V6 engine. Does the oil sending unit line come from before the oil filter or after the oil filter? The reason I ask is I have been doing some reserch on oil filters and if the sending unit line comes from after the oil filter then there would be a change in Pressure. For example a Mobil Filter had #40 pounds going in and had #22 comming out. Then a Fram Filter had #40 pounds going into the filter and #38 pounds comming out.So if this line comes comes from after the oil filter then the person using the Fram Filter would have more Pressure on the Guage than the person using the Mobil Filter. If so then this could be the reason some people have more Oil Pressure than others. There was several Filters I just picked these two for example.
Don

All oil goes through the filter first after the oil pump, the pressure sender taps off after that. Keep in mind that our oil pressure guages are not precision calibrated. If the pressure drop across the filter is too high the oil will go through the bypass valve at the filter mount and skip the filter entirely.

JazzMan

Jazzman
I understand what you are saying, but my question is if I use a Fram Filter my oil pressure guage would read more than it would if I used the Mobil 1 Filter.
Don

Theoreticly, you're correct. Realisticly, you're probably correct too.

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Huh?

This is an issue I've found very frustrating... Engines with low oil pressure or wide swings in pressure have problems. At the very least it could be a sign the sender is headed south or there is some other electrical problem. (Never trust a dash gauge. Always use a known good mechanical job for testing work.) On the other end the engine has major wear or a marginal oil pump.

Mobil 1 has a very low pour temp and usually won't cause a bypass to open thru out most of North America. Crude based oils can start thickening quite a bit as high as 30F.

The Bypass Valve is in the block OE Fiero motors and any others using PF47 or PF52. Some motors have them in the filter. The bypass is usually set to open with about 7 PSI drop thru the filter media. To open the valve the oil has to be cold or the filter really dirty.

I'm not sure if more OP senders are between the filter and pump or after the filter. I think most are before the filter because a blocked filter/bypass or a bad pressure regulator could cause the filter to leak or even rupture. For that reason, you want to know if pressure in the filter can is too high. (Just a reminder... Oil flows into the filter can, thru the media, and out the center hole.)

Even if the sender is after the filter, Most oil pressure sender and guage sets don't have enough resolution to see a 7PSI change clearly if at all.

In either event I doubt sender position is the problem. The reality is that low OP means something is usually wrong... It can range from stuff getting worn out to internal leaks to a bad oil pump to a bad pressure regulator. I've long felt many of the responces to low oil pressure being normal or acceptable are people living in denial.

Oil pressure is regulated, usually by a blowoff valve in the oil pump. It should not change greatly durring engine operation.
Normal oil pressure for the L4 is listed as 36-41 PSI. The V6 is listed at 30-45 PSI.

A few PSI swing is one thing but when you see constant low pressure or big 20-25 PSI swings you need to look into it.

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No good ever came from dark and spooky. Norville "Shaggy" Rogers

The Ogre's Fiero Cave (It's also at the top of every forum page...)

quote Originally posted by ka4nkf: Jazzman I understand what you are saying, but my question is if I use a Fram Filter my oil pressure guage would read more than it would if I used the Mobil 1 Filter. Don

Is there a specific design difference in these two filters due to the use of synthetic versus dino oil?

Thanks guys for the reply.I read an article from Mobil that said that Mobil 1 flows more freely than reg oil and you might see a pressure drop when cold but will come back when hot. I do use Mobil 1 and think it is great.
Don