Just curious but what kind of filter. And yes viscosity can affect it but also remember the drill rpm doesn’t duplicate engine rpm. Years ago I ran 40 weight, then 30, then 10-40, now 10-30. With the RacePak I can closely watch what is going on during a pass and in the pits.

1970 Duster
Edelbrock headed 408
5.984@112.52
422 Indy headed small block
5.982@112.56 mph
9.42@138.27

Livin and lovin life one day at a time