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10 Ways You’re Killing Your Diesel

Easily Avoided Common Mistakes

Text By Jason Thompson, Photography by

Since the cost of replacing the diesel engine in your pickup is about the same as buying a new car from the dealership—it’s important to keep it alive as long as possible. Although almost everyone thinks of themselves as diesel experts, bad maintenance and usage practices abound. We know this because these easy-to-fix mistakes are keeping diesel shops very busy across the country. We’ve made a list of the top 10 deadly sins, which are damning far too many diesels to an early demise.

1. You’re Not Changing Your Fuel Filter
A clogged fuel filter can damage expensive injection pumps and injectors. Diesel fuel injection systems create a great deal of heat, and they rely on unobstructed fuel flow to keep the pump and injectors cool. As the fuel filter plugs up, the flow of fuel is restricted. In extreme cases, this extra pressure can cause a filter failure, which sends contamination directly into the injection system.

2. You’re Not Changing Your Air Filter
When the air filter gets clogged, fuel economy begins to suffer. A clogged air filter also causes the turbo to spin faster as it attempts to supply the engine with air. If dirt gets past the air filter because it was not installed properly or there is a leak in a boot—severe turbo, valve, and piston engine damage can occur in minutes. Driving down a gravel road may be all it takes to scour the cylinder walls.

Changing your in-cab air filter on a regular basis will make your fan motor live longer and keep your hard-to-clean air ducts less dusty. This will make you want to keep your truck alive longer.

3. You’re Not Changing Your Oil
Oil filters are important because they remove contaminants found in the oil. Oil analysis laboratories examine samples of oil from diesel engines and can determine a motor’s health without performing major surgery. The tests include a spectral exam that establishes the amount of wear metals in the oil, which indicates the level of bearing failure or other mechanical problems. Silica (dirt) is by far the biggest factor in engine wear and intrudes past seals and filters. As it combines with carbon, silica forms an abrasive called carborundum, which is similar in hardness to diamonds.

Silicone is an oil additive and anti-foaming agent also measured by the labs. From this information, you’ll be able to see how far you can extend your oil change. Coolant in the oil can indicate a major engine problem—some say glycol is the number one engine killer. The flashpoint of the oil is also typically tested. This information will tell you if you have fuel in the oil, which also accelerates engine failure.

4. You’re Forgetting to Mind Your Fluids
It’s important to change your engine oil, coolant, transmission fluid, and power steering fluid. One look inside the valvebody of a modern automatic transmission reveals the precision internals that need clean fluid in order to operate properly. Not adding a bypass engine and transmission oil filter to your engine isn’t murder, but it could be considered neglect. These devices work by screening the fluid down to 3 microns or less—that fine filtering would clog a full-flow filter. They can do this by only taking a small amount of oil at a time—so as not to affect normal flow. Installing a coolant filter is like giving your truck a liver or a kidney. Although the initial expense hurts—your truck will pay you back. Bad coolant will clog passages, which will cause overheated parts.

5. You’re not Letting Your Engine Warm Up
Don’t be that guy who starts his cold engine and immediately revs it up. The only thing you’re showing off is that you don’t know your turbo and engine bearings won’t get lubricated properly with cold, thick oil. Let your engine warm up like you warm up in the morning. Let the glow plugs and intake heater do their job. Fire the engine and give it some time for the combustion heat to warm the engine evenly.

This practice is very important on extremely cold mornings. Hot and cold engine parts expand at different rates, so gaps can form, which could cause leaks or gasket failures. Wait until your engine oil and coolant temperature gauges show you are in the right operating range. You do have these readings…don’t you? Also, if it’s really cold, don’t turn the steering wheel too much right away or you could risk blowing a hydraulic hose. The other thing that’ll keep your engine running longer is preheated coolant. The more cold-starts your diesel is subjected to, the shorter its lifespan will be. Inconsistent metal expansion and poor-flowing (thick) lubricants don’t provide protection from moving parts.

