NAPA Gold 1521 vs MAHLE OC 25: Oil Filter Compatibility
Compare NAPA Gold 1521 and MAHLE OC 25 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.
NAPA Gold 1521 and MAHLE OC 25 specifications
How matching is scored| Specification | NAPA Gold 1521 | MAHLE OC 25 |
|---|---|---|
| Thread size | 3/4-16 | 3/4-16 |
| Gasket OD | 69 mm | 71 mm |
| Gasket ID | 62 mm | 61.7 mm |
| Can OD | 92.99 mm | 93.98 mm |
| Height | 96.01 mm | 98.55 mm |
| Internal bypass valve | Yes | Yes |
| Bypass PSID | 8 - 11 | 32 |
| Anti-drainback valve | Yes | Yes |
What matters in this specific comparison
Thread size matches: both are 3/4-16.
Gasket OD differs by 2 mm (NAPA Gold 1521: 69 mm, MAHLE OC 25: 71 mm).
Gasket ID differs by 0.3 mm (NAPA Gold 1521: 62 mm, MAHLE OC 25: 61.7 mm).
MAHLE OC 25 is 2.5 mm taller (NAPA Gold 1521: 96.01 mm, MAHLE OC 25: 98.55 mm) -- check clearance before substituting.
Can OD differs by 1 mm (NAPA Gold 1521: 92.99 mm, MAHLE OC 25: 93.98 mm).
Both open their bypass valve in a comparable range: NAPA Gold 1521 at 8-11 psi, MAHLE OC 25 at 32-32 psi -- these ranges do not overlap.
Open related filters
Before substituting, verify thread fit, gasket sealing dimensions, height clearance, bypass behavior, and anti-drainback requirements for your specific application.