I was told to use it about every 3rd fill-up or until teh problem clears, but no more than 4 times total between oil changes. Are you the original owner? If so and you have been using Top Tier fuel since new, your problem is not likelyto be carbon build-up on the backs of the valves.

Hi,

I live in the valley as well and I got a 2009 991 cab. I've had the same pinging problems that you seemed to have. I use Shell gas, but I have only added Techron once. How often did you add the fuel additive to get the pinging to stop.

Thanks,
Todd