California Smog Check for 924s

[Rich323ard]

I thought I'd share a revelation. My 924s has always struggled with passing the California smog check every 2 years. I have always had to be diligent leading up to the test. Using a bottle of "Garranteed to Pass" amd switching to cold spark plugs. It works, but the passing numbers are always marginal.

This last test, after I changed the oil, I added a can of STP ceramic additive, drove the 924s around a mountain road to warm it up and get the cat hot.

To my surprise, the 924s passed the smog test with flying colors. A wild difference, the numbers were halved. The ceramic must be sealing up the piston rings and seals better?

[spacecad3t]

Who knows. I use a 10w-40 with "MoS2" additive and every engine from 1938-2015 that Ive added it to, it has quieted up and in some cases "leaked less".

[dr bob]

I'm curious to know which part of the test your car struggled with. Each part has particular causes, like high HC is typically related to misfires. Of course, a misfire is a symptom of any of several possible "problems". Ditto the CO and NOx elements.

Share if you can please.

Thanks!