Mobil 1 Filters?

[Dually]

I generally use Jomar (non bypass), Wix Racing (non bypass) Baldwin or Ford Racing Filters. Amazing the difference in filters when you take them apart. Change oil every 1000 miles and filter every 500 miles. Like to open filter every 500 miles to see whats going on in engine.

An obvious question is does the Mobil 1 filter have an anti drainback valve or check valve? Mobil 1 sites states they only put check valves in filters that the OE requires has same. I have used the mobil M1-301 on a SBF but never the one you noted. Cannot even find it on the Mobil 1 site when I try to located under a SBF.

If no check valve or anti drain back valve the level of oil in filter will drain down until oil can no longer return to the engine through the supply hole from the pump. This will allow oil filter on a SBF to drain down about 2/3 of the way when engine if left after running due to fact filter on side and angled slighly downward. Drainback valve is generally a rubber flapper that can be seen through the inlet holes which are the holes on the outside of the mounting area. Keeps oil filter full so engine does not run dry during initial startup. Will show oil above full if engine sits after running.

I think this may be your issue.

PS: Mobil 1 filters are a great product. Used exclusively with their synthetic oil on a forged stroker 383 LT1 that we ran as hard as you can run an engine. Pulled it apart as general maintanence after 500 hard hours of use in marine environment and the engine was perfect.