Vehicle: 06 silverado H.O 5.3L V8 (L33) This truck is tuned for 89 octane fuel. It definitely rolls out when you stomp it. Since it has been tuned, about four months, it would ping at and above 3500 rpm. Ive ran 89 octane, 93 octane, a mixture of both, different fuel adds, etc. Nothing would cure the pinging at high rpm. And Im quite sure there is little carbon internally to cause pre ignition. Two days ago I bought and added the recommended dose of 1oz per 16gal of Pri-G in 89 octane. Today I hammered on it and there was no pinging, so I got on it again. Still no pinging which is nice. I have to think 'Pri-G is highly effective at reducing pinging' as the bottle states.