Turning on the tow light

[Tom's LTZ]

So, today discoverd that when you turn on the switch for towing on the shifter it changes the shift points higher but also seems to keep it in V4 mode longer at about 35-45mph. Is this normal? sounds good when the motor stays in gear longer and just awesumed that the gas mileage would be worse but since it stays in V4 maybe its better. I have the 5.3 engine. Sorry for the dumb question!

[wandern]

Probably because the truck is not in an overdrive gear. Higher gear ratio = V4 has enough power to keep the truck moving at that speed. Still probably marginally worse gas mileage than running in V8 mode at 1250RPMs like it would do if it wasn't in tow/haul mode.

[Cap'n Pete]

Can you not verify your mileage running it in each mode, and see which shows better?