How to Get Better Fuel Mileage in a 6.6 Duramax

How to Get Better Fuel Mileage in a 6.6 Duramax

Calculating Your Baseline

If you own a Chevrolet or GMC heavy-duty pickup truck equipped with the trusty 6.6L Duramax diesel engine, fuel efficiency is likely a top priority. With fuel prices fluctuating wildly, every extra mile you can squeeze out of each gallon counts. But before making any changes to boost your mileage, it’s important to establish a baseline of your current fuel usage.

Resetting your vehicle’s trip odometers and carefully tracking the number of miles you drive between fill-ups allows you to calculate your real-world fuel economy. Simply fill your fuel tank to the brim, then drive as you normally would until you need to refill. Note the odometer reading and gallons required to fill back up. Then use this simple formula:

Miles Driven / Gallons of Fuel = Miles per Gallon

How to Get Better Fuel Mileage in a 6.6 Duramax

For example, if you drove 325 miles and it took 10 gallons to refill the tank, your fuel economy would be 325/10 = 32.5 mpg. Tracking this over several fill-ups will give you an accurate baseline against which to measure any mileage improvements from tune-ups or different driving habits. The factory average for the Duramax is around 22 mpg on the highway and 18 mpg in the city, but let’s see if we can do better.

Properly Inflate Your Tyres

One of the easiest and most effective ways to boost your fuel economy is to make sure your tires are properly inflated. Underinflated tires can lower your mileage by as much as 8% due to increased rolling resistance. GM recommends inflating the front tires on your truck to 30 psi and the rear tires to 35 psi when cold. However, many experts argue you can improve fuel efficiency even more by keeping tire pressure at the higher end of the recommended range, around 35 psi all around.

The small amount of extra effort required to check and inflate your tires regularly could yield significant savings at the pumps over time. Make it part of your routine maintenance to use an accurate tire pressure gauge at least once a month. Properly inflated tires also last longer and improve safety, so it’s a no-brainer to adopt this fuel-saving habit.

Use Two-Wheel Drive When Possible

Unless you’re towing or traversing tough off-road terrain, consider leaving your Duramax in two-wheel drive (2WD) mode as much as possible. The four-wheel drive (4WD) system uses extra fuel to continuously power the front differential and transfer case. Driving in 2WD or selecting the “Economy” drive mode if available helps reduce this parasitic loss and improves fuel efficiency as a result.

You may be surprised at how often you can get away with 2WD even on light dirt or gravel roads. Try it and see if you notice any handling or traction issues before reflexively engaging the 4WD. Even if it’s just for local errands around town, ditching the part-time 4WD function when not needed will boost your mileage.

Use Premium Diesel Fuel

While most diesel pickups will run on regular “clear” or #2 diesel, opting for premium #1 ultra-low sulfur diesel (ULSD) fuel can offer better fuel economy and power. The higher cetane rating of premium diesel allows for more efficient combustion in modern common rail engines like the Duramax. It also acts as a natural detergent, helping to dissolve and remove carbon deposits that can form over time and degrade engine performance.

Multiple fuel testing organizations have found that premium fuel can provide up to a 5% gain in fuel mileage compared to using regular diesel. The small extra cost at the pump is offset by higher efficiency. So for maximum diesel economy and longevity from your 6.6L Duramax, look for stations offering higher-cetane #1 ULSD when you fill up.

Change Engine Oil Every 6,000 Miles

Selecting the proper type of engine oil is critical to maximizing your Duramax’s fuel efficiency and service life. Synthetic oils are formulated to provide much better wear protection and help minimize oil consumption compared to conventional or blended options. Their low-friction properties also aid in sealing and help reduce parasitic losses.

GM specifies using full synthetic 0W-40 oil in the 6.6L Duramax, which requires changes every 6,000 miles under normal operating conditions. Sticking to the severe service change interval of 4,000 miles for conventional or blended oils is wise to prevent breakdowns in lubrication. For maximum fuel economy returns, religiously change to fresh full synthetic 0W-40 oil every 6,000 miles without fail.

