Oh ok. I had the initial impression your truck was a bit older, but yeah, no, you're not significantly lighter, than the gas powered 2500s and 3500s. You are significantly lighter than a diesel quad cab 4x4, but only if your a regular cab 2wd gas job. Your ratio would probable be 3:43, 3:08, 3:23, something like that, you don't get lower than 4:10 in a half ton generally, and even that's rare. The cylinder shut off was annoying joke, they quit doing that for a reason, it's really problematic and it takes the same amount of energy to move a certain vehicle a certain distance at a certain speed, regardless of 4 or 8 cylinders. Engines of different manufacture do use different amounts of fuel to do the same thing, not denying that. GM set up a scenario where you could see in real time if the exact same specced vehicle would get better mileage with four or 8 cylinders working. they didn't. I bet you get around 17-19 mpg, which is been the chevy v8 standard average milage for a roughly 5.5 liter v8 powered pickup with a rear end ratio somewhere around 3:40, since 1970. I know you do get better mileage than when the cylinders are fully activated, but, they only activate when they're needed, so, its kinda more marketing than anything, you'd get good mileage all 8 activated and not working harder too. GM is famous for shit like this, their old 4 barrel carbs with the tiny primaries and massive secondaries just lead to the secondaries opening ALL THE TIME, which resulted in worse mileage than a big 2 barrel carb or a equal bore 4 barrel. nevermind they were at the same time putting 800 cfm carbs on motors did better with 500, raised vacuum is beneficial, because people saw "800 cfm" as "just like my drag racing heroes". A significant part of corporate engineering is marketing driven. you never need bigger than 500 cfm unless you have an 8 liter ish motor exceeding 7000 rpm, or some sort of forced induction.