Some kid came into my tire shop in a late 90s eclipse with the 2.0 (dodge?) N/A engine. Has a PH16 on it. He wants our <$20 bulk oil special which includes filter but he brings his own NAPA silver anyway. Thimble sized thing. (Wish I remember the part #.) Curious, I check out the baseplate, stamped "20" (mm), probably for a different Mitsubishi engine. I cover the box with greasy fingerprints and toss it back at the service writer. He tells me to grab a new PH16... which I know off the back of my head (via incessant BITOG threads among other sources) has 3/4" thread. 20mm strikes me as being just oversize enough to blow off eventually, later. Not sure what the kid thought he'd gain with the stunt. Any new engine on our nickel wouldn't have had his spray painted valve cover... he "customized" everything including the coils and plug wires.