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Swapping Oil Filter sizes

Early on I discovered that the oil filters used on the 4-cylinder and 6-cylinder Subaru engines are identical insofar as the bore, threading, seal, etc. The one for the 6-cylinder is just a little longer and larger in diameter for more oil capacity.

I can understand why you wouldn’t want to use the small filter on the larger engine, but would there be anything wrong in using the larger filter on the smaller engine? I’d think it’d give you a little more oil capacity which would result in the oil staying a little cooler, not to mention more filter surface.

I Wouldn't Experiment.

I had two cars, same make and model (not Subaru) The V-6 took a shorter filter of the same diameter as the longer filter on the smaller displacement 4-cylinder. I'm not going to second guess the engineers.

Also, sometimes filters don't have a lot of clearance, maybe your's does, but don't forget that engines move when they're running and the car's going down the road. Space is sometimes part of the design.

Want cleaner oil ? Change it more frequently.


Yeah, I wouldn’t, not much to be gained. The only time I did this was when GM went to smaller filters on the same engine. But different engines? I’d pass.

Why change the oil capacity? If four ounces made that much difference, people on TV would be shouting at you to buy their brand of enlarged oil filter. TV is always telling us the truth, right? The sales people at the car dealer would want you to buy the optional eight quart oil pan.

The old Chevy SB V-8 has 3 or 4 different size filters that will fit, the longest one holds almost 2 quarts of oil ! The Ford and Chrysler filters also come in different sizes and capacities… Which filter you use is up to you…

There must be over a hundred different screw-on oil filter numbers…Many of them share the same base-plate… It’s called “Shelf Space” I bet 10 would completely cover the market…

Actually I’ve been running the larger one for 4 years now with no apparent problems. I did the same thing on an older Jeep with AMC straight 6-cylinder, that would also mount the longer V-8 filter (identical base plates as well).

I only began wondering as recently I’d been having trouble finding the 6-cylinder filter at my local auto parts house and if there was any benefit, I was going to mail order a few to get me by. I just started wondering if it really made any difference.

But the other factor to watch is often an un-known,....the by-pass valve pressure.

The filter may FIT but at what point do you risk cycling un-filtered oil ?

About 15 years ago I made this very mistake – using the oil filter for my Buick on my Arrow pickup truck. Or was it the truck’s filter on the Buick? Anyway, I discovered the mistake at the next oil change. There was no apparent problem caused by the accidental swap. So I tend to agree with Caddyman’s hypothesis that many oil filters could be considered interchangeable.

I’m sure many filters can be used in lieu of many others. But I’m not willing to risk an engine worth thousands of my hard-earned dollars to test my particular application. The question is, are YOU willing to?

My 4Runner has the V6. There was a V8 option. The difference between the V8 filter and the V6 filter is about 1.5 inches. I asked at the dealership what the difference was, and if they both fit. The answer (from the mechanics, not the sales guys), was that the larger did indeed fit the V6, and it provided more filter area so the engine could actually push more oil through with less resistance.

I’ve been using the V8 filters ever since. Over 100K now, and there’s no negative here for me.

I’ve had this car for almost 5 years now and as I recall, the first time I changed the filter I noticed that the replacement was much smaller than what had come on it. So Subaru had actually installed the larger filter on the car from the factory. That was what convinced me it would be okay to keep on running the larger one. I never gave it a second thought until recently, and apparently there is no real cause for concern. Thanks.

  • Whithholding And Rationing Information
  • Not Giving Credence To Suggested Advice
  • Reaching A Pre-Determined Conclusion

Guilty as charged. I guess just keep doing what you've been doing and what you were going to do, anyhow.

This whole discussion was like Kissing One's Sister !



CSA - as I once wrote to Car and Driver - red and yellow are like ketchup and mustard on your food, to be used sparingly, not sprayed around like Reddi Whip on your pumpkin pie at Thanksgiving!

p.s. - green, too!

Years ago, I had a hydrostatic drive 14 horsepower riding lawn tractor made by MTD, but sold under the name of Farm King by Quality Farm and Fleet. The hydrostatic fluid was filtered with a regular oil filter and the manual called for a particular type of Fram oil filter. I had changed the hydrostatic fluid (it was Type F transmission fluid) and picked up a house brand filter that a cross reference book showed was equivalent to the Fram filter. I was mowing along and suddenly the tractor quit moving. It turned out that the house brand filter was about 1/2" longer than the Fram filter and every time I raised the mower deck, a support brace would hit the filter. Eventually, it poked a hole in the filter and I lost all the fluid.

I don't think this would happen with a car, but I have always been a little gun shy about substituting a different filter.

Before I get anyone too upset, remember this is just my experience, and just with one vehicle (I cannot do it with my others). I went to the dealer trained mechanincs, and asked the appropriate questions.

I'm NOT saying this is acceptable for every vehicle, or even for yours. You need to talk to the master mechanics on site if you decide you want to use something other than what's called for, and what any possible negative impacts may be.

Of course, IF you've already done that, and determined that the larger filter IS acceptable for your vehicle, will work with no negative side effects, and have already done it, then even asking us was silly.


TXes, Sorry About That !

I Guess It's Kind Of Like Eating Sauer Kraut And Strawberry Jello Together, Eh !


Well put, texases. If you don't mind, I might use that (with attribution, of course!) when we rewrite/beef up the discussion rules.

Wow, CSA, kissing one's sister, and eating sauerkraut and strawberry jello? Your imagery is very...powerful today.

Back in the 70's Ford had ONE filter for all their engines....The Fram designation was PH-8a. Didn't matter if it was a 302, 351 or the Pinto 2.3l....they all used the same filter.

When I owned my GMC S-15...GM changed the filter design on that engine (2.8L) at least 3 times for the 6 years I owned it. I guess they were having a problem with oil.

Personally I wouldn't change filters...I'd stick with any decent filter manufacturer's recommended filter for this engine....Why take a chance??

I wonder if one could have an anti-drain back valve to help provide oil pressure sooner after starting the engine. Is one of them mounted with top down and the other with the top up?

I asked because I had started wondering if it was an acceptable practice. What is sold for this engine by all the popular filter makers is a teeny, tiny filter - much smaller than what originally came on it.

I would just buy a filter from Subaru and use what they suggest but there is no dealer within about 50 miles of me.