Mario;

The dampening oil does get slowly consumed...at a rate that's obviously a function of how many miles you put on...if you're seeing the carbs in need of topping up every three months on a daily driver, that does'nt seem like an overly high rate of consumption to me either.

I check and top them in the fall when I richen the carbs three faces for the cold season, and then again in the spring when I lean them back up, and also at oil changes. I also use and recommend ATF, it has the right viscocity through the operating temperature range, is available everywhere, and is not harmfull when consumed by the engine.

Cheers