Purchased a 2009 Silverado Crew Cab back in May of this year. I've noticed a "pinging" sound sometimes when I start my truck but mostly when I'm cruising at 1500rpm. I've talked a buddy about this and he said he was told it was common and it could be the type of fuel I've been using. I use Chevron Unleaded but I was told to use a higher grade to see if this helps. Any help would be appreciated.