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Oil filter by-pass valve position - threaded or dome?

10K views 10 replies 6 participants last post by  Jeepman 
#1 ·
The oil filter on my 3.3l Chrysler is vertically mounted. Does it make any difference whether the oil filter's by-pass valve is located in the threaded base end or the dome end? I am wondering which would be best (if either) for cold weather starting to ensure start-up oil to the engine:confused:
 
#3 ·
I would agree, once you burp the air after inserting a new filter, It should not run back regardless. With the advance of newer oils and additives, it is very likely not a big deal anyway, since most modern oils have the tenacity to stay on the engine surfaces until the pressure gets up again during a start up, but it certainly has to be better if it gets oil even quicker.
 
#4 ·
I prefer the bypass valve at the base, like on the Mopar filters. Having said that, the unfiltered oil bypassing at the cap end probably makes no difference. In a bypass situation, it's unfiltered oil anyway. As to the filter being vertical, I wouldn't worry about that either.

How often does a bypass situation exist, that's the question. Probably more often than one thinks.
 
#5 ·
I prefer it at the threaded end. Most OEM-spec filters (like the Mopar and Motorcraft filters) specifically call for threaded-end bypass valves. The generic filter numbers use a generic dome-end bypass. As Jeepman said, bypass happens more than you probably think it does, and with a threaded-end bypass, the sediment that will naturally build up in the dome end of a vertical-mounted filter doesn't get disturbed.

Given a choice, go with the threaded-end bypass.
 
#6 ·
The Fram Tough Guard 8A has a screen over the bypass valve (located at the cap end). Here's a picture of it (on the right side in the picture).

Some people use magnets on their filters to attract any metal pieces or go for the Force Field pre-filter magnet shown here. That sounds useful.

Then again, there's the efficiency of your filter as purchased. The Fram TG8A above has a dirt trapping efficiency of 99%. Apparently some filters have efficiencies as low as 80%. If they don't tell you their % efficiency, in their technical information, may as well assume a lower efficiency.

For information purposes only, I have included a picture of the bases of a Mopar, Wix Premium and Fram TG8A filter, showing the color of the anti-drainback valve (a different animal than the bypass valve) materiel, which can be seen through the smaller hole around the center hole. The oil from the oil pump passes through these smaller holes, enters the filter chamber, goes through the filter media, then out the center hole, then up to the engine. The dirt in the oil is "trapped" (not just stopped) by the filter media. The orange anti-drainback material is silicone, a superior materiel to the black nitrile in the Mopar.
 

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#8 · (Edited)
The Mopar filters (Wix in Canada, Purolator in the US) have the bypass valve at the base (where the holes are and just in back of the anti-drainback valve). The Wix premium has the bypass valve at the base. Take a look here.
I attached a picture of a Wix premium filter that I cut apart.
I believe the various Manufacturers have filters with the bypass valve at either end, depending on which level of filter you buy, or what the vehicle manufacturer specifies (such as Mopar).

Note: Anyone interested in the Fram Extended Guard, take a look here, it's impressive. It's no low end filter for sure. Holds 30 grams of dirt at 97% efficiency versus the Pure 1 at 12 grams and 99.9%.
 

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#9 ·
Ice in winter?

I have heard about the oil picking up crud if the bypass valve is in the dome position and opened, but I came across this one in browsing the internet. In very cold winters, like we have in Minnesota, moisture can collect at the bottom of the oil filter and freeze. This ice will then inhibit the operation of the dome valve on cold startup. Any opinions on this? It could be another reason to use a threaded bypass filter.
 
#10 ·
Your oil has emulsifiers in it to prevent oil from separating. If you have that much water int he oil, you have bigger problems as any drive over 10 miles will heat the oil enough to boil out any water. That should be a non issue.
 
#11 ·
If there were a problem with the bypass valve being in the cap end of the filter, there would be a warning in the Owner Manual not to use that type of filter, I would think. There is mention in the Owner Manual about other oil related criteria such as no additives, no flushes, using API Certified oil and meeting the requirements of Chrysler Material Standard MS-6395. They don't even allow 0W-XX oils, has to be 10W-30 or 5W-20 for the 5th Generation.

Here's what it says about the oil filter:
The manufacturer’s engines have a full-flow type oil filter. Use a filter of this type for replacement. The quality of replacement filters varies considerably. Only high quality filters should be used to assure most efficient service. MOPAR engine oil filters are a high quality oil filter and are recommended.
I don't know about the high quality of Mopar oil filters. They have the lower quality anti-drainback valve (nitrile versus silicone) and it's anybody's guess as to their dirt trapping efficiency. You would think Chrysler would set some minimum standards ..... well, I guess they do ..... their Mopar filter, which in Canadian vehicles is made by Wix in the US and has a nitrile anti-drainback valve. Go figure on that one. In the US, the Mopar oil filters are made by Purolator and have a nitrile anti-drainback valve..

Royal Purple says:
Prevents dry starts by eliminating oil drain back during shutdown through the use of a silicone anti-drain back valve. Silicone outperforms and outlasts standard nitrile rubber in both extreme cold and hot oil temperatures.
Wix says:
Silicone Anti-Drainback Valve - Stays flexible in extreme temperatures, improves oil flow and keeps oil in filter to prevent engine destroying dry starts. Also provides lasting protection to meet new vehicle manufacturers longer recommended oil change schedules. Nitrile valves can harden and become ineffective over time.
Although one may have a preference for the location of the anti-drainback, its location doesn't really seem to matter.
 
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