Diesel engines have been around since the dawn of the automotive era. Over the years, diesels have become the engine of choice for powering heavy-duty trucks, buses, agricultural vehicles, off-road equipment, hard-working pickup trucks and stationary generators.

More recently, diesels are ­competing against hybrid and plug-in electric powertrains as an ­alternative to gasoline engines in passenger cars. The numbers are still relatively small in the U.S. with only about 800,000 passenger cars currently powered by a diesel ­engine.

But those numbers are ­expected to grow significantly in the years ahead – especially if fuel prices continue to rise and auto makers offer diesel-options in more makes and models.

By comparison, there are about 6 million diesel-powered light trucks registered in the U.S. and over 2 million diesel-powered heavy-duty trucks.

New clean diesel technology has drastically reduced emissions and now accounts for over 28% of all trucks registered in the U.S., according to R.L. Polk. Introduced in 2007 to comply with new government regulations, clean diesel engines are now found in nearly half a million heavy-duty trucks.

One of the changes that clean diesel technology brought with it was the need for higher-quality motor oils. The American Petroleum Institute (API) introduced the current CJ-4 oil standards back in 2006 so diesel motor oils would be compatible with 2007 model year engines equipped with exhaust gas recirculation (EGR), exhaust aftertreatment systems and designed to burn ultra-low sulfur (less than 15 ppm) diesel fuel. The higher operating temperatures and tougher emission requirements for clean diesel engines meant the oil had to provide better oxidation resistance, high temperature stability and soot control.

Diesel Oil Additives

One of the basic differences between oils formulated for diesel engines and those formulated for gasoline engines is more detergent and dispersant in the additive package.

Diesel engines (even clean diesels) still produce a lot of soot that ends up in the crankcase. If the oil can’t keep the soot in suspension, it can end up as sludge in the crankcase and elsewhere in the engine.

Diesel oils also contain a higher concentration of the anti-wear additive zinc-dialkyl-dithio-phosphate (ZDDP) to protect highly loaded sliding surfaces (like cam lobes and lifters) against wear.

The amount of ZDDP allowed in gasoline motor oils was cut back to 800 ppm in 2005 to help extend the life of the catalytic converter, but was allowed to remain at 1200 ppm in diesel motor oils.

The actual level of ZDDP in off-the-shelf diesel oils may vary from as low as 1000 ppm to as high as 1600 ppm according to various lab tests that have been performed by independent sources. That’s because the anti-wear properties of the oil depend, not only on the amount of ZDDP in the oil, but also other additives in the oil and the quality of the base oil itself.

The shift to low ZDDP gasoline motor oils in the market caused a sharp rise in flat tappet cam failures, especially in engines with stiffer than stock valve springs. Cam failure was not an issue in engines with roller cams because the rollers reduced friction on the cam lobes.

This lead many engine builders to recommend using diesel oil in gasoline engines if the engine had a flat tappet, high-lift performance cam and high-pressure valve springs.

The extra ZDDP in the diesel oil provided the extra protection needed to prevent the cam from failing. Today, we have numerous “racing oils” and “street performance oils” that are formulated with higher concentrations of ZDDP to protect flat tappet cams, as well as aftermarket ZDDP crankcase additives that can be used to fortify current gasoline oils in engines with flat tappet cams.

Diesel Oil Requirements

In addition to the API oil quality requirements, every OE engine supplier and vehicle manufacturer has its own oil specifications and viscosity recommendations. These include Allison, Caterpillar, Cummins, Detroit Diesel, Deutz, GM, Ford, Mack, Mercedes-Benz, Navistar, Volkswagen, Volvo and others. The specifications can vary depending on the model year and engine application. GM, for example, introduced its “dexos” specifications several years ago, and says that oils that meet its dexos2 specification should be used in its 2011 and newer diesel engines.

Oil Viscosity

For many years, 15W-40 had been the most common viscosity for diesel motor oils used in trucks. It provides a good high temperature protection and can be formulated from conventional base stocks or synthetics.

But, one of the drawbacks of a 15W-40 oil is that it makes the engine harder to crank when the engine is cold, so a thinner viscosity may be recommended for winter use in cold climates.

In recent years, a number of oil companies have introduced thinner 5W-40 diesel oils – not only for cold weather operation, but also for year-round use. Most of the 5W-40 diesel oils are a synthetic-blend or a full synthetic to achieve the cold flow characteristics needed for easy starting. Other cold weather diesel oils include 0W-30, which is formulated for subzero arctic-type conditions.

One of the benefits of using thinner oil is improved fuel economy. Thinner oils reduce drag and can help boost fuel economy from 1 to 3%. Switching a big over-the-road truck from a traditional 15W-40 oil to a full synthetic 5W-40 can produce significant fuel savings over time.

