Have a few friends who have either owned or sold their 3.0 Duramax (2020+ Silverado or Sierra) due to a bunch of issues with the EGR, DPF, and emissions systems, and others that say "it's been a perfect truck with 30-33MPG highway and zero hypermiling". Since I tow trailers, and do concert promotion work, I am thinking of a baby Duramax as a "tow-only" vehicle which even with a trailer, should get double the fuel mileage of a gasser. Any downsides to a 3.0 Duramax being used for occasional (non-daily) use but regular towing? Some friends say to get a gasser, some say the diesel is fine, and others say it is only good for 30-33MPG unloaded, tow mileage will be the same as a 1/2 ton. What gives? These things are selling for less than comparable gas 1/2 tons, but I would have to go down South to get the best deals: https://www.alwaysmotors.com/inventory/gmc/sierra-1500-crew-cab/444836/ https://www.cavenderautogroup.com/inventory/used-2020-gmc-sierra-1500-slt-rwd-4d-crew-cab-3gtp8det0lg280231/ https://www.group1acurasouthwesthouston.com/inventory/used-2020-gmc-sierra-1500-slt-rwd-crew-cab-pickup-3gtp8det1lg257525/ Example of one of the trucks that's reasonably priced and seems to be well-kept for 133k miles.
Looking for answers to a little diesel on a hybrid forum? Kinda unusual - but here's some of what I find.; Thrust Bearing / Crankshaft End Play Failure (Primarily 2025–2026 LZ0 Engines) This is currently the most severe and widely discussed issue. Some 2025 and 2026 LZ0 engines experience premature thrust bearing wear or manufacturing defects, allowing excessive crankshaft movement ("end play"). Symptoms include a rattling or knocking noise from the bellhousing area (near the torque converter/flexplate), low oil pressure warnings, illuminated check engine light, and DTC P06DD (engine oil pressure control valve performance). In worst cases, it leads to catastrophic engine failure ("grenading") at very low mileage—often under 10,000 miles, with reports as low as 1,000–5,000 miles. GM has issued TSB 25-NA-307 for diagnosis (checking crankshaft end play), but as of early 2026, no full recall has been issued despite multiple engine replacements under warranty. Dealers have reported clusters of these failures. GM is monitoring it, and some owners note good warranty support for replacements, though downtime and parts backorders can be lengthy. This appears linked to specific build dates; later production may have improvements, but caution is advised. Oil Leaks (Especially Rear Main Seal) Rear main seal leaks are frequently reported, sometimes at low mileage, leading to significant oil loss. Fixing it is labor-intensive because it typically requires dropping the transmission. Other oil leaks from various seals or gaskets are also mentioned. These can appear on both LM2 and LZ0 versions. Long Crank / No-Start or Hard Start Conditions A persistent complaint, especially on earlier LM2 engines (2020–2021/early 2022). The engine may crank for an extended time (10–20+ seconds) or fail to start intermittently. Common causes include a faulty or bent camshaft position sensor exciter/trigger wheel (which can contact the timing chain), issues with the high-pressure fuel pump, or other sensor/electrical gremlins. GM has released multiple TSBs addressing this. It can be frustrating and sometimes requires major disassembly (in extreme cases, cab-off or engine-out work). Emissions and DEF System Problems Like most modern diesels, the 3.0 Duramax has a complex emissions setup (EGR, DPF, SCR with DEF/urea). Owners report: DEF sensor failures, clogged DEF injectors, or pumps leading to "Service Emission System" warnings and limp mode. Frequent or excessive regens. Check engine lights tied to NOx sensors or EGR issues. These can be more annoying than catastrophic but often result in dealer visits, software updates, or part replacements. Some note the system is sensitive, and DEF quality or usage (especially when towing) can exacerbate problems. The LZ0 version pulls EGR gases post-DPF (cleaner), which helps reduce intake/EGR clogging compared to competitors, but issues still occur. Oil Pump Drive Belt Concerns The high-pressure oil pump is driven by a rubber belt (wet belt in the oil sump) rather than a chain. GM originally projected a 150k–175k mile interval, later adjusted (some say to 200k on LZ0). Owners and mechanics criticize this design for the potential of sudden failure (leaving the engine without proper lubrication, which is disastrous for a diesel). Rather than get the straight six from GM, the most trouble free little V6 comes from Mercedes, like what goes in the Sprinters. We had that configuration in our class C motorhome and it could easily pull a car in addition to its own weight with Grey & black tank full ..... uphill Our pickup has the bigger 6.6L for pulling our 5th wheel. Deadheaded from Northwest Montana to Nashville and got 25 MPG. Pulling the 5th wheel? 9¾ mpg. That's why around town - will either take the plug-in minivan or the e-bike.
@hill, thank you for the detailed reply. There were a bunch of people on the Volt forum that had these, hence why I am asking a group of non-biased individuals. Duramax owners tend to be very loyal, similar to Tacoma and Jeep owners, that often skew the "I've never had an issue with my truck" to really mean "replaced the EGR, entire DEF system, injectors, and a transmission at 100k, but the truck is perfect" lol I will still drive my Prius Prime for commuting and pretty much walk, bike, or shop local (even groceries I get from in-town, despite it being a 20 minute walk back and forth).
As someone who worked with a fleet of diesels I'd say that the thing about diesels is a lot has to do with how and where they're driven. A diesel that's driven on mostly long, flat, warm highways will often not have hardly any engine problems at all. You get less particulate matter in the filter and on the backs of valves, and you get more engine heat to help burn off the PM that does get in the filter extending the time needed for regens. You also need less DPF as you're creating less NOx naturally too. And you're keeping the engine away from the two extremes that do the most harm to the mechanical parts and the emissions equipment: idling and full throttle. But if you drive short distances, have lots of hills, drive a lot in stop-and-start traffic, and have lots of cold weather, then you're clogging the particulate filter, needing constant regens, getting more suet build up, and chugging DEF. Then you add to that the drivers that think "this is a diesel, so I need to idle the &%@! out of the engine." That's just plane engine murder. Other than for needed regens, idling only hurts modern diesel engines. It creates suet that isn't easily burned off. Then the engine needs even more regen cycles, and that's always when the driver decides he doesn't want to idle his engine. So then you end up with this cycle of idling when it shouldn't be idling and not idling when it should be idling, which wreaks mayhem on the poor engine and its emissions equipment. Instead, you can try to not idle the engine as much as possible (unless needed for regen), try to give the engine a steady load everywhere you go, instead of flooring it because you really want to have a sports car, and perhaps wrap the exhaust components with thermally insulated exhaust wrap to keep them as hot as possible. Those things can help tremendously in extending the life of your engine and emissions components and reducing the need for regens and DEF.