Another thing to worry about is fuel washing the cylinder walls before compression ignition can occur. Here is a message we got from a reader from the North Pole: “I have both batteries heated, the block heated, and two heating pads on the oil pan. The transmission is not heated, because it’s a stick. The intercooler is totally blocked as well. I might just put a pad on the transfer case and front differential, but it warms after about a mile of driving in four-wheel drive.” Diesel-fueled auxiliary heaters are also an option. It’s also just as important to let your diesel cool off before you shut it down. A turbo timer will do this automatically for you, because if it gets shut off too soon, oil will overheat, break down, and destroy turbo bearings.

6. You’re Not Reading the Smoke Signals
Don’t assume you can get by with worn-out injectors. If your truck is smoking black more than usual, that’s a possible sign your injectors need replacing. Another sign they are bad is if they start making noises. A diagnostic tool is able to individually shut down each injector to see which one is the culprit. White smoke often indicates coolant in the combustion chamber—either a sign of a head gasket failure or EGR cooler failure (if equipped). Blue smoke usually indicates engine oil in the combustion chamber—either from leaking piston rings or a bad valve seal. Insufficient compression can also cause a smoky engine.

7. You’re Not Keeping Your Truck Clean
Even if your truck is in perfect mechanical shape, it can still fall apart underneath you because rust never sleeps. Those who live in the Southwest don’t really have to worry about rust because it is too dry for the chemical reaction to take place. Everybody else should make it a point to keep paint chips filled with touchup paint and have a fresh coat of wax applied at least three times a year. During the winter months, when chemicals are applied to the roads to melt ice, you can’t wash your truck enough. During the rest of the year, avoid splashing through puddles, make sure your mudflaps are functioning, and try to avoid gravel roads if possible.

8. You’re Overheating Your Engine
We’ve watched the vicious cycle of modify, race, and then destroy one’s engine play out more times than we’d like to see, but some people still don’t believe certain truths until they learn them the hard way. When making any modification to your diesel, it’s absolutely necessary to keep track of all the engine temperatures. Even stock vehicles can use the extra insurance that comes with knowledge of the coolant, exhaust gas temperature (EGT), and engine oil temperature. You can also use this information to diagnose oil coolers or cooling system failures.

9. Centrifugal Force Is Wearing Your Truck Out
For those on a tight budget, the unforeseen cost of a new set of tires (because the old ones prematurely wore out) can be a truck’s death sentence. Poor alignment, along with under-inflated tires, can cause bad fuel mileage and tires with uneven wear patterns. A bent rim or severely unbalanced tire can cause axle-bearing failure. An out-of-balance driveshaft can cause axle pinion bearing wear and transmission or transfer case damage. It’s also important to keep the U-joints greased or replaced. Driveline maintenance also includes changing your differential fluid.

10. You’re Poisoning Your Fuel Tank
According to the marine diesel industry, most engine problems begin in the fuel tank. This is because water intrusion is more present on the seas than it is on land. Still, according to BP, “Under normal storage conditions, diesel fuel can be expected to stay in a usable condition for 12 months or longer at an ambient of 68 degrees Fahrenheit.” Yet the lifespan of diesel drops to, “6 to 12 months at an ambient temperature higher than 86 degrees Fahrenheit.” As diesel fuel ages, BP points out that, “fine sediment and gum forms in the diesel brought about by the reaction of diesel components with oxygen from the air. The fine sediment and gum will block fuel filters, leading to fuel starvation and the engine stopping. Frequent filter changes are then required to keep the engine going. The gums and sediments do not burn in the engine very well and can lead to carbon and soot deposits on injectors and other combustion surfaces.”

