Baldwin BT259 vs Donaldson P550518: Oil Filter Compatibility
Compare Baldwin BT259 and Donaldson P550518 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 13/16-16 thread.
Quick verdict
Large bypass PSI mismatch: 6.5 psi · Candidate adds ADBV
- 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 BT259 and Donaldson P550518 specifications
How matching is scored| Specification | Baldwin BT259 | Donaldson P550518 |
|---|---|---|
| Thread size | 13/16-16 | 13/16-16 |
| Gasket OD | 91 mm | 88 mm |
| Gasket ID | 80 mm | 79 mm |
| Can OD | 93.7 mm | 94 mm |
| Height | 137.3 mm | 136 mm |
| Internal bypass valve | Yes | Yes |
| Bypass PSID | 20 | 12 - 15 |
| Anti-drainback valve | No | Yes |
What matters in this specific comparison
Thread size matches: both are 13/16-16.
Gasket OD differs by 3 mm (Baldwin BT259: 91 mm, Donaldson P550518: 88 mm).
Gasket ID differs by 1 mm (Baldwin BT259: 80 mm, Donaldson P550518: 79 mm).
Baldwin BT259 is 1.3 mm taller (Baldwin BT259: 137.3 mm, Donaldson P550518: 136 mm) -- check clearance before substituting.
Can OD differs by 0.3 mm (Baldwin BT259: 93.7 mm, Donaldson P550518: 94 mm).
Both open their bypass valve in a comparable range: Baldwin BT259 at 20-20 psi, Donaldson P550518 at 12-15 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.