Of course, one of the tradeoffs of using a thinner full synthetic is its high initial cost, which can be up to two times or more than a conventional or blended motor oil.

Passenger car diesel applications are typically using thinner viscosity oils. The 2014 Chevy Cruze 2.0L turbo diesel is factory-filled with a dexos2 5W-30 motor oil. Many of the European turbo diesel powered cars also recommend 5W-30 as well as 5W-40 and 10W-40.

New Diesel Oil Standards & Viscosities

As of this writing, the target date for the introduction of a new set of API diesel oil standards is set for April 2016, almost 10 years after the last upgrade in oil standards. In the past, the main driving force in upgrading oil performance standards was emissions compliance. Today, the driving force is fuel economy and reducing carbon emissions.

API is still finalizing what exactly the new requirements and test procedures will be for what will likely be two new diesel oil ratings: one to replace the current CJ-4 standard (which will be backwards compatible for current CJ-4 applications), and a second oil standard (as yet unnamed) that will apply to 2016 and forward next generation diesel engines.

What they want is a new thinner viscosity oil that can provide better fuel economy while withstanding even higher operating temperatures with no sacrifice in durability, oxidation resistance, wear resistance and shear stability.

API is still developing the tests these new oils will have to pass in order to meet the new levels of performance. The current test procedure for determining oil viscosity is to heat an oil sample to 100 degrees C and measure how fast it flows through a calibrated orifice.

The test for the new 2016 diesel engine oil may involve heating the oil to 150 degrees C to measure its viscosity. Additional tests may include scuffing resistance, shear stability, oxidation stability and how well the oil can handle aeration.

There was also discussion as to whether or not a new test might be needed for compatibility with biodiesel fuels, but the consensus now is that biodiesel compatibility is not an issue now that biodiesel fuel quality has improved.

For now, the two new oil standards are code named PC11A for the oil that will replace the current CJ-4 oils, and PC11B for the next generation 2016 and forward engines. There may even be a new viscosity rating to help differentiate the PC11B oil from current viscosities that are on the market. According to one oil company, oils that meet the new PC11B requirements will likely have a high temperature viscosity rating around 26 (slightly lower than a traditional 30 weight), resulting in blends such as 5W-26 or 10W-26. The PC11B oils may be a blend of conventional and synthetic oil or full synthetic. It’s also likely that the new PC11B oil may NOT be backwards compatible with current or older diesel engines (that will be up to the diesel engine manufacturers to decide on a case by case basis). It may be okay to use PC11B oils in some 2007 and newer engines, or it may not. This may present some challenges for truck fleets that operate a mix of newer and older engines. Most fleets prefer to use a single grade and viscosity motor oil in all of its engines, but that may not be possible depending on what engine changes appear in 2016.

Future oil compatibility issues may seem to be far removed from engine builders who are overhauling older, high-mileage diesel engines. But as technology continues to evolve and move forward, we need to keep abreast of changes that eventually affect all aspects of engine building.

Diesel Break-In Oils

Engine break-in is a critical process that can make or break an engine. Using a high-quality engine assembly lube on all sliding surfaces as the engine goes together, and priming the oil system prior to the initial start-up are absolute musts for proper break-in protection. But what type of break-in oil should you use?

John Deere recommends using its special diesel break-in oil in John Deere engines. In fact, John Deere ships all of its new and remanufactured engines with break-in oil in the crankcase. John Deere’s “Plus-50 II” break-in oil (which is available in 15W-40 and 10W-30 viscosities) should only be used for the first 100 hours of engine operation. Once the engine is broken in, the oil should be drained and replaced with regular oil (conventional, synthetic blend or full synthetic).

Most other diesel engine manufacturers make no specific break-in oil recommendation, and say to use the same oil that would normally be used in the engine (usually a conventional 15W-40 oil). This oil can be used until the engine is fully broken in (which may not be until the first normally scheduled oil change interval or up to 10,000 miles), or it can be changed after a certain time or mileage period (which will vary depending on the application).

A number of oil suppliers have special break-in oils that can be used in gasoline or diesel engines. These products can be single weight or multi-viscosity and are usually formulated with a conventional mineral oil base stock and a special additive package that promotes rapid ring seating. Many break-in oils also contain higher levels of ZDDP for extra wear protection. Most break-in oils should only be used during the initial break-in process (1 to 2 hours), then drained and replaced with ordinary oil.

Oil Change Intervals

Vehicle manufacturers have been pushing extended service intervals to reduce maintenance costs for fleets and consumers. Fleets often base oil change intervals on the results of oil analysis, but most consumers either go by the OEM recommended service intervals or rely on an oil reminder service light to tell them when an oil change is needed.