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By Jason Thompson
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44 comments
George A Frost
George A Frost

Logan lake don't know crap I've had several power strokes and know several people that have had them I can show atleast 10 that have over 300,000 and never been inside motor for anything and have had the piss run out of you will never get a dodge body to hold up that long without falling apart

Billy Geduhn
Billy Geduhn

I have 2001 Ford F-350 7.3 360,000 mi you keep up with them, they'll run Forever

Logan Lake
Logan Lake

That's a pretty good maintenance regiment Karl Barnesjr, the key is consistency. Another good tool everyone can use is sending off your own oil samples to get them analyzed. You can Google oil samples and find a company that will do it. I know amsoil offers this service , for oil sampling. Just check and see the costs differences in other companies as well if you prefer.

Karl Barnesjr
Karl Barnesjr

Logan Lake, I still use regular oil, 2009 6.4 p.s.d. stock, oil and both fuel filters changes every 200 hrs, no more than 5000 miles, coolant changes @ 45 thousand miles, differential fluid front/rear, transmission fluid and filter every 30 thousand, is that ok until I decide to delete?

Corey Lake
Corey Lake

ford cemetery... seems pretty sad all those fords died

Darrell Childress
Darrell Childress

I went from 5.9 to 6.7 Cummins, I like the power of the 6.7 and the 6spd automatic; but miss the economy of the 5.9. No DPF on my truck or catalytic converter. Bully dog upgrade and K&N filter help a lot, more to go or may just sell and go back to 5.9. Had a Ford 7.3 and that was the best powerstroke they produced by far.

Logan Lake
Logan Lake

Yep every make and model has it's issues. Just depends on how much you want to invest to fix them, that's a big problem now days, instead of fixing one issue that yes may cost a lot. People go out trade in for newer vehicle. Depending on the circumstances you were better off fixing the older one.. to each there own.

Andrew Hershfeld
Andrew Hershfeld

Dominic you're an idiot, 6.0's may have problems, but what engine doesn't. The fixes for the 6.0L isn't that hard to do. Plus if you take care of them they will last a long time. Not uncommon to see them with 200k miles or more.

Logan Lake
Logan Lake

I personally stay away from all powerstrokes , I like working on trucks just not constantly lol. Although the 6.7 is better then there 6.0 problem child. A lot of our ambulances have 6.0 and 6.7, most are now internationals in a ford chassis. I will be nice and just say stay away from them.

Casey Nepa
Casey Nepa

too much sex in the cab and talking on the cell phone

Darren Fike
Darren Fike

logan lake, what about ford 6.7 powerstroke? any opinions? pro and con?

Logan Lake
Logan Lake

I personally don't like the new 6.7 dodges, or Ford's 6.0 , I love my 5.9 Cummins , I've always been a Chevy guy , but love Cummins. Dodge has a lot of steering issues which I've fixed in my truck. And Ford's 6.0 is a basket case. Every make has it's positive and negative sides. Not here to bash makes. Everyone has there preferences, I've owned Chevy, gmc, Ford's, and dodge. I absolutely love the Cummins engine. I've built mine into my own personal crew cab corvette lol. 20k in performance upgrades lol I love my horsepower and torque, I can race , tow, or go off roading, or whatever I want to do.

Darren Fike
Darren Fike

ok as for alaska and idaho for winter period..which oil weight is best use for? reg oil weight and synthetic oil weight?

Ian Walker
Ian Walker

My top tip is to make sure you dont just do short trips or round town low speeds all the time, it needs a highway run from time to time.

Logan Lake
Logan Lake

A lot depends on weather. How hot and cold it is were you live. I work on detriots, Cummins, international, and powerstrokes. Military applications and fire trucks etc. In Arizona. We use 15w40 in most all those applications delco or 76 brand. And 40 weight in the much older detriots. Chevrons full synthetics are good, each oil has a viscosity and weather rating. I'm sure your owners manual will say 15w-40 or 5w-40. The newer diesels with all the new emissions crap on them strictly state to use what the dealer recomends. If your breaking in a new engine of course don't use synthetics right off the bat it won't allow the components to seat properly , you can go from regular oil to a synthetic blend, to full synthetic. If you like a certain product, chevron, mobile on, amsoil etc. I say stick to one , changing your oil with different blends constantly can possibly cause faster engine wear etc. There are a lot of factors in all of this of course. Ensure whatever you use is rated by the region you live, your not going to use a thinner oil in Alaska vs Arizona. You'll damage your engine. Owners manuals will say what oils they recommend by temperatures. I could talk all day about ratings and uses of oils lol

