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can I use an H6 oil filter in the H4 ?


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18 replies to this topic

#1 boxerhummfetish

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Posted 29 November 2003 - 02:30 AM

I read from some EndWrench article that a larger oil filter is available and might fit. The larger filter area would reduce the oil pressure drop at the filter and presumably reduce the load for the oil pump. I also imagine it is less likely get fully clogged and could be used longer than the smaller filter.

Might I be able to use this in my 1.8L '95 impreza engine? Has anybody tried using the larger filter instead of the regular sized one?

Here is the endwrench quote:
"Subaru H-4 engines come from the factory with an OEM P/N 15208AA060 oil filter. The same part number is used for replacement. H-6 engines come with an OEM P/N 15208AA031, and S0A5165109 is used as a replacement. Both filters have the same physical dimensions as far as threads, O-ring, and bypass valve opening pressure (23 p.s.i.) are concerned. However, the H-4 filter has 141 square inches of filtration surface, while the H-6 filter has 201 square inches of filtration surface. The H-4 filter should not be used on the H-6 engine. Using the H-4 filter may cause it to become contaminated faster and allow the bypass valve to open, allowing unfiltered oil to circu-late through the engine."

#2 1 Lucky Texan

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Posted 29 November 2003 - 02:52 AM

I'm sure others will reply with more specific info. I have read that the H4 filter is 'dished' in such a way that some filters do not engage enough threads.

The H6's filter 'seems' to be a little more standard. If you get the Purolator part numbers for them and do a 'reverse lookup' at the Purolator site, many cars use the H6's filter (a LOT of Honda's - so any larger filters known to fit them may fit the H6, increasing its capacity too!) but the H4's part# seems limited mostly to soobs. It's been awhile since I looked all this up. Hope I got it right. Still, it may just be a matter of finding/making a longer 'stud' to replace the one in the H4. And of course it must clear any obstructions near the mount area.

#3 alias20035

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Posted 29 November 2003 - 03:18 AM

Originally posted by boxerhummfetish
I read from some EndWrench article that a larger oil filter is available and might fit. The larger filter area would reduce the oil pressure drop at the filter and presumably reduce the load for the oil pump. I also imagine it is less likely get fully clogged and could be used longer than the smaller filter.

Might I be able to use this in my 1.8L '95 impreza engine? Has anybody tried using the larger filter instead of the regular sized one?

Here is the endwrench quote:
"Subaru H-4 engines come from the factory with an OEM P/N 15208AA060 oil filter. The same part number is used for replacement. H-6 engines come with an OEM P/N 15208AA031, and S0A5165109 is used as a replacement. Both filters have the same physical dimensions as far as threads, O-ring, and bypass valve opening pressure (23 p.s.i.) are concerned. However, the H-4 filter has 141 square inches of filtration surface, while the H-6 filter has 201 square inches of filtration surface. The H-4 filter should not be used on the H-6 engine. Using the H-4 filter may cause it to become contaminated faster and allow the bypass valve to open, allowing unfiltered oil to circu-late through the engine."



You've got it all covered....

So long as the filter is only "taller", it will work. I am not sure whether there would be any significant improvement. The H6-30 flows a lot more oil than your EJ18 and needs that bigger filter.

The use of an oil pressure gauge would really help determine any benefit. The oil pump in the EJ series engines is very good (aside from backing plates occasionally coming loose). It is not at all like the notoriously bad oil pump in the EA81/2 engines.

I run Mobil 1 Synthetic, and often run 8,000 or even 10,000 km between oil changes, Subaru recommends 12,000km except in extreme use (extreme use pretty much applies to everyone though). 90% + of my driving is on the highway which really does not "dirty" the oil to the extent that city driving does. I had one used oil analysis performed after 8,000 km and the oil was rated in extremely good (almost new) condition, good for at least another 8,000km, but I had already dumped the oil already (I dumped and tested the oil to determine if I had coolant leaking into the oil (I didn't)). I have also cut used oil filters apart and they are always very clean.

Today's engines are VERY clean and today's oils are VERY good, but the filters????

Rather than using a "bigger" filter, why not use a "better" one. Finding out which one is "better" is not easy though. From experience I know that Fram and Purolator filters cause clicking lifters on hydraulic lifter equipped EJ series engine. I used Bosch on my 1993 Legacy EJ22 almost exclusively without any problem. On my 2001 Outback I have used Bosch, K&N and I now have a Wix on it. I don't notice any difference in start up and running oil pressure with any one of them though ( I added an aftermarket oil pressure gauge with low/high pressure alarm to my 01 OBW).