Change the Air Filter Every 15,000 Miles

6.6L Duramax Diesel Engine - The Ultimax

A clogged engine air filter restricts the flow of oxygen into the engine’s cylinders. This damages fuel economy by limiting the amount of air available for complete combustion of diesel fuel. It also leads to loss of power and responsiveness over time. For best results, replace the air filter element at the recommended 15,000-mile interval.

Gently tapping dusty filters to dislodge debris before installing new elements also extends filter life. Visit your local auto parts store and stock up on air filters during sales to always have a clean replacement on hand. Taking just a few minutes every 15,000 miles to swap filters prevents restriction issues from creeping up and stealing fuel mileage gains.

Maintain DEF Fluid Levels

To meet strict emission regulations, Duramax diesel engines use selective catalytic reduction (SCR) technology. This injects a diesel exhaust fluid (DEF) into the exhaust stream to break down nitrogen oxides into less harmful gases before they exit the tailpipe. Maintaining proper DEF fluid levels is important to ensure maximum fuel efficiency from your SCR system.

The 6.6L Duramax calls for refilling the small DEF tank before the level drops below 5%. Allowing it to run dry can trigger a fault code putting the engine into reduced “Limp Mode” until serviced. Top up the DEF using premium diesel exhaust fluid every time you fill up with fuel to avoid any efficiency penalties. This simple chore could boost your mileage by up to 5% alone through cleaner burning.

Change Glow Plugs Every 100,000 Miles

The Duramax’s glow plug system plays an important role in heating the combustion chamber for fast, reliable cold starts. Over many heat cycles though, glow plug elements can fail prematurely due to carbon buildup or physical wear. Old, inefficient glow plugs force the starter motor to work harder on frigid mornings. They also reduce power and exhaust emissions at lower temperatures, which diminishes fuel efficiency.

Most experts recommend proactively replacing glow plugs every 100,000 miles as a preventative maintenance item. Doing so restores heater performance for easier starting and helps maximize your mileage year-round. The low cost is easily offset by fuel savings from a finely tuned combustion process, even in bitter winter conditions.

Change Brake Pads Every 30,000 Miles

Worn brake pads not only reduce braking power but also generate harmful vibration through the driveline. This parasitic vibration robs valuable horsepower, lowering fuel mileage over time. For maximum economy from your Duramax, change brake pads every 30,000 miles or when wear indicators show replacement is needed.

It’s also wise to replace rear pads in pairs rather than individually to maintain balanced braking forces. Having properly aligned, low-vibration pads prevents unnecessary stress on driveline components and frees up power usually lost to drivetrain shaking. This keeps your rig operating at peak efficiency between service stops.

Address Check Engine Lights Promptly

Ignoring the check engine light is never a good idea, as it could indicate an issue leading to decreased fuel economy, power, or increased emissions down the line. The Duramax engine control module is constantly running diagnostics to catch problems early. When a fault code is triggered, it pays to address the cause right away rather than waiting.

Even minor issues left festering can compound over time, potentially requiring more extensive repairs. Nip potential problems in the bud by taking your truck to a trusted diesel shop for a diagnostic scan within a day or two of the light appearing. Quick intervention avoids bigger headaches and mile-robbing inefficiencies later on. Your fuel mileage will thank you!

Avoid Excessive Idling

Banks TurnKey Engine Program - Banks Power

While occasional idling to warm up on frosty mornings makes sense, extended unnecessary idling wastes fuel. According to the U.S. Department of Energy, an engine burns over 1/2 gallon of fuel per hour when left idling. Always shut off your 6.6 Duramax if you’ll be stopped for more than just a few minutes whether in traffic or a drive-thru. You’ll be amazed at the gallons saved over months or years through this simple yet often overlooked habit.

Exceptions include especially cold subzero weather when short warm-ups are needed for safety and extreme heat, to keep the interior comfortable before driving off. But strive to keep overall idling periods minimal for noticeable fuel savings without compromising comfort or convenience. Every gallon conserved at idle goes further on the open road!

