Essential Tips for Optimizing Cummins 6.7L Diesel Performance

If you own a Ram truck with the Cummins 6.7L turbo diesel and enjoy watching videos on YouTube, chances are that you’ve come across a video by YouTube creator Marion Blair. Marion has been around diesels his entire life. He studied mechanical engineering, holds a commercial pilot’s license, and served in the Marine Corps from 1968 to 1970, where he worked as a motor pool mechanic and wrecker driver. He also worked with Exxon Mobil in mechanical, electrical, and supervisory assignments until 2004, then later with Chevron until retiring in 2014. Marion has owned two trucks with Cummins diesels. His current rig is a 2014 Ram 2500 with a Cummins 6.7L Turbo Diesel. A prolific and passionate YouTube content creator, Marion has produced countless videos over the years. In this article, Marion Blair provides valuable tips on optimizing the performance of the Cummins 6.7L turbo diesel.

Hi Marion. Thanks for taking the time to talk with us. Can you tell us a little bit about yourself?

Marion Blair: Thank you. My interest in diesels began at an early age. I was born and raised next to a power plant where my Father worked in New Iberia, Louisiana. The relatively small power plant has four very large Cooper-Bessemer and Clark diesel engines producing electricity. I grew up to the drone of these low speed industrial engines. My Dad taught me all about them and I knew who Rudolf Diesel was before I knew who our president was. Although I received mechanical and electrical training throughout my career, my father was the core of my education. He spent many hours with me laying on a piece of cardboard in our gravel driveway teaching me how to do things on my 1953 Chevy. He was a great mechanic, patient and detailed, close enough wasn’t good enough.

I studied Mechanical Engineering, obtained my commercial pilot’s license, and served two years in the US Marine Corps from 1968 to 1970. I was assigned to the infantry and later in the Camp Pendleton motor pool as a mechanic and wrecker driver. I’ve been married for 51 years, spent 33 years with Exxon Mobil in mechanical, electrical and supervisory assignments till retirement as a senior drilling supervisor. Following retirement from Exxon, I spent 10 years with Chevron’s Asset Development group retiring in 2014. My hobbies are RV travel, Camping, Boating, Fishing, motorcycles and flying my 1956 Cessna 172.

In 1965 I rode a Honda 305 Super Hawk to Pikes Peak, California and back to Louisiana and repeated this trip 47 years later on a Honda Goldwing. If you are interested in motorcycles you can see a video of the last bike I restored.

What type of recreational vehicles have you owned over the years?

Marion Blair: I’ve had five RV’s from various manufacturers. All conventional travel trailers. I think my favorite was a 27-foot Mobile Scout. In that price range, I didn’t find a lot of difference in the various brands as they are all similar construction and components. The Mobile Scout’s floor plan however was ideal for my wife and I and it had a one-piece aluminum roof which was nice. It was hell on black streaks for some reason. I hadn’t had that problem with rubber roofs. That was in the mid 90’s. I mounted an electric start Honda 3.8K generator on the tongue for boondocking.

All my campers have been anywhere from 18-feet to 27-feet. I’m pretty much of a minimalist, I guess. My current camper is a 21-foot Rockwood with a single slide-out. I don’t really like slide-outs since it’s another point to leak or something else to brake and ruin a vacation. But they are nice once set up. I really like the mobility of the truck campers.

How long have you owned trucks with Cummins diesel engines?

Marion Blair: Since 1995 for Cummins. I try to keep a vehicle for at least 10 years and have mostly done that other than a period when I was working overseas. My first diesel was the infamous Olds 88 with the 5.7 L V-8 diesel engine. It was a disaster for me and probably everyone that owned one. It wasn’t until GM teamed up with Isuzu, that they finally started producing a decent engine for the Duramax. Ford had its issues also, especially with the Navistar 6.0L Power Stroke turbo diesel. However, I think the Current crop of Rams, GMs and Fords are all good engines.

What truck do you currently own and how long have you owned it?

Marion Blair: Although I looked at Ford and Chevy with an open mind, I felt the Cummins-powered Ram was still my choice. I currently own a 2014 2500 4×4 Ram Laramie, which I purchased new in April 2014. My use pattern has been 60 percent towing, 40 percent highway and grocery getting. It’s 100 percent stock.

The 2013 through 2018 are all very similar, so I’ve had no incentive to upgrade. The fifth generation engines have some interesting changes. Cummins increased the torque and horsepower and have a bigger turbo and beefed up the 68RFE transmission. It’s getting tempting and I’m getting close to my 10 years milestone with the Laramie. But, I really like this truck and plan on keeping it.

So do we. What drew you to the Ram 2500? Was it the reliable Cummins 6.7L engine or something else?

Marion Blair: My previous experience with Cummins. I really liked the updated Ram body design and they added some nice features. Simple but useful things like extending the running board just past the passenger door so you had a step up to get stuff out of the bed, the storage under the floor of the rear floor board and the excellent driver display and a usable GPS in the 8.4AN radio. Little simple things, but so usable. The rear progressive coil springs really improved the ride without sacrificing the load capacity.