There are some web sites devoted to dissabembling oil filters and rating them. Try http://www.bobistheoilguy.com/

Most European cars will now run Synthetic oil for 30,000km or more, with only intermediate oil filter changes and engine oil analysis every 6,000 km to determine when the oil is going to go bad. This practice should be crossing the Atlantic to our shores sometime soon when used oil analysis labs become more commonplace.

You actually have to test the oil in a lab to determine if it has gone bad, it is not something you can determine by mileage anymore.

#4 benebob

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Posted 29 November 2003 - 09:53 AM

Not sure on the 3rd Gen H6 but the first and second use virtually the same filter as the 4 cylinder. Not sure the dif for the XT6 2.7 but the SVX's is the same size and shape. The difference is there is a valve which keeps the oil from draining back so it is always full. If you go to an autoparts store though it'll list the same oil filter as the Legacy or EA82 for both the XT6 and SVX

#5 boxerhummfetish

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Posted 05 February 2004 - 01:02 AM

Yup, Lucky Texan is a tome of knowledge: "H4 filter is 'dished' in such a way that some filters do not engage enough threads."

I tried this and bought both filters, compared them. The threads on the H6 filter are recessed more, in fact you would be missing about 2-3 turns. (I so didn't bother mounting it.)

So there is no way to use the H6 filter in the H4's.

(BTW, the cannister for the supposedly higher area filter is roughly the same size as the H4. There must be simply more folds in the H6 filter.)

#6 cookie

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Posted 05 February 2004 - 01:37 AM

you can match up. We used to have to add filters to engines like VWs and Motorcycles. I had a Pontiac filter base I cut down for my Norton and ran the oil through the frame for more capacity and cooling.
When we used to hot rod engines we often had to move the filter to get it in the car.
This led me to opening boxes at auto parts stores and comparing a lot.
Just make sure you have the same thread, depth, and make darn sure the sealing ring is in the correct location and the correct width.
When I put a Ford 289 in a Datsun Z I used a two filter remote Ford gang with the long Ford truck filters. Gave me a fair bit more oil in the system coupled with a Bronco pan and dropped the oil temp about 20%.
Use a good quality filter and if it has an anti drainback valve stock I like to use one with the same features.

#7 boxerhummfetish

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Posted 05 February 2004 - 01:45 AM

well, it might fit with two to three whole turns missing, but i think it would be foolish run with such a questionable setup. Not worth it for the few extra folds of the h6 filter anyway.

#8 Commuter

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Posted 05 February 2004 - 12:28 PM

So there is no way to use the H6 filter in the H4's.



Not quite true. I found out about the "short" filter stud on the H4's a few years ago. I wanted to use a certain alternate oil filter, and it would only catch about 1/2 turn. Meanwhile, I was told that several other people with Subaru H4 engines were using this particular filter without issue. (I also read of this issue on i-club.)

After some studying and pulling out the stud (it is symmetrical, end to end), I decided to use a washer to make it extend a little bit further. An Aluminum drain plug washer (or fill plug maybe) for a Honda transmission turned out to be just the right size with a good thickness to it. I put the washer in and now I get a full three turns of thread catching.

Disclaimer: Just a word of caution. This is what I did for my 97 OB 2.5L engine. If anyone wants to try the same, you do so at your own risk. If you ever put a Subaru specific filter back on, there is the possibility of interference and an improperly tightened seal.

The 'short' stud is why Purolator has a specific oil filter part number for the H4 engines (14460). The more generic oil filter (14459) fits a whole slew of vehicles. The primary difference is the "dishing" of the endplate. Many oil filter brands are not dished (concave) so much, and hence they will catch the threads sufficiently.

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#9 blitz

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Posted 05 February 2004 - 05:45 PM

Originally posted by Commuter
The 'short' stud is why Purolator has a specific oil filter part number for the H4 engines (14460). The more generic oil filter (14459) fits a whole slew of vehicles. The primary difference is the "dishing" of the endplate. Many oil filter brands are not dished (concave) so much, and hence they will catch the threads sufficiently.

Commuter



I'm not 100% on this but I thought there was also another difference between them regarding the 14459 having an anti-drainback valve, and the 14460 not having one, or something like that? If someone knows different, feel free to correct me.:confused:

#10 99obw

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Posted 05 February 2004 - 06:09 PM

AFAIK the H6's filter mounts horizontally, so it would need a ADBV. The H4's filter mounts vertically, so it doesn't necessarily need one.

#11 cookie

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Posted 05 February 2004 - 06:12 PM

I am still sure there is a larger filter that would fit with no mods.
These days I hate to do a mod to a system I might have someone else service someday.
It is hard enough to get folks to put the oil in the right hole in a Subie.

