Hey everyone,

Does the bypass valve open in an oil filter at high RPM's? If yes, what RPM? Are there aftermarket oil filters with no bypass valve?

I'm interested in what you guys have to say.

 

Damn i never thought of that. I would think they would have to still work until they are fully clogged, but even if it does bypass when you floor the pedal (which is not a good thing however considering i do it all the time), wouldnt you still like to have a bypass valve in case you forgot to change your oil and starved the engine when it clogged?

 

So you mean every time i floor it (about every time i go out) its not filtering the oil?

 

. There is more to this, it also protects your engine during a cold start when the oil is thick. Any amount of time the filter would be in bypass mode is minimal and not even worth thinking about.

 

If your oil pressure goes up then it is letting unfiltered oil through, it is something around 15 PSI of backpressure. On my chev, the oil pressure stays steady from 2k RPM to 5.5K RPM, so the filter is still filtering oil, so i bet you are still filtering your oil.

 

The by pass valve will open under higher than normal pressure.

Pressure depends on a lot of things like, oil viscosity, temperatures, dirt, engine RPM, pump pressure and volume etc.

So yes the vavle may open if at high RPM your pump delivers enough pressure to activate the valve.

Best way to prevent too high pressure is to make sure you have the right clean oil, clean filter, clean engine, warmed up and don't run at high RPM for too long.

The valve is a fail safe. Better to have dirty oil than no oil at all.

Good Luck,

Jim Henderson

 

Jim (or others) what do you consider high rpm on a 302? And what is optimal highway rpms for fuel efficiency/motor life? (1988 F150 302, AOD, 3.55 extended cab).
Thanks.

 

I don't know much about 302s other than they like to rev a bit. I am more of a big block guy(Dodge mostly and Ford) and those turn pretty slow, or I used to be pretty good with old ricers and those ran at 3,000+. I once ran an Olds small block at 4,000RPM/120mph for over 2 hours in desert heat and the engine loved it, me too.

I would guess if you kept above 6,000 RPM for a long time(several minutes) and if the filter was somewhat restricted due to dirt or tight filter media, then you might open the valve. This assumes your engine can handle high RPM to begin with. Also assumes your ear drums are already damaged beyond caring.

There are formulas that help you figure out the oil volume at RPM, but I am not sure where to look off hand. I usually stumble over those types. Last time I saw one was on the SHO website or an oil forum. Usually the bigger problem at RPM is that eventually the oil flow is insufficient to maintain bearing clearances and or all the oil is in the top of the engine and no longer getting back to the pickup fast enough.

I think the rule of thumb is clean oil, clean filter, normal driving, you should never have the valve pop open unless there is a mechanical obstruction.

There are so many variables as mentioned before that it is hard to say exactly what will open the valve. It is usually a combination of conditions and little of this and a little of that eventually adds up.

Wild guess for optimal engine life and efficiency is something between 2,000 and 2,500 rpm at 60mph. But all depends and optimal is in the eye of the beholder. Back in the 60s and 70s, V8s loved to run all day at near 3,000RPM. Now between 1,500 and 2,500 seems to be the norm but once again depends on what the designer was shooting for. My 460 4X4 with 4.10 gears runs a shade under 2,000 at 60mph if I recall. My chebby 350 with 3.08 gears runs at about 1600 at 60mph.

There are lots and lots of answers, all depends which one is right for you. Sorry I can't be more specific, like I said don't know your engine that well and all depends.

BTW, this is getting to be a philosophical discussion, there are very few wrong answers.

Good Luck,

Jim Henderson

 

Don't want to alarm anyone but I know for sure that at least some oil filter adapters (probably all ) also have bypass valves built in, and yes they will open at high rpm's if your engines' oil pump can develop enough pressure and volume.

 

BTW, the valve will almost always open on a cold start at below freezing temps with dino. The dino turns to almost like taffy at say the teens and the filter will open up just to minimize the back pressure of the oil until it warms enough to flow thru the filter medium instead of around.

I am pretty sure this happened when I drove a California car into temps that were in the teens or lower. I was using Valvoline 20W50 at the time, yeah I know too thick for sub freezing, but where the car lived almost never got below 30. My engine cranked really slow, the tranmission(90 W140 dino) felt like I was shifting thru fudge and the 50/50 mix of antifreeze was like a 7/11 slurpee. So I would bet the filter valve was open to save my engine.

But like before, under normal circumstances, you should be OK.

Just an opinion,

Jim Henderson

 

Your oil pump has a pressure relief spring valve body that limits the amount of oil pressure regardless of RPM. If it is set at 70 lbs max, it will usually give that at around 1500 rpm and not go any higher at more RPM's. This is with the newer Triton engines. The old FE blocks with stock pumps still have the same valve but the engine design is such that it leaks a lot of the oil at the internals. Getting the old engines to trip the valve didn't happen often. Regardless, the oil is being filtered as the system is designed.