Gas Type?

[Texas Red]

I've used only 87 for 65000 miles in my 2003 model, no problems. A friend has an Escalade with the same 6.0 Vortec and it clatters on 89. The H2 was tuned for 87 and that is what my 2003 manual recommends (as I recall).

running Chevron regular in my H3 (owners manual recommends regular)

[HUMTECH]

You only need 87 octane. Higher octane fuel is for use when combustion chamber pressures are higher like when you add A supercharger. Octane is not A performance additive, rather it raises the fuels resistance to burn to prevent preignition in higher compression motors. If you use low octane fuel in A higher compression motor the fuel will ignite prior to the sparkplug firing causing pre-ignition/detonation from the pressure in the cylinder. No advantage to using A high octane fuel in A low compression motor.

[mikejr]

running regular 87 in the H2, no knocking and runs like a champ.