Discussion of oil filters is endless. I'll start by saying Yanmar seems to use the common Subaru/Honda filter mounting. But then there have been improvements in specs since the 1980's when our Yanmars were built.
Fredricks etc catalog lists '1334' for their oil filter so I'm guessing it is equivalent to a Wix 1334 / NAPA 51334.
Here's a comment I found re 1334 and later improved equivalents. I think this represents current thinking on the subject. It's in a reply on
this site:
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"We found that the best filter to use on Subarus is the one specified for the 2009+ Mazda RX-8. It is 100% compatible with the Subaru thread pitch and has both a better filtration media spec and larger oil capacity by several ounces.
The older style large Subaru filters are still available from Blank as well, but the filter media spec is actually inferior to the new Subaru filter. The filter media area is larger so it has more capacity for dirt and will last longer, but the new smaller filter does a better job of filtering when new.
51334
3.194″ height
3.252″ diameter
0.45 quarts based on exterior dimensions, but probably only holds closer to 0.40 quarts
Beta 2 test: 50% of >=22 micron particles captured 1st pass
Beta 20 test: 95% of >=40 micron particles captured 1st pass
Standard OEM size for older 4-cylinder and all 6-cylinders; won't fit most newer 4-cylinders due to updated exhaust system
Has more oil capacity than 51365
OK filtration.
51365
2.577″ height
2.685 diameter
0.25 quarts based on exterior dimensions but probably only holds closer to 0.20 quarts
Beta 2 test: 50% of >=15 micron particles captured 1st pass
Beta 20 test: 95% of >=22 micron particles captured 1st pass
Standard size for newer 4-cylinders.
Good filtration.
51356/57356
3.402″ height
2.685″ diameter
0.33 quarts based on dimensions, but probably holds closer to 0.25 quarts
Beta 2 test: 50% of >=6 micron particles captured 1st pass
Beta 20 test: 95% of >=19 micron particles captured 1st pass
Not a standard size for Subaru, but should fit all 4-cylinders and 6 cylinders. Installation may be a little more difficult on 6-cylinder due to the length.
Best filtration.
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Note the later Subarus have an issue with the Catalytic Converter moved up closer to the exhaust manifold where it cooks the oil filter, apparently the reason for Subaru now standardizing on a smaller filter across all models including old models. We don't have that same need for a smaller filter. Seems to me larger is better (unless there is a mounting bracket in the way).
Personally I'll keep using the NAPA Gold 51334 but those improved filters might be worthwhile for someone running more hours/year. And on a cold start I'll always crank with compression released until the oil light goes out. That should overcome any issue with a drainback valve.