Boundary

The best Boundary parts for a Subaru build are its billet oil pump gears and complete oil pump assemblies, matched to your exact engine and gear size. WRX owners with the FA20 turbo engine will find 14mm billet gears, BRZ, FR-S, and 86 owners with the FA20D will find 12mm gears, and EJ engine owners will find complete S2 and high-flow Shark Tooth assemblies. Check your year, model, and engine before ordering, because FA20F, FA20D, and EJ parts do not interchange.

Oil pump gears sit at the center of the engine oiling system, and a gear failure can starve the rest of the engine. Boundary offers billet gears on their own for owners rebuilding a pump, and as complete treated assemblies for EJ engines, in standard and MartenWear treated versions, plus 12mm EJ Shark Tooth assemblies described as high flow. These parts belong in an engine build alongside the internals in our Connecting Rods collection and the wider Oil System range.

Boundary is the single brand behind every product sampled here, and oiling is its specialty rather than one line among many. For the 2015-2021 WRX, it includes the 2.0L FA20 turbo direct injection billet oil pump gear and a 14mm FA20F MartenWear version. For 2012-2021 BRZ, FR-S, and 86, it offers 12mm FA20D gears in standard and MartenWear forms. That engine-by-engine coverage, with size stated in every title, defines the brand here.

EJ owners get the most complete options here. The Subaru EJ 12mm billet gear high-flow Shark Tooth oil pump assembly and its MartenWear treated counterpart arrive as assemblies rather than loose gears, and an EJ S2 MartenWear treated assembly is also listed. Builders comparing supporting brands will find valvetrain depth in GSC Power Division and ACL bearing options, both common partners for a pump upgrade during a rebuild. For background reading, see A Guide to Subaru Engine Modifications.

Choose by engine first, then by format. Loose gears suit a planned rebuild, while EJ assemblies suit owners who want gear and pump handled together. The 12mm FA20D billet gear for 2012-2021 BRZ shows why the title matters: it names engine, size, and year range in one line.

What is the difference between the FA20F and FA20D gears?

They fit different engines and cars. FA20F gears here are for the 2015-2021 WRX 2.0L turbo, while FA20D gears are for the 2012-2021 BRZ, FR-S, and 86. They do not interchange, so check your year, model, and engine first.

Should I buy a loose gear or a complete assembly?

Loose billet gears suit a pump you plan to rebuild, while the EJ S2 and Shark Tooth options sampled here are complete assemblies. If you are unsure which route your build needs, ask your engine builder before ordering.

What does the MartenWear option mean here?

Several gears and assemblies in this collection are listed in both standard billet and MartenWear treated versions, including WRX, BRZ, and EJ parts. Compare the two listings for your exact engine rather than assuming one version fits every car.

Is an oil pump gear a beginner install?

No. Oil pump work is internal engine work that normally happens during a rebuild or major service, not a simple bolt-on. Most owners have a qualified engine builder fit these parts and verify oil pressure afterwards.