Toobuilder
Well Known Member
With the results of the recent oil filter study now firmly under discussion, it feels like there is an emerging desire to branch out from even the traditional media filters and look to the auto/industrial world for “better”. While that is an admirable goal, it seems it’s a logical next step for that thread - this thread is the NEXT step beyond, so I thought I’d break off to keep that one on track.
Note: In this context, Bypass Filtration is the scheme where the oil pressure supply is tapped off and a small percentage of the oil is forced through an extremely fine filter media and returned, clean, directly to the crankcase. This oil filtration is too slow to feed the bearings directly, but eventually cleans all the oil in the sump.
Bypass filtration has an almost mythical reputation to actively purify oil while still in the crankcase. Its proponents will passionately argue the virtues of this scheme with religious fervor. On paper, it looks great - you run your crankcase oil through an incredibly fine filter that strips out every hard particle that can wedge in an oiled, sliding surface. And the dirtier the filter gets, the more effective it becomes. The heavy duty diesel truck and heavy equipment industry has many of the most vocal proponents, and since their big bore, large clearance, dirty fuel powerplants are a reasonable analog to our own, maybe it’s time to take a look. Since we know that extraordinary claims require extraordinary evidence, is anyone aware of any HARD DATA that would support widespread adoption of the bypass scheme on our engines? The primary benefit of the heavy mover crowd seems to be the vastly increased oil change intervals - in some cases, to indefinite. Many of these guys simply change the pressure filter and keep topping off the crankcase as required. One of the bypass filter manufacturers claims a life of 2000 (yes, two THOUSAND) hours before replacement is required. I am aware that bypass filtration is used on some airplanes - a buddy has a Franz system on his turbo Bonanza - but the standard oil change interval is maintained in his case.
So, anyone have any real data these systems work as claimed, and if so, does that open up any practical benefits for the Lycoming driver?
Note: In this context, Bypass Filtration is the scheme where the oil pressure supply is tapped off and a small percentage of the oil is forced through an extremely fine filter media and returned, clean, directly to the crankcase. This oil filtration is too slow to feed the bearings directly, but eventually cleans all the oil in the sump.
Bypass filtration has an almost mythical reputation to actively purify oil while still in the crankcase. Its proponents will passionately argue the virtues of this scheme with religious fervor. On paper, it looks great - you run your crankcase oil through an incredibly fine filter that strips out every hard particle that can wedge in an oiled, sliding surface. And the dirtier the filter gets, the more effective it becomes. The heavy duty diesel truck and heavy equipment industry has many of the most vocal proponents, and since their big bore, large clearance, dirty fuel powerplants are a reasonable analog to our own, maybe it’s time to take a look. Since we know that extraordinary claims require extraordinary evidence, is anyone aware of any HARD DATA that would support widespread adoption of the bypass scheme on our engines? The primary benefit of the heavy mover crowd seems to be the vastly increased oil change intervals - in some cases, to indefinite. Many of these guys simply change the pressure filter and keep topping off the crankcase as required. One of the bypass filter manufacturers claims a life of 2000 (yes, two THOUSAND) hours before replacement is required. I am aware that bypass filtration is used on some airplanes - a buddy has a Franz system on his turbo Bonanza - but the standard oil change interval is maintained in his case.
So, anyone have any real data these systems work as claimed, and if so, does that open up any practical benefits for the Lycoming driver?
Last edited: