A friend of mine has had problems with lagging oil pressure when
starting his 1977 MGB. He has access to one of those industrial oil
filter slitters that opens the filter like a giant can opener.
After having two separate oil pressure lags using Fram filters, he
slit open both filters and found the anti-drainback valves had failed
in both. These valves are simply a thin flexible membrane that
covers the filter inlet holes from the back side when there is no oil
pressure. In both filters, the membranes had developed a warp or
"fish mouth" around the edge that allowed oil to drain out of the
filter.
We have since slit open other filters by Unipart and Wix, and found
them to have a better design for the drainback valves. The Unipart
uses a metal cage to keep the valve from folding back, and the Wix
has the stoutest valve of all.
I am currently collecting some OEM Toyota filters to check them,
also. Toyota has started to change filter numbers like mad, and the
last filter I bought for my wife's Camry felt inferior to the one the
car came with (Japanese built). I've heard Toyota is now sourcing
their OEM filters here in the US to make them cheaper. Well, we'll
see about the quality when the old filter slitter goes to work...
Moral: All oil filters AREN'T created equal!
Cheers, PK
Paul D. Kile
kile_paul@aphub.aerojetpd.com
(916) 355-5162
GenCorp Aerojet
POB 13222
Dept 5784 Building 20019
Sacramento, California 95813-6000
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