Wix Filter/NapaGold Oil Filter vs STP
- STP uses a leaf spring rather than a coil spring; the leaf spring must always seat properly onto the end cap. Additionally, a leaf spring can bend under high pressures.
- STP uses weaker fiberboard end caps rather than the metal ones.
- The filter media inside the STP was glued to itself, rather than crimped with a metal bracket.
- STP uses a phenolic resin which helps to bind the media and protect during high temperatures.
- The STP uses a plastic-frame as its center tube; the tube is open on both ends. Only the ACDelco and the STP use this plastic frame.
- The STP filter uses a rubber anti-drain back valve. The anti-drain back valve is used to prevent oil from draining back to the crankcase after shutdown. A silicone valve is less likely to break down during high heat than the nitrile rubber.
- STP and ACDelco and had the largest flow holes of all the filters.
- STP and ACDelco weighed the least off all the filters, probably due to the weaker fiberboard end caps.