I know that the CarQuest and MicroGuard oil filters are considered two of the best oil filters on this forum. I understand that both are rated for 99% efficiency at 20 microns. First, is there any difference between the two filters or are they exactly the same other than the name printed on them (i.e are they constructed exactly the same with the exact same internals)? Second, I was wondering if anyone has any data on the flow rate of these two filters? The 99% efficiency sounds great but if they don't flow as good as a less effecient oil filter, you could be starving your engine of oil periodically. In other words, you can make a filter that is 99% effecient at 5 microns, but the flow rate would probably be way too slow for a engine to survive. I'm just wondering if they flow comparable to other less efficient oil filters or does the 20 micron rating cause a slow down in oil flow? Third, are there any other brands of oil filters that offer the same filtration efficiency to the CarQuest and MicroGuard filters?
Carquest and MicroGuard oil filters
- Thread starter BradleyB
- Start date
They're exactly the same, made in the same factories (usually made in Viet Nam).
Filters don't have flow rate. And it doesn't matter because your oil pump is positive displacement.
https://bobistheoilguy.com/forums/threads/the-myth-of-flow-over-efficiency.398959/post-7343928
Filters don't have flow rate. And it doesn't matter because your oil pump is positive displacement.
https://bobistheoilguy.com/forums/threads/the-myth-of-flow-over-efficiency.398959/post-7343928
BrendanC
$100 site donor 2024
please read before posting. this just scares other people. these filters are not restricting oil flow. no other OTS filter currently can match the carquest premium/microguard/premium guard EX filtering efficiency. you may be able to find a fleetguard or donaldson but chances are they don’t offer it for your application.
The mantra of "flow over efficiency" is a myth. @Hohn beat me to posting the thread in post 2 above showing why. None of the filters compared in that thread ever made an engine fail because they were "too flow restrictive".
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That thread will be (and should be) reposted here many, many times because the idea that filter restriction matters to oil pump flow is one of the most pervasive (and wrong) misunderstandings around. It might be your "legacy thread" that lives on long into the future. I know of linked it to other areas well outside of BITOG on many occasions.
You'd be surprised how many engineers believe the myth because their concept of flow can't account for a PD pump.
It's like trying to learn electronics by thinking of constant current and variable voltage drop. It's just completely counterintuitive to so many people.
The only exception I can think of is the GM LS engines, which didn’t have the greatest oil pressure new, and have issues with the pickup oring and seem to wear out oil pumps & bearings somewhat at high mileage. The company has a somewhat overworked ‘19 Express with the 6.0 LQ4 LS that has somewhat low hot oil pressure, under 20 PSI hot idle in drive, low enough to hear random lifter ticking (it does have over 200K). A cheap Fram Drive Ecore got it into the mid 20s, lifter tick gone so far. Or it’s getting 5W40 or 15W40, Dexos be danged!
Actually they do have a flow rate, it's a matter of at what pressure across it? Any restriction, whether it's a filter, an orifice, valve, fitting etc will have a characteristic flow rate vs pressure curve. The higher the flow rate, the higher the pressure differential across it (pressure drop). Or in other words, the higher the pressure differential you can impress across it, the higher the flow rate. Choked flow through anything is proportional to the square root of the pressure differential across it.
Flow will not occur without a pressure difference.
They might not fail but there will be a pressure drop across anything that flows and is a restriction. That pressure differential is a function of the flow rate (proportional to the square root of pdiff). And the higher the flow rate that is forced thru it, the greater the pressure differential or drop
I don't think he meant it that way. Think he was saying oil filters don't have an actual specified oil flow rate spec. I've seen some filter makers put a "flow" spec in GPM, but there is no oil viscosity or flow rate associated with that "spec", so it's purely nebulous. Yes, every flow element has a "dP vs Flow" performance curve, and the fluid viscosity is also a factor in that curve.
I've posted more about filter dP than anyone here ...
BrendanC
$100 site donor 2024
07+ LS motors will run till the cows come home at 15 psi hot idle. have multiple in the high 200k’s with 20k engine hours. of course they now get 5w-40 but they got old in age on quick lube 5w-30. LS engines are not picky and as long as the pickup o ring isn’t compromised (won’t matter what filter you have on it) they will run forever.
I’ve seen oil pressure gauge behavior differ between two brands of oil filters myself. Same oil, 5 minutes apart. My small sample size has Brand Ranks, 180 degrees out. But I digress.
Something is up with the oil pump, pressure sensor or oiling system if a filter change makes a difference in oil pressure at idle when the oil flow is low and the dP between the two different filters is only a PSI or two. Only thing that would make sense with respect to the filter is if one was defective for some reason and the defect was causing way more dP difference, which is pretty unlikely.
Exactly; that's why I got the EP
They don't have an inherent flow rate-- they take the flow of whatever circuit they are in.
The flow rate of a filter is an independent variable, that's the key takeaway here. It does NOT depend on a characteristic of the filter.
Just because you need some reference flow rate (along with viscosity) to fully specify the restriction of a filter doesn't mean that a filter "has" a flow rate. No, the restriction value has a flow rate-- because it defines a single point on the curve.
But the filter is not that point, it's the entire curve. Thus, filters do not have *a* flow rate-- they can have ALL the flow rates if you want them to. That is why it's incorrect to say a filter has a flow rate. It's not a flow rate, it's a characteristic curve along which any number of rates are possible.
On a filter, the flow rate is an independent variable. THe pressure drop (restriction) at that flow rate is the dependent variable. This is the important distinction to keep in mind as well as the source of the common misunderstanding.
So while your understanding of the mathematical relationship is correct, in the case of the effective orifice of the filter, it is the flow causing the pressure differential and not the other way around.
The PUMP is the source of flow, and all the oil pump's flow passes through the filter regardless of the filter's restriction.
^^^ To add to the above, here's some real dP vs flow data from Purolator that was done in their lab. This filter does not have a bypass valve so they were able to flow all the way to 18 GPM without the curve being impacted by the bypass valve opening. The dP vs flow curve shown will shift up or down depending on the oil viscosity.
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My 6.0l has had Mobil 1 0W-40 since I've owned it for 2 years now. 40-45psi when hot and running. It gets ChampXL filters.
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All of mine for Honda J35 series and also 1.5l turbo (same filter for both engines) are Made in Vietnam.
I only mention it bc I will likely buy it to replace my rusty, aging F-450 as my personal work truck, it’s going to get D1 & T6 5W40 after I buy it. I’m sure a Melling HV oil pump, new pickup & o-ring, and timing chain set won’t hurt it any either. I just don’t like the sound of valve ticking with hot low idle-makes me nervous!
BrendanC
$100 site donor 2024
melling 10296, pickup o-ring, timing chain, new plugs/wires and some 5w-40 and it will be a new truck. but rest assured the low hot idle is fine.
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