Donaldson P550318 vs NAPA Gold 1521: Oil Filter Compatibility
Compare Donaldson P550318 and NAPA Gold 1521 oil filters by compatibility, dimensions, thread size, gasket fit, bypass valve, anti-drainback valve status, and match confidence. Use this comparison as a fitment review, not as an automatic substitution guarantee. Both use a 3/4-16 thread.
Quick verdict
Both use a 3/4-16 thread.
- Thread size is the first hard-fit check for any comparison of spin-on filters.
- Gasket OD and gasket ID are the most important seal-related dimensions.
- Height differences can matter for clearance even when thread and gasket fit appear close.
- Bypass and anti-drainback differences may be important, depending on the application.
Donaldson P550318 and NAPA Gold 1521 specifications
How matching is scored| Specification | Donaldson P550318 | NAPA Gold 1521 |
|---|---|---|
| Thread size | 3/4-16 | 3/4-16 |
| Gasket OD | 72 mm | 69 mm |
| Gasket ID | 62 mm | 62 mm |
| Can OD | 93 mm | 92.99 mm |
| Height | 93 mm | 96.01 mm |
| Internal bypass valve | No | Yes |
| Bypass PSID | Not applicable | 8 - 11 |
| Anti-drainback valve | No | Yes |
What matters in this specific comparison
Thread size matches: both are 3/4-16.
Gasket OD differs by 3 mm (Donaldson P550318: 72 mm, NAPA Gold 1521: 69 mm).
Gasket ID is identical at 62 mm.
NAPA Gold 1521 is 3 mm taller (Donaldson P550318: 93 mm, NAPA Gold 1521: 96.01 mm) -- check clearance before substituting.
Can OD is identical at 93 mm.
Bypass valve presence differs: NAPA Gold 1521 has one, Donaldson P550318 does not.
Open related filters
Before substituting, verify thread fit, gasket sealing dimensions, height clearance, bypass behavior, and anti-drainback requirements for your specific application.