The Best After Market Device for Increasing Diesel Mileage – You’ll Need it When Diesel Goes Back Up Again

Which of the many after market mods will increase your diesel fuel mileage?

Even though, on average, diesel engines get better fuel mileage than gasoline engines, there have been many after market devices introduced for increasing diesel mileage. Do any of them even work? If so, what is the best device for increasing diesel mileage? That is a question many drivers want answered, and even more will be clamoring for an answer to that question if fuel prices continue climbing.

Some of the recent proposed congressional legislation promise to push fuel prices even higher, in the name of cutting back on greenhouse gasses. The more fuel costs, the less people drive, and the less carbon comes out of the tailpipe. The strategy will doubtlessly be effective, as the high fuel prices in the summer of 2008 caused people to tun to fuel efficient vehicles in droves. Those higher fuel prices will almost force motorists and business turn toward more fuel efficient vehicles, or modify the ones they already own to get better mileage.

The other factor effecting fuel prices is that increasing the domestic supply is frowned upon for environmental reasons, leaving U.S. Citizens to depend upon an increasingly volatile region for the bulk of it’s oil supply. Business hates uncertainty, and that is reflected in higher oil prices. Rest assured, you will pay more for diesel in the not too distant future.

Many modern diesels, especially those found in trucks lie the GM Duramax, Ford Powerstroke, and the Dodge Cummins diesel produce prodigious amounts of torque right off the showroom floor. The problem for truck owners is the mileage sin’t all it could be. Much of this can be traced to steps undertaken by the manufacturers to curb emissions from the big diesels. While they produce tremendous amounts of torque, the torque peak is shifted higher in the RPM range than it should be for optimum efficiency. This is done in an effort to combat tailpipe emissions, but consequently these trucks get about 15 – 20% worse mileage than they should for many drivers.

With cars like the Volkswagen Jetta TDI diesel routinely getting over 45mpg, their drivers are already well ahead of the typical motorist in terms of fuel economy, unlike the aforementioned truck pilots. You can always improve things, and owners of large diesel pickups or 18 wheelers are constantly looking for ways to improve their mileage. In many cases the drivers of such vehicles are using them to earn a living, and every dollar spent on fuel comes straight out of their bottom line. Even if you’re just using your Cummins powered Ram to tow your boat or travel trailer on weekends, saving a bit of fuel is always welcome. If the price of diesel fuel starts heading up over $4.00 a gallon again, it will become essential to find ways to get your diesel better fuel economy.

The question is, how much can the mileage be improved? The easiest and cheapest fuel saving modification you can make is to your right foot; lighten it up a bit. It won’t cost you a cent, but can definitely return a savings at the pump. Why is it so important to keep your weight off the right foot with modern diesel engines?

It all comes down to one thing; boost pressure. Modern diesels are turbocharged, which does wonders for their power and efficiency. A side effect of turbocharging however, is that when you dip into the throttle, the boost pressure goes up, causing a massive power surge. Unfortunately for the mileage minded among us, it also tells the ECU to increase the injector’s duty cycle, so the engine gets the extra fuel it needs to keep up with the air forced into the engine by the turbo. Extra fuel in means worse mileage out for your diesel.

So short of driving like GranMaMa, what after market goodies can you add to your diesel powered rig to bring out it’s parsimonious qualities? Probably the easiest and most cost effective add on is going to be a low restriction intake system. This is simply a smoother, more direct shot from filter to intake manifold, rather than the somewhat convoluted path the factory sets up for the air to travel on its way into the engine. At the entrance there will be a low restriction air filter. By freeing up the engine’s ability to pull in air, this device will increase not only mileage but also power and throttle response.

What a bonus! Low restriction intakes are made by many performance oriented after market manufacturers, such as Bully Dog, Banks Engineering, and K&N. They are fairly inexpensive, ranging from about $200 up to the $400 range. All in all an intake is a pretty cost effective mileage modification. You might see up to a 10% mileage increase with the addition of an intake, but you’ll also hear more noise from the intake tract.

Be careful if you use an oiled filter, as some people have reported problems with their MAF (Mass Airflow Sensor) units due to excessive oil leaving the filter and coating the MAF. Properly oiled, this shouldn’t be a problem, and I have used a reusable, oiled K&N filter myself for over 125,000 miles without a hint of trouble. You should just be aware the potential for problems exists.

Speaking of noise, you’ll find the other cost effective mileage mod dedicated to getting things out of the engine, and it will definitely increase the noise level a few decibels. A high performance, low restriction exhaust system will help increase your diesel mill’s efficiency. Like the intake, you’ll gain on both ends of the spectrum, picking up some power and torque, along with your gain in MPG. How much of either you’ll get depends on the exact system you install.

Another exhaust related mod that is fairly popular is the DPF elimination kit. DPF stands for Diesel Particulate Filter, and is an integral part of the emission control system on trucks made since 2007. As the name suggests, it’s job is to filter particulates out of the exhaust. That’s why most modern diesel engines don’t smoke like a factory from the Civil War era. As the DPF fills up with trapped particulate matter, the emission control system uses one of several ways to clean it out, restoring the flow.

The process of burning out the stored particulates is called regeneration, or regen for short. Your engine will monitor sensors in front of and behind the DPF to measure pressure differential between the front and rear of the filter. When the number exceeds a factory specified parameter, you get all manner of fun. The idle speed increases (keep your foot firmly on the brake when stopped in one of these vehicles, lest a sudden increase in idle speed send you nosing ahead into the car in front of you. It’s great fun at the Mikey D’s drive through.) and you’ll see some light colored smoke out of the tailpipe as the old soot burns off.

