Baldwin B173-S vs MAHLE OC 978: Oil Filter Compatibility
Compare Baldwin B173-S and MAHLE OC 978 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 M20x1.5 thread.
Quick verdict
Closest known dimensional difference: height -3.1 mm. Verify application-specific requirements before substituting.
- 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.
Baldwin B173-S and MAHLE OC 978 specifications
How matching is scored| Specification | Baldwin B173-S | MAHLE OC 978 |
|---|---|---|
| Thread size | M20x1.5 | M20x1.5 |
| Gasket OD | 71.4 mm | 70.8 mm |
| Gasket ID | 62.7 mm | 62.3 mm |
| Can OD | 93.7 mm | 75 mm |
| Height | 82.6 mm | 79.5 mm |
| Internal bypass valve | Yes | Yes |
| Bypass PSID | 20 | 14 |
| Anti-drainback valve | Yes | Yes |
What matters in this specific comparison
Thread size matches: both are M20x1.5.
Gasket OD differs by 0.6 mm (Baldwin B173-S: 71.4 mm, MAHLE OC 978: 70.8 mm).
Gasket ID differs by 0.4 mm (Baldwin B173-S: 62.7 mm, MAHLE OC 978: 62.3 mm).
Baldwin B173-S is 3.1 mm taller (Baldwin B173-S: 82.6 mm, MAHLE OC 978: 79.5 mm) -- check clearance before substituting.
Can OD differs by 18.7 mm (Baldwin B173-S: 93.7 mm, MAHLE OC 978: 75 mm).
Both open their bypass valve in a comparable range: Baldwin B173-S at 20-20 psi, MAHLE OC 978 at 14-14 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.