Whaleman

In May when I bought my 96 base I changed the oil with Mobile 1 and a Bosch oil filter. I just changed again after 3,500 miles ( I know I could go longer) again with Mobile 1 but this time with a Mobile 1 extended performance filter. M1-201A. Claims high efficiency and good for 1 year or 20,000 miles. While I don't have a digital oil pressure gauge I seem to notice a small decrease in oil pressure. Maybe 3-4 pounds. I know the analog gauge is not perfect. But after watching the oil pressure for 3500 miles I seem to see a very small decrease. Can different efficiency and different brands of filters affect the oil pressure a small amount? Thank You, Dan

DGXR

I suppose it's possible. Would not worry about it too much. Just be sure the filter gasket is sealed/no drips, the oil level is OK, and the oil pressure is in the normal range -- the general rule is 10 pounds per 1000 RPM but these engines typically have much stronger oil pressure... my LT1 is nearly always between 20-60psi according to the gauge.

I am more curious how you can tell 3-4 pound change in pressure on an 80-pound gauge... oil pressure will change with RPM, oil temperature, etc.

Purple92

While I think it's more than somewhat unlikely that a brand new oil filter is causing a pressure drop that is visible on the oil pressure gauge - I'm certainly NOT going to say it's not possible.

The factory equips all the SBC's with an oil filter bypass - it basically opens when the pressure drop across the filter is about 4 -5 psi. (Unfiltered oil is far better than NO oil !!!). If the filter were completely clogged - and assuming the oil filter bypass is working - the most drop you should see is about 5 psi, as that's where the bypass valve opens.

So ... what to do - if you're really convinced that you are seeing a pressure drop - you could pull the filter and put a replacement filter on (I'm a believer in the Mobil 1 filters - but the top of the line Wix / NAPA filters are also quite good, as are a number of others - e.g. Royal Purple, Amsoil, etc. I wouldn't even consider any filters made by FR**, and I'd avoid anything that is just too cheap). The $10 and the time it costs you is certainly annoying, but if you're like most of the others on this forum - we enjoy driving our cars, and if we're worried that the oil filter isn't filtering - we may not be enjoying things as much as we should - so from that perspective $10 is NOT a lot of money ... Or you could just leave it and check the oil ever few hundred miles - if the filter is really in full time bypass mode - I would expect that the oil should look "dirty" somewhat quicker.

Joe C

(my 2-cents, FWIW) -- question - do you have sufficient oil pressure with the mobil 1 filter? a couple PSI either way (dashboard indicated), IMO is nothing to worry about. to answer your question about the filter effecting pressure - i'd say most likely, but i'd also say it's probably insignificant. on my 85, my oil pressure (at idle) floats in a +/- 5 psi range. seems it's dependent on engine operating temperatures, idle speed, etc.. i really don't worry about minor variances in pressure. as long as your oil pressure is within the norm for a SBC, you should be good to go.

scotth48

I use the Ea filter from AMSOIL that is recommended with their Sinature Series oil for upto 25,000 mile oil change.

Whaleman

Thanks for all the responses. I do not think my perceived very small drop in pressure is a problem at all. I was just wondering if others saw small changes with different brands of filters. Thank You, Dan