If the filter opening faces up and is installed under the car, as on most American cars, would there still be a need for an anti drainback valve on the filter?

On the RX7, the filter opening faces down, so the oil naturally would drain back to the crankcase hence the need for the anti drain back valve.

 

Good point, But most engines have the filter screw on the block horizontaly.

Ever take a fram filter off your rotary and it doesn't drain any oil down the side of your engine? Wonder why? Most of them don't work. Thats why I don't use that four letter F word. Well and many other reasons...

 

unfortunatly all the factory literature was rendered obsolete when mazda changed filter suppliers.

mike