would always have a bypass in the block and in the filters I would get. I will have to check if the Detroit filters have a bypass I don think they did.

 

[ZeeOSix]

That seems to be what GM does.
Some of the older engines seemed to have very weak bypass springs. I wouldn't recommend closing them off.
The old small block, big block and 6.2/6.5 engines would always have a bypass in the block and in the filters I would get. I will have to check if the Detroit filters have a bypass I don think they did.

If the GM engines you described having only a 3 to 5 PSI filter bypass in the block also used an oil filter with a bypass valve set to 8 to 12 PSI, then obviously the built-in block bypass is going to be wide open way before the filter bypass valve even cracks open. Doesn't seem logical to me for GM to specify a filter bypass in both the block and the filter.

 

[Snagglefoot]

I’m sure filter ballooning with a blocked bypass was a bigger issue back in the day with thick conventional oil & cold temps. Can’t believe a thin synthetic could even do that.

For sure, but let’s ask Anton Parr. A “ thin synthetic” in a 0w30 has a kinematic viscosity of around 9-10 at 100 C, but during a cold start at freezing conditions that same 0w30 has a kinematic viscosity of 550. I have no idea of how well that oil goes through the oil filter.