On late model light trucks, 7,500 miles is the standard recommended oil change intervals for GM Duramax, Ford Powerstroke and Dodge Cummins turbo diesel engines. However, this is for “normal” (light duty) service. The recommended oil change interval for most “Severe Service” applications (vehicles that are used for towing, hauling heavy loads, operated off-road in dusty environments or spend a lot of time idling, especially during cold weather) is usually 3,000 miles. Most of these engines hold 10 to 12 quarts of oil, so changing the oil unnecessarily wastes money. Stretching the oil change intervals to reduce costs is fine provided a high-quality oil (such as a synthetic blend or full synthetic) is used along with OEM quality oil filtration.

With heavy-duty trucks, oil change intervals also depend on use. For light-duty over-the-road hauling, some OEMs say the oil can go 40,000 to 50,000 miles before a change is needed. As with the light pickup trucks, extended oil change intervals require a high-quality oil and good filtration. For harder use applications, the recommended service interval typically drops to 15,000 to 25,000 miles. Many of these engines hold up to 40 quarts or more of oil, so when the oil is changed it does have a significant impact on operating costs as well as engine durability and longevity.

Oil Filtration

Because diesel engines produce a lot of soot and combustion byproducts that end up in the crankcase, good filtration is needed to protect the engine from these contaminants. The oil filters on diesel engines are typically much larger and have a higher holding capacity than those on gasoline engines. Many heavy-duty trucks have used two separate oil filters: a full flow filter and a bypass filter to help assure good filtration under all operating conditions. Newer diesel oil filter designs often combine full flow and bypass features into a single filter. Combination filters typically have a wrap-around pleated full flow media inside with stacked disc bypass media at the top or bottom.

Full flow filters (or the full flow portion of a combination filter) typically trap debris 30 microns or larger, while bypass filters (or the bypass portion of a combination filter) capture contaminants down to 10 microns in size. Some combination filters can even trap particles as small as 5 microns. Smaller particles can actually cause more engine wear over time than larger particles.

Approximately 75% of the contaminants trapped by the oil filter are combustion byproducts (soot and sludge) rather than engine wear particles or dust or dirt from the outside environment.

The filter’s holding capacity (how much dirt it can hold) as well as its efficiency are important because both determine how long the filter can last before it has to be changed. You want a filter with high efficiency (98% or higher) to trap as many contaminants as possible, but you also want a filter that has adequate capacity so it doesn’t plug up before it is changed. If the filter media becomes clogged to the point where the filter goes into bypass mode, the engine will be running on unfiltered oil.

When an engine is being started for the first time, the oil filter should be prefilled with oil to minimize the time it takes the engine to develop normal oil pressure. The filter should also be changed every time the oil is changed, not every other time to reduce the risk of filter clogging.

Another tip that can prevent engine warranty claims or problems down the road is if the engine has an external oil cooler, the lines and/or cooler should be inspected and cleaned to make sure there are no contaminants lurking inside that could cause problems. Any junk in the oil cooler can pass right through to the engine’s main oil gallery that feeds the main bearings, cam bearings and timing gears.

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Ask any Mopar afficionado around the Midwest, “Who is the guy to go to if it has anything to do with a Hemi power plant?” And the answer which will probably be uttered is Tony DePillo and his Specialty Motorwerkes Company located in the Dayton, Ohio area. He does it all, from a speed shop owner, a parts fabricator, an engine tuner, a racer, and for purposes of this article, an engine builder.

He covers all applications with the legendary power plant including stock, street and strip. And, unlike many engine builders in motorsports, Tony has been a driver himself wheeling a vintage 1964 Plymouth Savoy Super Stock car which is painted in the motif of the famous “Honkin’ Hemi.” This guy’s veins definitely swirl with Mopar Blue.

“I’m a longtime Hemi fan which really made Chrysler in the 1950s, 1960s and now with the 5.7L and 6.1L Hemi’s. I grew up in northeast Ohio when Mopar national drag racers Arlan Vanke and Carlon Hine were burning up the strips with Hemi power. I was fortunate enough to be able to work with Vanke and it had a huge influence on me,” the Ohio State electrical engineering grad explained.

Tony laughed when he recalled his first Mopar machine, a ‘66 Satellite. “It was really beat up, but I drove it hard and beat it up even more. At the end, it was burning more oil than gas.”

Tony got involved in Super Stock drag racing in the early 1970s with a modified ‘68 Dodge Coronet R/T and a ‘68 Dodge Charger 440 Six-Pack. Besides driving, Tony was also heavily involved in the tuning activities.

However, his involvement there would end after the 1985 NHRA Nationals, when Tony felt that the Mopar engines were not getting a fair break in the engine rules.

In 1998, the National Street Car Association (NSCA) was formed, with Tony being an active member as well as the group’s president during it’s decade-long run. The NSCA, a sanctioning body for heads-up, street legal racing that focused a lot on nostalgia vehicles, ended in 2007. However, even today, Tony can still be found behind the wheel of his nostalgic Honkin’ Hemi.

