What is this pinging that people talk about? A guy in another thread had a truck similar to mine and said he took it to the ford dealer and had them slow the timing blah blah to reduce the pinging and it helped increase his gas mileage from 16 to 18 mpg.

i will have to find that thread and post a link to it.

 

That is the uneven flame burn that causes detonation (pinging) in the combustion chamber. It's little explosions going on and are hitting the tops of the pistons and valves. A lot of reasons for this. Low octane fuel, high carbon deposits causing increased compression, to much timing advance, lean fuel conditions.

When the air/fuel is ignited in the combustion chamber, the burn should be smooth and quick which causes the pressure to push down on the piston. When this smooth burn is disrupted, the burn becomes eratic and causes detonation.