I also liked that the fourth generation Ram didn’t require EGR service since DEF injection was added. A lot of folks didn’t like this, but it reduced NOX and therefore required less EGR and no service to the EGR valve.  Cummins also stretched the oil change interval to 15,000 miles or 6 months as a result.

What have you learned about the Cummins 6.7L that you didn’t know before?

Marion Blair: The diesel engine itself is simple. Add the DPF, DEF, EGR, DOX and Catalytic converter and troubleshooting these trucks can be humbling. Learning the 6.7L EPA-compliant diesel engine was challenging and Ram’s service manual is lacking to say the least. Engines are computer controlled with inputs from sensors throughout the intake and exhaust system.

I’m constantly learning and sharing on my YouTube channel. As the EPA put more limits on exhaust emissions it’s forced us to dig deeper into how these nearly all electronically controlled systems work. I do a lot of web research, phone calling and emailing. The Internet is an excellent source.

What has been your most popular video?

Ironically, my most popular video to date is still the, “going through the $15 car wash.” That’s a fluke, I don’t understand it. It wasn’t planned at all. I happened to turn on my GoPro and recorded it. It has over 489,000 views to date.

My most popular videos are always Ram operating or maintenance related videos. I record the PCM data (100 parameters) 100 percent of the time. Like an airline’s black box, having access to this data takes the mystery out of what the engine and components are doing. The data is easily exported to an Excel file. For example, a popular post on Cummins forums has been, “what is the purpose of the foam covered baffle in the air intake?” Some removed the baffle and claimed more power? I answered that question definitively with data. This video is a perfect example of the things I do in my videos. In the video I made four full throttle runs with and without the baffle and it definitively answered the question. The take away from this is; before you make any chances to your truck, consider the possibility of unintended consequences.

Another question was whether or not the front drive shaft (4×4) was turning at highway speeds and if it wasn’t, why the need to grease it every 7,500 miles. I strapped a GoPro under my truck looking at the drive shaft while running 60 mph. It doesn’t move.

It’s nice to get a “thank you” from someone who is in a jam somewhere and looked up one of my videos that helped them. In fact, I just read a recent comment from a viewer that accidentally pumped gasoline in his diesel tank. It happens.

“How to start a Ram with a dead Key Fob,” generates many comments from people who faced this dilemma in a parking lot somewhere and got on YouTube to search for an answer.

What made you want to start a YouTube channel?

Marion Blair: It was accidental. One of my hobbies has always been photography. In every house I’ve lived in, one of the bathrooms was a converted darkroom. When digital photography became mainstream, I sold all my negative film cameras and went all-in on digital photography. I really never had much interest in video photography until digital camera became popular. I’ve owned a few camcorders over the years but the recording quality wasn’t very good and it was a hassle to pull out the projector and screen. When the digital camera first came about, that all changed and I slowly began to make short videos. I started videoing a few things on my truck and posting on YouTube. I realized there were a lot of people interested and was slowly building subscribers. You can find my channel here.

What things do you recommend that Cummins 6.7L owners do to ensure that their trucks run well?

Marion Blair: I do a lot of videos on this question. If you are inclined, you can save a lot of money doing your own maintenance. It’s an easy truck to work on. These trucks require very little maintenance. Change your oil every six months regardless of mileage. Oil gets dirty and contaminated whether it’s synthetic or mineral. Change all fluids as per the owner’s manual and use fluids approved only by Mopar. Changing fuel filters and air filter as recommended.

Fueling at high volume stations will usually have less chance of picking up bad fuel. If you get a water in fuel light, shut down immediately and drain the filter. If it’s a significant amount, drain the entire tank. I have a video on how to do this from the fuse box while on the road if necessary. Water is a diesel killer.

Proper operation is as important for engine and transmission longevity as maintenance. When towing, take the transmission out of drive and select a gear that prevents the transmission from shifting down on overpasses and small inclines. Your transmission will thank you and you won’t have transmission problems. And of course, use tow mode when towing. I use the exhaust brake whether towing or not. It saves on brake wear.

I have numerous videos on the most significant things to check on the Ram. This one kind of consolidates the most significant things to check. Don’t abuse your truck—800 foot-pounds will tear up anything eventually.

We love the exhaust brake feature. What do you like about the Cummins 6.7L engine?

Marion Blair:  You know the old saying, “don’t worry about the mule, just load the wagon.” The mule is the Cummins. The Cummins B6.7L is the industrial version of the engine in our truck. It’s the same engine with Ram’s SCR to meet EPA emissions requirements. It’s an old proven design. The I-6 design develops it’s torque and horsepower at a lower rpms than a comparable displacement V-8’s. The lower rpm and natural balance of the I-6 makes for a quieter ride with less vibration. Fewer pistons, valves etc. makes for a more fuel efficient engine than a V-8.

Ram (Dodge) has a long relationship with Cummins. Over the years they’ve improved the chassis and suspension. It’s been a work in progress to get the Ram chassis to where it is today. They are not perfect but continuously improving the ride.

