Two of my tires have slow air leak losing pressure in 2-3 days triggering TPMS warning, and I have to pump 1 tire (other is used as spare).

Dealer and tire shop could not find the leaks. I have only 20K on tires, so would like to avoid the expense of new tires.

I looked at permaseal tire sealant (permasealtire.com). That company's rep said that their product is safe to use, and website shows wonders of their product.

However I am worried that TMPS sensors (if any, not sure about 2008 A6) might get covered and stop working, or if the sealant will change TMPS calibration in other way.

Any advice or related experience? Thanks in advance.