Darren Fike
Darren Fike

logan, i have good questions for you.... do you think a synthetic oil like shell 10W-30(for diesel) is good for ford's 6.7 powerstroke? what about chevron's delo 400 15W-40 for 6.7 powerstroke?? how good is chevron's full synetic diesel oil 5W-40 for 6.7 ford? what is best oil other than amsoil? i am doing researching to gather some opinions from people before i consider to buy a ford f250 powerstroke...how good is dodge's 6.7?

Logan Lake
Logan Lake

No I'm not an amsoil dealer, I just trust the data behind there product. I also use royal purple, mobile one etc. There are a lot of good synthetic oils out there. Just depends on what your individual preferences are.

Logan Lake
Logan Lake

You should inspect your air filter every 3,000 miles when you get your oil changed. Diesel owners check at 3,000 also although most diesel owners change there oil only every year. Or 6-9 thousand miles depending on if you tow a lot etc. They make 25,000 mile oil filters and oils you can run longer in diesels. Again it all depends on how you use your truck, towing etc. Always refer to your owners manual and ask a tech. Feel free to pm me. I'll answer anything you have.

Fred Bear
Fred Bear

North Dakota junkyards. 6.0's as far as the eye can see.. Kinda sad really.

Mitch Dukes
Mitch Dukes

Your post will not load to my fb not sure why

David Wysocky
David Wysocky

I can't trust anyone's opinion that uses amsoil and makes it a point to say so. "Dealer" by chance? Seriously though, Logan, all good advice other than amsoil.

Scott Powers
Scott Powers

^ good question. I normally shut down if I'm going to be sitting for a couple of minutes, unless the truck is stone cold. Idling isn't the best for any engine and you're getting 0 mpg so that's my take on it. It's crazy how long it takes the oil to warm up when it's cold out so I hate short trips too. I take the gas dodge when it's going to be a short trip. I don't let my trucks warm up too much in the morning,

Logan Lake
Logan Lake

It's called proper preventative maintenance. Teach your girlfriends and wife's what the wait to start light means and does. I'm a diesel technician US army and civilian. I personally use a turbo timer to turn off my truck at a set EGT temp. Turning off a hot diesel at high EGT's can kill your turbo, I use Amsoil full synthetic oils. I have external fuel filtration etc. I love my 5.9 Cummins and it loves me. Changing your fluids , checking simple things like tire pressures fluids etc, can save you a multitude of headaches. And money. Read your owners manual on schedule maintenance by mileage and or by fluid ages. Do this and any car you own will last.

Jeffrey Kumjian
Jeffrey Kumjian

When should you change your Air filter (how many miles)?

Raymond Casanova
Raymond Casanova

Question: If your just running into the house/shop for _______ minutes, it's better to leave it running. I've heard 10, & I've heard idling is the worst on an engine (not including warm up and cool down).

Aaron Johnson
Aaron Johnson

People say they don't have to change their rear diff fluid, even though service manual says every 30,000 miles.

Chesley Western
Chesley Western

i always love this stuff, tells me how to take care of my truck so itll take care of me! thanks for the info guys!!!

William Farrar
William Farrar

most people never plug their trucks in, let them warm up or let them idle down before shutting it off. i always did everything, even in the summer time. it may be hot out but you should still let the engine run for at least 5 min to lube the bearings and turbo up

crs55
crs55

Diesel fuel used to clean out an old engine case built with pot metal and then it starts like new but this but this diesel fuel is now unused able.  So what is the easy way to clean it up so can still be used?

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