Setting Up Shop

During the years prior to forming the NSCA, Tony built up his Mopar reputation with the start of his business, Specialty Motorwerkes, in 1986 (specialtymotorwerkes.com).

The shop continues to build engines today. Besides the American muscle, his company also does work on many high-brow import machines.

But these days, you will find the boss in an area at the back of the shop that deals with engines that have spark plugs coming through the valve covers.

Tony will tell you that the Hemi building activities are based on the customer’s desires but that he will make suggestions if he feels the

build-up is unrealistic. Tony explained, “There are a lot of guys looking for more power under the hood, but with retaining the stock look of the engine. Of course, the vintage Mopar muscle cars are a good recipient of that type of

treatment. The type of work we would do there would be improved pistons and rods which help in increasing the compression ratios.

“The oiling system is often the weak link in this build-up and we might use a higher capacity oil pan and a higher volume oil pump. With the Nostalgic Super Stock cars, just about anything goes.” And would you believe that there are sometimes as much as three years between Super Stock engine servicing. Tony added that on occasion, he will build a complete turn-key nostalgic drag car for the customer. Earlier he did such a job, twice, with the building of a pair of clone A990 Mopar drag cars each carrying 478cid Hemis.

At the present time, there is a main emphasis on the building of Nostalgic Super Stock engines, but he’s not adverse to working on the upgrade of a pure street legal Mopar, or one that can be adaptable for either street or strip. With those types of upgrades, Tony likes to maintain the external factory look of the engine.

On occasion, there is also some dabbling with the early generation Hemi’s.

“I have done engines with 354 Hemi heads for street rods. And also, there have also been several 392 Hemis that I

have modified.”

To generate maximum power with his top-gun engines, Tony has collaborated on a number of custom pieces to become a part of his performance package.

“One such piece is my custom oil pan which is not nearly as tall, or volume-wise as large, as the present oil pans. It also enables me to mount the engine lower which drops the center of gravity of the car,” he said. There are also DePillo-designed intake manifolds, which are fabricated by Hogan. In addition, CP Pistons has worked with Tony in creating Hemi-only billet pistons, which are legal for NHRA Super Stock cars. They are very light at only 570 grams each. Finally, he’s also worked with Glenn Stires in the design and development of lifters and cams.

In more recent years, Tony has been involved with the new 5.7L and 6.1L Hemi engines. “I think these engines are excellent,

actually fixing some of the problems of the original. The engines have stronger pushrods and rocker arms. They are very durable and are easily capable of running 250,000 miles. They still have some of the old-school characteristics.

“Upgrading these engines is pretty straight-forward with mostly just add-on pieces. But it is very compatible to the Pro-Charger blower and will kick up the power by 150-175 horses,” he indicated.

With such awesome demonstrated capabilities, it seems like a logical question to ask of this big-time Hemi builder,

what is the simplest way to pump up a Hemi. Tony quickly responded,

“Hey, that’s an easy question for me. What I do is increase both the compression ratio and the air flow. You know, this engine is nothing more than a big air pump and I want to give it all the air flow it can handle.”

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AMSOIL Diesel Injector Cleaner targets tough deposits on high-pressure common-rail injectors. It is formulated for all diesel fuel systems, provides maximum horsepower, and reduces smoke and emissions. While increasing fuel economy up to 4.5%, AMSOIL Diesel Injector Clean also adds lubricity to reduce fuel-pump and injector wear. www.amsoil.com

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Diamond Racing Pistons has announced new, sturdy 2618 billet aluminum pistons that replace the original equipment aluminum castings for Ford Power Stroke V8 6.0 and 7.3L turbocharged diesel engines. The pistons receive the protection of a Double Diamond coat that adds longevity, reduces friction and decreases wear. Shelf-stock part numbers are available in all common bore sizes, while custom units are offered in virtually any bore size.

Standard dish volumes and swirl chambers with undercut rims to promote turbulence are used for shelf-stock part numbers. Conveniently, custom dish designs are produced to customers’ specifications. Further customized options are engineered for competition applications, including side gas-ports to enhance ring seal.

To complete the kit, Diamond provides a three-ring pack using a steel top ring, an RBT second ring and a conventional oil control ring. Their thicknesses measure 1/16, 1/16, and 3/16in. www.DiamondRacing.net

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If you think the torque of that monster diesel is something to brag about, then you should feel it with the extra power of NOS from Holley. This kit p/n 02519NOS, fits all diesel applications and works well with stock and modified applications. Vehicles with computer upgrades will benefit even more as nitrous will aid in a clean combustion. Comes complete with 10 lb. bottle, bottle brackets, nitrous feed line, large nitrous solenoid, electrical wiring and complete instructions. Features adjustable HP settings, gains up to 75 hp on stock applications and higher hp gains with computer modifications. www.holley.com

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