There are two problems with the DPF. Problem one is that even when the flow is restored to as-new levels, the DPF still provides a restriction in the exhaust system. Number two is that the regen process uses extra fuel when it happens, usually every 150 – 500 miles, further decreasing your fuel mileage. By eliminating these two problems, a DPF elimination kit will increase your diesel mileage, and as with a performance exhaust system, add some power as part of the bargain. Unfortunately when you eliminate the DPF, you’ll also eliminate something else in most cases, your vehicle’s warrantee, and your pristine exhaust.

In addition you’ll run afoul of the all-powerful Environmental Protection Agency, which is why these devices are only to be used off road, not to increase your mileage when towing your boat to the lake. The nice thing about eliminating your DPF is that it is a cheap and effective strategy, and who doesn’t like those? The not so nice thing is that it turns you from law abiding into a law breaker and voids your warrantee, so install one at your own risk.

All modern internal automotive and light truck engines are controlled by computers that would put those used by NASA for their 1970’s space missions to shame. They have reign over virtually every system in your vehicle, from engine and transmission operation to keeping you at a comfortable 72 degrees while you enjoy The Herd on ESPN Radio, courtesy of Sirius/XM. The computers in question are called Electronic Control Units (ECU) or Electronic Control Modules (ECM). In a diesel engine they control the injectors and the turbo boost, in addition to the transmission shift points, slippage, and torque converter lockup. You can see they have a huge potential to affect the mileage and power your truck puts on the road.

In the beginning, ECU modifications (also known as an ECU flash and an ECU remap) were mainly targeted toward increasing power and torque so drivers could improve their acceleration and comfortably tow big loads. Then the auto manufacturers started boosting power on their trucks, so that right off the showroom floor many trucks had over 600 pound feet of torque. That’ll pull your horse trailer! Right about the same time diesel prices went from less than $2.00 a gallon to over $3.00per gallon. Suddenly, increasing mileage was a much higher priority for drivers, especially as their trucks were so well endowed straight from the factory.

The upshot of this was that many of the aftermarket ECU manufacturers started developing devices that were targeted at increasing fuel mileage, rather than boosting power and torque. In most cases they actually did a bit of both, however. Some of the better known and more reputable after market performance chip tuning brands include Bully Dog, Banks Engineering, Hypertech, Superchips, Edge, and Jet. Most of them are adjustable, so you can vary your tuning according to your specific needs. That way when you are doing heavy towing through the hills, you’re not running the same ECU set up as when you’re driving in traffic in the valley.

Some will also let you check or reset your trouble codes. That’s nice because you can see what is up before you spend the time and money to visit the repair shop. Another advantage is that since they control the transmission, you can change the shift points to help increase your mileage, and firm up the shifts. Firming up the shifts will increase transmission clutch pack longevity, acceleration and fuel mileage, all at the same time.

There is actually a distinction between the types of ECU mods. You can get a new, reprogrammed ECU or install a device that simply attaches to the existing wiring harness and changes the program of the existing unit. These add on units are also known by the moniker programmers, performance programmers, or some such nonsense.

Some of names used by the mileage enhancing ECUs are MaxEnergy (Hypertech), Mileage XS (Superchips), and MileageMax (Edge).

Do they work to increase mileage? With the newer diesels many people report getting an overall 2 – 4 mpg increase, in addition to the increased power and response they enjoy. Obviously, that will depend a lot on driving conditions and how deep you depress the accelerator. Given that the after market ECUs are so easy to install (just a simple unplug the old, and plug in the new in most cases. Some of them also “piggyback” on the old ECU, which is what I was describing above) it is a pretty nice mod. In most cases the install takes all of 20 – 30 minutes, and you don’t even have to get your hands dirty!

If you’ve added other performance parts, such as air intakes or exhaust components, you’ll likely see a bit more improvement than installing an ECU upgrade alone.

On an MPG per dollar basis, and ease of installation basis, plus given the fact that it adds substantially more power on turbocharged diesel engines, while simultaneously increasing power and torque, the performance ECU has to be the best after market device for increasing diesel mileage.

Most of the reputable ECU manufacturers make a good product, but the MileageMax from Edge seems to give the best bang for the buck, since it is about $50 – $100 less expensive than the others. To find out more, and see what customers who bought the Edge and other performance ECUs have to say – click here now.

Stay tuned for some modifications to increase the mileage (and maybe power) on diesel cars, such as the VW TDI diesel.

3 Responses to “The Best After Market Device for Increasing Diesel Mileage – You’ll Need it When Diesel Goes Back Up Again”

  1. Thanks for the tips, my being in CA a leader in smog regulation, makes it tougher to add aftermarket devices, though at least in this state diesels are exempt from the bi-anual smog/quipment test/inspection.
    It;s quite impressive to see the advances VW, Audi, etc manage to mske with the dinosaur diesel technology.

  2. W T

    I want to get the edge in my truck but I didn’t know that it would help my gas mileage. Is that really true that I can get more horsepower and increase mileage. It sounds too good to be true. I also wanted to know if I get a new muffler and a larger exhaust will that also increase my horsepower? I love my dodge cummins but it is kind of slow off the line. I want to go to bend truck repair as they seem like the most knowledgable in my area.
    Thanks

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