#12 99obw

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Posted 05 February 2004 - 06:26 PM

FWIW, I use an Amsoil SDF-20 filter. It is a really good filter. I looked on BITOG and supposedly the SDF-36 is 1/3 longer. Too bad I have about 6 SDF-20's in the shop.

IIRC another filter that I have used on the Phase I 2.5 is the 3593a. Here they talk about oversized alternatives for that filter.

#13 cookie

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Posted 05 February 2004 - 06:30 PM

This was something I planned to look into and you have done all the research for me.
Tonight I am going to start fitting KYB struts and new brakes.
Anyone in the Bay area need some used Forester bits?
Brake drums don't look too bad at all and the rotors might be turnable.

#14 blitz

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Posted 06 February 2004 - 09:52 AM

Originally posted by 99obw
AFAIK the H6's filter mounts horizontally, so it would need a ADBV. The H4's filter mounts vertically, so it doesn't necessarily need one.



I've seen this topic bantered around a bit, and there's a convincing argument suggesting that the ADBV is as much about keeping oil up in the block galleries as it is about keeping it in the filter. Apparently the oil in the galleries is capable of siphoning back to the pan via the same path it was pumped up through, actually working it's way back through the pump clearances (albeit slowly). The presence of an ADBV acts like your thumb over the end of the hose when you're siphoning gas.

The dealer part (the Subaru-branded/Purolator-made filter) for the four-banger DOES have an ADBV, so I'm not sure if the engineering dept. saw clear benefit for including it for a vertical-mount filter, or it's inclusion is a carry-over from a previous design mounting-configuration. :confused:

FWIW, I've been using the parts-store 14460 without the valve, and haven't had any catastrophe, yet I'm concerned by the possibility of some small x-tra percentage of wear at startup.:(

#15 99obw

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Posted 06 February 2004 - 05:25 PM

I see your point, but the H4 has to be about the best engine configuration regarding the draining of the oil from the galleries, with most engines being worse in this regard. A V engine or inline engine has a much greater verticle drop from the top of the engine to the oil pan. With that in mind I would think that all oil filters would have ADBV's, but they don't. It would be interesting to know how the volume of oil in the galleries compares with the volume of oil in the filter. I was just trying to explain the possible lack of an ADBV on the H4 filter.

I have always used filters with ADBV's. Not intentionally, but it has turned out that way.

#16 cookie

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Posted 06 February 2004 - 05:41 PM

with the fact that these cars have to be the oddest vehicle I have ever checked oil on.
I know most of you folks are used to them and have developed your own methods.
I am now trying to run the car the same distance, park in exactly the same place, and allow exactly the same time to drain back to get consistant results on oil level.

#17 blitz

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Posted 06 February 2004 - 08:28 PM

Originally posted by 99obw
I see your point, but the H4 has to be about the best engine configuration regarding the draining of the oil from the galleries, with most engines being worse in this regard.

I hear ya. I don't even understand how they get the oil to drain back from the heads during operation.

A V engine or inline engine has a much greater verticle drop from the top of the engine to the oil pan. With that in mind I would think that all oil filters would have ADBV's, but they don't. It would be interesting to know how the volume of oil in the galleries compares with the volume of oil in the filter. I was just trying to explain the possible lack of an ADBV on the H4 filter.


But the Subaru/Purolator part DOES have an ADBV. It's the aftermarket Purolator that doesn't. This bugs me everytime I save a couple bucks by using one.

#18 blitz

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Posted 06 February 2004 - 08:37 PM

Originally posted by cookie
with the fact that these cars have to be the oddest vehicle I have ever checked oil on.
I know most of you folks are used to them and have developed your own methods.
I am now trying to run the car the same distance, park in exactly the same place, and allow exactly the same time to drain back to get consistant results on oil level.


It's a bugger to get a reading at all, let alone an accurate one.:banghead:
I check it with the car parked in the same spot I where I've refilled it after an oil change, so at least I have a baseline as to any consumption. After I shut it off and pull the stick, I have to wait about a half hour before I can actually go back and check the level without getting a big oil smear on the dipstick.

#19 99obw

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Posted 07 February 2004 - 10:54 AM

I have been checking the oil at the gas station. The concrete pad at the Mobil nearby is pretty level. I shut off the car, fill the gas tank, fill the washer fluid, then check the oil. Works really well. I need to take a torpedo level with me to find a place on the car that I can use for a level reference, then find a level enough place in my driveway, which is far from flat. My shop floor is significantly sloped for drainage, so that doesn't work very well either. The suby is the most sensitive car I have ever seen in this regard.

One trick is to only check the oil when it is either stone cold or fully warmed up. In between and it takes forever for the reading to stabilize.




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