Reads more like pre-detonation, fuel mixture in the cylinder is igniting from heat just before spark plug fires, often called "pinging", what you hear are the two "explosion" wave fronts meeting inside the cylinder.
Going to a higher Octane would lessen "pinging" but not lifter noise.
Using a 10% ethanol mix also raises octane.
An Octane number is a heat range number, the higher the number the higher the temperature it takes to self-ignite it.
The 3.0l engine can run on regular gas, 87 octane, without pinging, so my guess would be the EGR system might be getting restricted or you are getting carbon build up in the cylinders.
Since all gasoline has the same energy per gallon(octane is a heat number) getting better MPG and performance would mean you probably can't hear all the pinging.
Pinging robs an engine of power since part of the fuel mixture is wasting power pushing against the other part instead of pushing the piston down.
An engine designed to run on 87 octane will get the exact same MPG and power if 93 octane is used, laws of physics not my opinion, lol.
Ethanol has less energy per gallon, so a 10% mix might lower MPG by .5MPG, and no power difference should be felt.
EGR(exhaust gas recirculation) system is used when engine is under load, when you give the engine more gas the cylinder temp will start to rise up, this produces extra emissions because of the heat, circulating exhaust gases back to the intake manifold reburns some of the emissions but ALSO cools the cylinder, reducing emissions and possible "pinging" from the heat buildup.
If EGR tube or valve start to get build up inside then the amount of exhaust gas is restricted, so engine could start to ping when it didn't before using the same octane fuel.
Carbon build up is not common but often heard of with the 3.0l.
When engine runs a bit rich or is not driven for 20 minutes each time it is started you will get partially burned fuel build up inside the cylinders, this is carbon build up.
The carbon layer can do three things to cause pinging.
1. It can absorb some of the fuel in the fuel air mix, making mixture lean, lean mix = ping, because it self-ignites with less heat
2. carbon layer holds heat in cylinder and can cause a hot spot, that will cause pinging under load as it heats up more.
3. Carbon layer increases compression slightly in the cylinder, the higher the compression the hotter the fuel/air mix gets during compression.
This is why high compression/high performance engines must run higher octane, they don't get more power from higher octane, octane is about heat not power, they have to use higher octane to prevent pinging.
I would pull a few spark plugs and look at the tips, black residue is a sign of carbon build up.
There are ways to clean carbon from cylinders without taking engine apart, I haven't done that before so I can't recommend any specific method, but be careful you can damage engine if done incorrectly.
It might be worthwhile to try a live OBDII reader while driving and get a few numbers from the sensors.
You could also just be running a bit too lean when accelerating which as said above will cause a ping.
Last edited by RonD; 01-18-2014 at 01:24 PM.