The Holset VGT turbocharger is a simple one-piece sliding nozzle as opposed to its competitors with individual vanes which are more prone to sticking and wear. On my original 1995 Cummins 5.9L (manual transmission) the only thing electrical on it was the fuel pump solenoid. I did a lot of valve adjustments, however, as it was required every 24,000 miles. My current 2014 requires it every 150,000 miles. Cummins has always had a solid lifter, however, the fifth generations are now hydraulic. Improved oils and metallurgy, have made lifter failure and sticking near nonexistent.

Is there anything that has disappointed you about the Cummins 6.7L engine?

Marion Blair: The grid heater is a possible failure point, which can cause catastrophic engine failure. But there’s a simple test affectionately called the giggle test. On some trucks, it’s either loose from original assembly or it loosens gradually from use. When that happens, the nut which is in the intake manifold begins to arc to ground falling off and entering a cylinder. I have a video on how to perform the giggle test. I’ve had several comments from people who checked this and found the problem before it caused damage. It’s apparently very rare, but happens and Ram/Cummins needs to address this. Another solution is to disconnect the grid heater at the passenger side battery.

A few minor things could have better access for easier maintenance. Like the grease fitting on the Cardan joint on the 4WD shaft.  It’s the only grease fitting on the entire truck.

Is there anything that has disappointed you about your Ram 2500?

Marion Blair: The CD service manual is full of clone errors and contradictions. The information is very vague and lacking detail. And to boot, it doesn’t have a search feature. It’s terrible. The recall fix on the front drag link recall (V06) is another sore point. Welding the lock nuts creates a nightmare for future steering alignment. I haven’t performed that recall yet. Lock wiring the nuts would have been a better answer.

The oil filter accessibility is not good for 4WD trucks. You either have to go through the fender or take the intake apart. I go through the fender as I don’t like taking the intake apart. This video sums up my evolution of making oil changes easier.

Up until the fifth generation, the fourth generation trucks had no option for rear axle ratio. The new trucks give you more options. I prefer the 3.73 ratio although the Ram does fine in fifth gear, sixth gear is too tall for most towing. The 6.7L towing rpm is optimum between 1,600 and 1,800 rpms. The mpg empty is excellent. I average 22-24 mpg at interstate speeds.

Towing mileage is dependent on aerodynamics. Cummins has some excellent research material on fuel economy. They compiled what they call the “rock-solid fuel economy rules” for heavy duty trucks, but is applicable to our trucks also. For example, here is one of Cummins rock solid rules: “every 2 percent reduction in aerodynamic drag results in approximately 1 percent improvement in fuel economy. Above 55 mph, each 1 mph increase in vehicle speed decreases fuel economy by 0.1 mpg.” I really like this stuff. There are many more and worth reading. You can see them all in this pdf link.

That canoe actually increases my mileage a mile or two. I’ve got data on it and will eventually put the results in a video. The perfect solution for this setup would be a topper slopping up toward the back as a wind deflector.  I’ve tried a wind deflector, but it actually reduced my mileage.

What has been the most gratifying feedback that you’ve got from your YouTube subscribers?

Marion Blair: As mentioned, comments like, “you saved me.” I get some really good feedback from people thanking me for helping them perform maintenance and especially when a video has helped someone get out of trouble. It’s why I continue the channel. I read every comment. If it’s in another language, I use Google translate to read and reply.

Additionally, the heart-felt comments I’ve received offering prayers for my wife’s health struggles. There are some really caring, kind people in this world. I don’t talk about my personal life in my videos, but things slip out. My wife has had a 25-year struggle with various forms of cancer and recently fought her way from a 20 percent chance of survival through a stem cell transplant to a now 65 percent chance of a total cure. She is currently recovering slowly and we are back home in Lafayette after living in my camper and an apartment since February.

Is there anything else you’d like to tell us before we close?

Marion Blair: Thank you for this opportunity, Mike. I hope it’s not like some of my rambling videos, haha.  The truck and camping folks are the best. We help each other. We know each other even when we’ve never met.  These campers and truck enthusiast are all good people and I’m proud to be a part of them. Enjoy your truck.  Take care of it but use it, enjoy it. And thanks to all the people who watch my videos.

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About Mello Mike 706 Articles
Mello Mike is an Arizona native, author, and the founder of Truck Camper Adventure. He's been RV'ing since 2002, is a certified RVIA Level 1 RV Technician, and has restored several Airstream travel trailers. A communications expert and licensed ham radio operator, he retired from the U.S. Navy in 2004 as a CWO3 after 24 years, worked in project management, and now runs Truck Camper Adventure full-time. He also does some RV consulting, repairs, and inspections on the side. He currently rolls in a 4WD Ram 3500 outfitted with a SherpTek truck bed with a Bundutec Roadrunner mounted on top. - KK7TCA

1 Comment

  1. A great article for a newby diesel owner like me. I’m a year into my Cummins 6.7 L and it is sometimes a bit intimidating so it is reassuring to hear Marion’s comments. Diesel prices have been hurting but I get relatively good mileage with my Alaskan camper on back. I’ll be going through the videos and am happy to find Marion likes the Peak Platinum DEF which I have been using so far. Thanks to you both.

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