A few things that might be affecting your gas....
Your altitude. (CO?) No pro on this, but it must come in to play somehow.
Your driving style. Accelerating 4k lbs from s stop takes a toll.
Mods. Bigger tires/lift create more drag too.
Winter gas boils faster/sooner so it burns off faster. Cold start-ups REALLY take advantage of this at the cost of eating even more. I recommend block heaters in this case. Cold engines run harder to get to running temp, so they burn a HELL OF A LOT of fuel just idling. Typically, cars only need about 30 secs of start idle in the cold to be up and going, just don't hammer it. Let those fluids flow at a comfy pace.