Back in the day when this bad Boss 429 was roaming the streets, some of the gas saving tips held true, but not anymore.

Your EGR is an integral part of your emission control system. EGR stands for Exhaust Gas Recirculation and it does exactly as the name suggests; recirculates some of your exhaust gas back into the intake manifold, where it mixes with incoming air. This helps lower combustion temperatures and as a result, decreases oxides of nitrogen (NOX) emissions.

Many people believe that plugging the EGR or bypassing it will in some way increase their gas mileage and give them a few more precious horsepower. Can simply bypassing the EGR give you better gas mileage? Can it be that simple?

No, it can’t. In modern engines, you will actually stand a better chance of losing a few percent in the MPG department, rather than making any gains. You really gain nothing by bypassing it. Your car actually does it for you under acceleration, when an EGR block swings into action to prevent it from functioning. So if you have a modern gasoline engine, forget the notion of saving a little bit of precious unleaded by just bypassing your EGR. It doesn’t work.

What about some other easy ways to get better gas mileage you may have heard about? You can always drive slower,but how much fun is that? No, I’m talking about tricks, like the 100mpg carburetor or the magnetic fuel molecule aligner. More to the point I’m talking about things that have been long reported to save gas, but actually don’t.

The first thing on the list is a having a clean air filter. That mileage myth has some basis in fact, but it no longer holds true. In the past, back in the glorious days of Holley double pumpers or Rochester Q-jets, a dirty air filter could cut back on your power and gas mileage. Now however a dirty air filter will still cost you power, but it won’t really hurt your mileage. Why not? Because now days cars are so much smarter. They use electronic engine management systems connected to a host of sensors to meter the fuel, rather than a bunch of venturis, tubes, and holes in some brass. As the air filter gets dirtier and the airflow decreases, the electronics compensate by also decreasing the fuel flow so the air/fuel mixture is always correct. The problem is that you’ll lose plenty of power, so don’t let that filter get too dirty.

Here’s another one; leaving the tailgate down in a pickup will save gas. Actually according to recent tests it doesn’t. Remove the tailgate entirely and put a net across the opening.

Still more old timers myths that are supposed to increase your gas mileage, but in most cases, do little or actually have a detrimental effect on it include the “put it in neutral when going down hills” piece of advice. Although this actually works in older cars, it doesn’t in newer vehicles. That’s because in newer vehicles the electronic engine management systems actually shut off the fuel flow entirely when you are moving forward with the throttle plate in the closed position. That is only true when your rig is in gear. When you put it neutral the fuel cut off is not in effect, so you’re burning gas. Keep it in gear, just take your foot off the gas, and your cars ECU will stop feeding your engine for you.

These are just a few things that people just know are true about ways to get better gas mileage; except they really aren’t.

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.

As diesel fuel hovers between $4.50 and $4.95 a gallon, knowing how to improve diesel fuel economy is likely right at the top of your list, weather you drive a new Diesel Jetta TDI or a Chevy 2500 with a Duramax. If you are averaging over 40mpg in your new Jetta TDI, you may not have the same yearning for that knowledge as if you just finished pumping about $150 worth of Chevron’s finest into the saddle tanks of your 3/4 ton tow rig, but you get the point nonetheless.

With that in mind, here are some tricks you can use to get better fuel economy out of your diesel, weather you use it for towing, long freeway cruises, or just drive to work everyday like the rest of us poor slobs.

Diesel engines are internal combustion engines like gasoline engines but there are some important differences, the main one being they have no spark ignition system and burn a more oil-like fuel. The lack of an ignition system minimizes maintenance, such as the requirement to change spark plugs, spark plug wires, distributor cap and rotor, because there aren’t any! Most modern cars have eliminated all these parts except for the plugs themselves anyway by going to a coil-on-plug ignition system. If you’ve ever had to replace your coils on one of the new cars, you’ll probably long for the good old days of a traditional distributor that you could pick up at any auto parts store for $20.

Diesel engines use direct fuel injection systems. These inject the fuel directly (Hey, imagine that!) into the combustion chamber where it’s ignited by the heat produced by the diesel engine’s extremely high compression ratio. Some new gasoline engines, such as the new Cadillac 3.6 liter V-6, 2009 Porsche flat 6 engines, and the newer Audi engines are also using the direct fuel injection technique, combined with the gasoline engine’s spark ignition systems, to gain efficiency and maximize fuel economy.

So if you are driving an oil burner, how can you stretch every last mile out of a thankful?

For diesel powered vehicles many of the same fuel saving techniques apply as are used for gas powered vehicles; drive slower, clean out excess weight, don’t have a loaded roof rack if you don’t need to, keeping tires properly inflated, etc. There are some diesel specific fuel economy tricks, however that can be used to really make your gas powered brethren a bit jealous as you bypass the gas station.

