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2012 OB , 2017 Impreza
4,747 Posts
There is a long sorted history regarding Subaru engine oil-filters.

Back when the filters were installed underneath the engine... the physically larger filters would place the filter-can within 1/2 inch of exhaust plumbing. This resulted in the oil getting heated by the exhaust system. Hence, Subaru changed to physically smaller filters which solved that problem (but now there was less filter-media and the filters needed to be changed 1/2 way thru each oil change.)

There are some folks who point to the filter-specification regarding overpressure valve opening. From this perspective, Subaru oil-filters are very unique in the auto-industry. There are not many filters on the market which meet the same overpressure specification as the Subaru filters.

The overpressure valve ONLY comes into play when oil is cold (thick) and cannot pass thru the filter-media fast enough... the valve opens to allow oil to get to the engine (BUT THE OIL IS NOT FILTERED) This condition may NEVER occur for most cars unless you live in VERY cold climate and over-rev cold engine.

Of-course, when the oil filter is mounted upside-down ON TOP of the engine, then the anit-drainback valve within the filter becomes an important consideration. Lest the oil may drain out of the filter when engine is parked. This causes 'dry' startups which can, over time, destroy bearings. (The engine is starved for oil for several seconds EVERY time the engine is started)

To more-specifically answer your question... as a general rule, a physically larger filter allows for more filter media within the can. This is a GOOD thing.

In the end there are MANY considerations regarding oil-filters besides "does it fit"
  • Overpressure valve
  • Anti-drainback valve
  • filter meda micron-size
For some folks, they feel that filters are cheep considering the cost of the engine. Those folks ONLY use Subaru-branded filters.

For other folks, they feel it is more important to CHANGE the oil/filter often than to spend extra on more expensive items.

Your car - your choice 😁
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