STP Gas Treatment Showdown: Odor Control vs Mach Performance...More Than You Expect! When we first unboxed the STP Gas Treatment (18027G) in our latest showdown, we were drawn to its compact 12-oz can—a small size packed with big promises. Our initial test revealed a sharp, chemical scent that tackled stubborn odors in our garage faster than expected. We were pleased, but curious about its performance on bigger issues. After introducing it into our aging engine, the results were telling: a noticeable reduction in pinging under load and smoother idling, hinting at deeper cleaning benefits. What impressed us most, however, was how the treatment balanced efficacy and convenience. Some competing products leave a film or require multiple applications, but STP delivered on both odor control and performance improvements with a single dose. A solid contender in our book.