⚠️ LEGAL DISCLAIMER: OFF-ROAD USE ONLY
The following content discusses the removal of emissions equipment, which is intended solely for off-road competition use. Modifying emission systems is illegal for street use in the United States and Canada.
Author: Lawrence Z, Diesel Performance Specialist at DPFexhaust
If you use your 2016 Chevy Silverado or GMC Sierra 2500/3500 HD (LML) to haul a heavy 5th-wheel RV or gooseneck trailer, you likely stare at your fuel gauge in frustration.
Stock LML trucks are notorious for poor towing fuel economy—often dropping into the 8–9 MPG range when pulling 12,000+ lbs. The culprit isn't the engine's capability; it's the emissions system.
The "Regen" cycle dumps raw diesel into your exhaust to burn off soot, and the restrictive DPF chokes the turbo.
You want to know: "If I delete my truck, will my towing MPG actually improve?"
Here are the honest, data-driven results and the specific setup you need for heavy towing.
1. The Real Numbers: What MPG Gains Can You Expect?
Let's cut through the forum hype. You will not double your mileage while towing a giant box against the wind. Aerodynamic drag is a law of physics that a delete kit cannot change.
However, by removing the regeneration cycle and allowing the engine to breathe, you can expect significant, measurable gains.
| Driving Scenario | Stock LML MPG | Deleted LML MPG (Tow Tune) | Realistic Gain |
| Unloaded (Highway) | 14 - 16 MPG | 18 - 22 MPG | +4 to +6 MPG |
| Towing 5th Wheel (Heavy) | 8 - 9 MPG | 10.5 - 12.5 MPG | +1.5 to +3 MPG |
The Verdict: While +2 MPG sounds small, when you are towing thousands of miles a year, that is a 20-25% reduction in fuel costs. Plus, you completely eliminate the cost of DEF fluid.
2. The "Tow Tune" Factor: Why Max Horsepower Kills MPG
To achieve these gains, you cannot just load a "Race" tune. For towing a 5th wheel, you need a dedicated Tow Tune.
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Timing & Efficiency: A proper Tow Tune adjusts injection timing to maximize fuel atomization at lower RPMs (where you tow), rather than just dumping fuel for peak horsepower.
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Turbo Braking (Safety): This is critical. The 2016 LML has a Variable Geometry Turbo (VGT). A good Tow Tune utilizes the VGT vanes to create aggressive Turbo Braking (exhaust braking) when you let off the throttle. This saves your service brakes on long descents—a safety feature you cannot afford to lose.
3. Protecting the Allison: TCM Tuning is Mandatory
Your 2016 LML comes with the legendary Allison 1000 transmission. While robust, it is tuned from the factory for "slushy," comfortable shifts.
When you delete and add power to improve MPG, you must tune the Transmission Control Module (TCM).
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Lockup Strategy: A TCM tune will lock the torque converter earlier. An unlocked converter slips, turning fuel into heat (wasted energy). A locked converter turns fuel into forward motion.
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Result: More power to the ground = Better MPG. If you skip TCM tuning, you are leaving fuel efficiency on the table.
4. The Hidden Benefit: EGT Management
Improving MPG is great, but keeping your engine alive is better.
When towing a 5th wheel up a grade, a stock LML's EGTs (Exhaust Gas Temperatures) can skyrocket as the DPF restricts flow.
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Deleted Flow: With a 4" or 5" straight pipe, there is zero backpressure. Heat escapes instantly.
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The Result: Your engine runs 200°F - 300°F cooler. This allows you to pull hills with confidence, without backing out of the throttle to save the engine.
Summary: The Perfect Towing Setup
To improve your 2016 LML's towing MPG and reliability, don't just buy a "cheap pipe." You need a system engineered for hauling.
Your Shopping List for Max Towing Efficiency:
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Exhaust: 4" Stainless Steel System (Best balance of flow and low drone).
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Tuner: EFI Live with Custom Tow Tunes (Specifically requesting Turbo Braking).
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TCM Tuning: To lock that converter and save your clutches.
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Configured specifically for 5th-wheel haulers who need MPG and safety.
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