How to Maximize Diesel Fuel Economy –

Learning how to correctly drive a diesel engine for the best fuel economy is very important, especially if you’ve spent your life behind the wheel of gas powered vehicles. Diesels just work a bit differently, and have about half the rpm range of a comparably sized gas engine. You’ll usually be turning much lower rpms on the freeway when driving a diesel powered vehicle, and that’s just the way these engines like it.

Use the cruise control –
One of the reasons that diesel engines are often chosen for duty in heavy commercial applications such as generators and pumps is that they like to be operated at a constant speed, and are most efficient when run that way. Remember that in your daily driving. Find the rpm that your engine is the most efficient for a given load and stay there. Use your trip computer to find the best instant mpg speed at the load ranges that you normally use and chart them. When traveling on the freeway set your cruise control for these speeds.

Short shift the engine –
Short shifting is a driving technique for manual transmission vehicles where the engine is shifted into the next gear well before its power peak and red line. For drivers that are accustomed to driving gas powered vehicles this may seem counter intuitive, but diesels typically don’t like to spend their time in the upper reaches of the tachometer. Shift at maximum torque point, which on diesel engines tend to be fairly low in the RPM range.

Choose a lower final drive –
If you’re buying a new pickup or SUV with a diesel engine option, you’ll often have a choice of different rear end (final drive) gear ratios when perusing the option sheet. Unless you’ll be spending most of your time towing very heavy loads (6,000+ lbs.), choose the lowest numerical ratio that’s available. If you’re searching for the best fuel economy, the lower (numerical) gear will really help you get it.

Don’t buy bargain basement diesel fuel –
Diesels are very sensitive to the quality of their fuel. One of the worst things you can do is feed them contaminated fuel, especially if it contains water. Steer clear of the low budget stations. The few cents a gallon you save could come back to bite you.

General Motors actually issued a technical service bulletin (TSB) relating to fuel economy in its diesel powered trucks. This would apply to most other brands of diesel trucks, in addition to SUVs and cars. Here are the factors listed in the GM TSB that can affect diesel powered fuel economy:
• Accessories that increase wind drag. Keep the bike rack, or ski carrier off your rig when you’re not heading out to the mountain. This is especially harmful to the mileage you’ll get in a diesel car with a smaller engine, as it causes it to work much harder than the same wind resistance increase on a big-engined diesel powered rig like a Duramax or Cummins pickup.
• Driving 65mph will lower fuel mileage up to 15% as compared to driving 55. This is especially true when towing a heavy load that has poor aerodynamics and a large frontal area, like your big wakeboarding boat with a tower.
• Frequent stops, changing speeds or otherwise poor driving habits. Diesels love steady state operating conditions and prove it by returning their best fuel economy when operated that way. Find the best fuel economy speed for a given load and just set the cruise control for that speed.
• Transmission problems such as OD automatics not shifting into OD, or the lockup torque convertor not locking up.
• Fuel system problems such as contaminated fuel filters. The fuel filter on a diesel is even more important than on a gasoline engined vehicle. Make sure the water separator is functioning properly.
• Final gear ratio. As noted above, when purchasing a new truck check the option box for the lowest numerical ratio possible unless you’ll be spending a significant portion of your time towing heavy loads, in which case you’ll want to go to a lower (higher numerical) gear ratio in the rear end.
• GVW (Gross Vehicle Weight).
• Wheel alignment and tire pressure – check your alignment and tire pressure. If either of these are out of adjustment or spec, it increases rolling resistance and reduces fuel economy.
• Misadjusted or dragging brakes – the same as above. In addition, make sure you don’t ride the brakes when driving. This behavior is fairly common, as evidenced by the dodos cruising down the freeway with their brake lights on.

Using diesel fuel additives –
Diesel engines burn a very different fuel than gas engines. One of the most important ratings that describes diesel is its’ cetane rating. Cetane is a measurement of its propensity to burn and support combustion; to a point, the higher the better.

Most commercially available diesel fuel runs around a 40 cetane rating. Not bad, except that most diesel engines found in pickups, such as the Duramax, Cummins, or Powerstroke like about 5 – 10 points higher than that. One way to raise the cetane rating of what you put in your tank is through the use of fuel additives. Diesel additives will also increase the lubricity of the fuel to help protect engine components and decrease internal friction. Both of these effects will increase your diesel’s fuel economy.

Take a look at the post I did last on the 3 best car modifications to increase gas mileage. The same 3 mods apply for diesel vehicles, and for many of the same reasons. In fact, one of them, reprogramming your diesel’s ECU, is one of the favored mods to radically increase your diesel’s power and torque too. The sophistication of the new controllers is pretty phenomenal. They can allow you to select different settings depending on your current use. If you’re towing for example, you can just dial up more grunt, but keep more conservative programming for daily driving to save fuel. They can even tell if your transmission is slipping and reduce the fuel to save your tranny.

This is a beginning primer on how to maximize fuel economy for your diesel powered car or truck. Since better fuel economy is one of the main reasons people buy diesel vehicles, there is a bit of gold in here.

Until next time.