1999 Silverado pre ignition
 

I had a bad pinging pre ignition problem. I added a gas treatment and higher octaine fuel and drove it off and on because I have another vehicle and im afraid of blowing a head gasket. Ive done this for two months with it coming and going. Two weeks ago the outside temperature dropped down to the lower thirties and the level in the overflow bottle was down. Was this because of the tempature? Now the pinging is gone and truck runs strong. Could I have a small head gasket leak? Im getting a intake treatment this week to break up carbon deposits. Any ideas?