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#4754900 - 05/12/18 09:38 AM STP Air Filter Efficiency
JerryBob Offline

Registered: 04/11/13
Posts: 939
Loc: Colorado
I watched my cousin changing the air filter in his Jeep using an STP filter.

The box said 90% efficiency. That struck me as very low. Shouldn’t it be in the high 90s?
Certified Filter Cutter - License #F-23567 Expires 12/2019

#4754906 - 05/12/18 09:46 AM Re: STP Air Filter Efficiency [Re: JerryBob]
mrsilv04 Offline

Registered: 12/08/06
Posts: 8197
Loc: Illinois
90% efficient at what? Filtering out gravel sized chunks? Unfortunately, there's not a lot to go on here.

However, this is likely a case of where your cousin got what he paid for... or less than he paid for.

I can buy a $3 oil filter, and see the spec is 99% at 30 microns... right on the box. For what I'm trying to accomplish, that's plenty good enough.

Air filters may not be as straight-forward.
2004 Silverado - on its 3rd Jasper engine in less than one year.

#4754925 - 05/12/18 10:07 AM Re: STP Air Filter Efficiency [Re: JerryBob]
Linctex Offline

Registered: 12/31/16
Posts: 5950
Loc: Waco, TX
Originally Posted By: JerryBob

The box said 90% efficiency. That struck me as very low. Shouldn’t it be in the high 90s?

Not enough information available to make an informed decision.

Yes, really.
"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."

#4754985 - 05/12/18 11:24 AM Re: STP Air Filter Efficiency [Re: JerryBob]
Jim Allen Offline

Registered: 08/12/05
Posts: 4547
Loc: NW Ohio
The only way to know is to query the manufacturer. That is an odd spec to list given that other manufacturers list higher numbers. It wouldn't be a horrible filter if it was a test made on find dust. That would equate to somewhere around 95+% on coarse (which is the more common spec listed. Nowaways, most mfrs list 98 percent on the coarse dust test and some at 99% (one percent counts for a LOT in an air filter and 4-5 percent is HUUUUUGE). 90% isn't much better than an oil bath filter and they suck (literally and figuratively).
Jim Allen
Keepin' the Good Old Days of Four Wheeling Alive

#4755169 - 05/12/18 03:57 PM Re: STP Air Filter Efficiency [Re: JerryBob]
mazdamonky Offline

Registered: 12/08/15
Posts: 551
Loc: Arkansas
Sadly, this number sounds not good to me, though we don't know what the 90% efficiency rating is for. Sadly, this is the only filter I can get locally for my 85 rx7. Everything else has to be ordered online and Fram has pretty much stopped making that filter so you can't get it anywhere.
1985 rx7 1.1 98k miles
2002 protege 220k miles
1985 rx7 with a 5.0 swap
2002 Protege 292k miles Girlfriend's
4 more running cars in yard not mentioned

#4755501 - 05/13/18 12:57 AM Re: STP Air Filter Efficiency [Re: mazdamonky]
Malo83 Offline

Registered: 08/08/08
Posts: 1969
Loc: Cali
I run 2 STP filters on my DD 83 Silverado with no problems, oil and air get them at AutoZone. thumbsup

#4755548 - 05/13/18 04:44 AM Re: STP Air Filter Efficiency [Re: JerryBob]
bbhero Offline

Registered: 03/20/15
Posts: 4499
Loc: Virginia
Yeah I saw that the other day in AZ. And I was like holy cow that is substandard.

I thought the back of the box should have read: "This air filter only catch large insects, hummingbirds, and large pieces of gravel. This air filter is not intended for the meaningful use of small particulate filtration".

Edited by bbhero (05/13/18 04:45 AM)
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