Tweet
This is a testimonial to Don's support of MMO. I compression test my engine every spring after launch, and have had a gradual drop in compression, 90-100 5 years ago to the 70s this year, even after adjusting valve lash last fall, which increased pressures by a few pounds and brought the pressures closer together from cylinder to cylinder. I did the MMO treatment (preceded by spraying carb cleaner toward the valves) last week, let it sit a few days before burning it off, and now have over 110 in all cylinders. Now I'll take it on a good long high speed cruise to finish the job.