Duramax to 6.6/10spd Gasser

CRApex · June 15, 2023

I've been holding off on sharing my thoughts until I had enough miles on my new truck to formulate an opinion. Here's some background: my previous truck was a 2020 3500 SRW High Country 4wd with the Duramax. I've been driving Duramax trucks for the last 15 years, so I'm very familiar with their capabilities. My new truck is a 2024 3500 SRW High Country 4wd with the 6.6 Gas/10spd combo. The only difference in options is the 2024 has a sunroof and the 2020 did not. The sticker price on the 2020 was just over 76k, and the sticker on the 2024 is $77,540.00. I've put just under 3000 miles now on the new truck.

Let me get this out of the way right up front: I really liked the Duramax. There is no comparison in power, and in no scenario will the 6.6 gas/10spd compete with the Duramax for power. Torque is king when it comes to towing. That said, the 6.6 gas/10spd does get the job done. I've towed just over 10k (the same trailer I towed with the Duramax many times) and this is my comparison since I'm very familiar with it. The biggest discrepancy I've noticed is passing power. I'm learning to adjust my expectations on how much space I need to complete a pass. I don't want to come off as I think the truck is a slouch because it's not. I'm very impressed with the combo and how it seems to stay in the power band. I haven't noticed any violent downshifts to keep the load moving. The gasser seems to hold the speed very well, even on moderate hills. I'll update more on this once I get some more miles and towing under my belt.

Driving around unloaded, the gasser is great. The transmission shifts great. My response to others that have said the 10spd is a bit busy is that it's related to the tranny learning early on. I had a little of that at first, but it's already smooth as silk. Additionally, it seems to be getting more powerful. I'm not sure if that's just me getting used to the feel of the truck or if it's reality. I haven't done any scientific 0-60 runs. Now onto mileage. I've read reports from gas owners claiming up to 20MPG's. I don't see that ever happening and I'm not sure how that would even be accomplished short of driving downhill with the wind at your back everywhere you go. The best I've seen is 17 with an average (on the DIC) of 11.4. A full tank shows a range of around 550 miles. The Duramax would sometimes flirt with a 700-mile range. Maybe the 6spd was better for MPG's? Maybe the 10spd will go up once the truck loosens up a bit. We'll see.

Bottom line: I really like this truck, and it has plenty of power to handle whatever you need it to. This post was more for any current diesel owner considering the switch to gas. You just need to adjust your expectations. What you give up in towing power, you gain in cheaper fuel, and knowledge that you are driving the most reliable version of the GM HD (even though I had minimal issues with the Duramax). BUT this gas/10spd combo will get it done. Plus, with how crazy expensive these trucks are getting, you save $9390 by sticking with the gas motor. Lastly, you get to avoid the filthy diesel pumps, dragging diesel into your truck where the previous guy managed to spill a gallon of fuel and filling up DEF.

XY74 · June 15, 2023

I have toyed with the idea of trading in my 2020 diesel HC and going back to gas. But....... I still have it and still like it a lot!

Michael Ross · June 15, 2023

Thank you very much for that information. Exactly what I was looking for.

UWSkier · June 16, 2023

Super helpful. I'm cross-shopping GMC and Chevy 6.6L gassers this weekend and it sounds like that powertrain will do exactly what I need it to do.

nards444 · June 16, 2023

I would echo your exact sentiments, have had many diesels, and had a 21 Chevy 2500 diesel and traded in for a 2022 2500 Gasser. In a way I was let down but let me explain. As far as breaking, handling etc there will be no differences, short of the diesel does have the exhaust brake which helps. And however you cut it the gasser will never compare, ever. My main let down is passing especially while towing, there are times now specially on two lanes that I just cant pass in the gasser. Theres also setting the cruise at 78mph and going up hills in TN hauling a 6k boat and with the diesel I was passing people on the interstate and the diesel wasn’t breaking a sweat, but you are not doing that in the gasser. The gasser I also feel like is a lot less responsive in just regular in and around then the diesel and even half tons I have had.

Conversely with the gasser its 10k cheaper and fuel is about 1.25-$2 cheaper a gallon over the last two years, although the diesel did get 20-30% better mpg, the gasser was still cheaper. With diesel not all stations have it, it stinks and just requires more filter and maint, you go from $75 oil changes to double or more than that. But like you never seeing sustained 20mpg in the gasser, no way no how, although did see it in the diesel a few times in ideal conditions.

For me my main thing is hauling around a 6k boat 3-4 months out of the year 90% of the time 20min away, but max would be an hour away, with no hills, and then utility trailer with various things on it. But really just want a truck that I could throw or haul anything I wanted that most average guys would do, and the gasser does that. In my situation because of the 10k upcharge on the diesel I was able to trade it in, which was a highly optioned LT and an AT4 gasser for really the same money, did debate getting an LT level gasser and saving money, but for a more bucks a month I went with the high option. End of the day hauling around a boat 10-12 times a year just didn’t justify the added cost of the diesel, im saving 75 bucks a fill up a week, do the math, plus cutting of maintenance.

With that said if I was retired doing lots of interstate hauling and so forth, theres no way I wouldn’t be in a diesel as the gas set up is really inferior by a wide margin.

UWSkier · June 22, 2023

Based on this post and the towing report by @the8rotor, I pulled the trigger today. Gonna miss my "little" half ton crew cab. This thing is enormous...

Will report on towing the boat and RV once I get a few miles on.