Moderate Air Conditioner Use

On hot summer days, blasting the air conditioner feels fantastic inside the cab. But running full-blast AC also requires extra effort from the engine to power the compressor, which can lower your mileage up to 20% on the highway and even more in stop-and-go traffic. For maximum efficiency, only use the A/C when truly needed and set the temperature no lower than 72°F.

Consider opening windows instead on cooler days or when moving below 45 mph. You’ll arrive just as comfortable while allowing the Duramax to breathe easier. If hauling or towing heavy loads in hot weather, the cool airflow is a must. But for daily drives without a payload, moderate AC usage helps significantly boost efficiency.

Regular Dealer Maintenance

Staying on top of routine inspections and services at the recommended 15,000-mile intervals catches small issues before they impact fuel economy or require expensive repairs down the road. Dealership technicians thoroughly inspect fluid levels, belts, spark plugs, filters, brakes, and other worn items to ensure your Duramax runs at peak efficiency.

General maintenance items like coolant, transmission, transfer case, and differential fluid changes are all timed to maximize the service life of components. Proper lubrication protects your investment while maintaining low friction for higher mileage. Trusting your vehicle’s maintenance to factory-trained pros pays off fuel savings and durability in the long run.

Combining Tips Adds Up

Implementing several of these fuel-efficiency techniques together produces even better results. Tracking baseline mileage, keeping tires inflated, using premium diesel fuel, and minimally idling nets noticeable improvements before any modifications. Committing to proactive maintenance and addressing issues promptly prevents bigger problems. With smart driving habits and regular care, many Duramax owners report an average combined city/highway fuel economy of over 25 mpg.

By combining inflation checks, premium fuel, efficient driving techniques, and maintenance, you should easily surpass the EPA estimates and manufacture averages for this impressive diesel truck engine. The small costs are offset many times over by savings at the pumps, freeing up funds for fun adventures down the road. With a little diligence, the always-welcome extra fuel mileage from your 6.6L Duramax can become a reality.

FAQ: Best Upgrades for Duramax Mileage

For those seeking even greater efficiency, bolt-on modifications and powertrain upgrades exist. However, professional installation is recommended to preserve warranty coverage if still in effect. Top options include:

  • Intake/exhaust optimizations like cold-air intakes and tuned exhausts boost power 1-5%, slightly improving highway mileage.
  • Performance programmers/tuners aim for fuel/timing curves for extra towing power but potentially lower city mileage.
  • Higher-flow filtration like luber-finer or K&N products may gain 1-2% through reduced restriction.
  • Removing weight improves mileage in all driving conditions. Consider a lighter bed cover over the standard topper.

While mods require research, the lowest-hanging fruits remain diligent maintenance and hypermiling techniques for guaranteed OEM+ fuel efficiency gains. Bolt-ons should complement, not replace, solid driving habits.

FAQ: Effect of Turbo on Mileage

Larger or upgraded turbochargers don’t directly impact fuel economy on their own. However, more boost may slightly boost highway mileage potential through added torque for cruising. The extra power also allows for maintaining speed on grades versus downshifting.

But bigger turbos often come at the expense of idle power and response, hurting city mileage where stop-and-go driving occurs. Extra under-hood heat also stresses other components over the long haul.

For dedicated highway cruisers, a mild turbo upgrade tailored for highway speeds could yield marginal mileage benefits. But for mixed or in-town use, benefits are unclear – proper tuning for all operating conditions is critical. Stick to OEM for maximum well-rounded efficiency.

FAQ: Effect of Removing Muffler on Mileage

Removing the factory exhaust muffler provides no benefit to fuel economy and likely decreases it slightly through altered backpressure. Louder, less restricted exhaust Flow may feel slightly smoother but provides minimal if any additional power.

The benefits are purely audible, not functional. However, changes to tune or component sizing to compensate for muffler removal introduce the potential for reduced low-end torque and idle stability, both harmful to fuel economy.

Unless performed with a comprehensive tune by an experienced shop, muffler deletion tends to damage efficiency. It’s best left to enthusiasts to prioritize sound over mileage. Stick with stock exhaust for maximum fuel savings from your Duramax 6.6L engine.