9 Worst Things You Can Do to a Diesel Engine

/ 9 Worst Things You Can Do to a Diesel Engine #1  

MapleLeafFarmer

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9 Worst Things You Can Do to a Diesel Engine
  • Letting the fuel tank run low. ...
  • not keeping up with oil changes. ...
  • Using the wrong type of fuel. ...
  • Cold starts without proper warm-up. ...
  • Overloading the engine. ...
  • Skipping coolant changes. ...
  • Neglecting filter maintenance. ...
  • Ignoring warning lights. ...
  • Failing to keep the engine clean.
FWIW: the following came from a diesel tech course put out by UTI earlier this year. Part of their 45 week diesel training course


Not keeping up with oil changes
Skipping oil changes is one of the fastest ways to wear down your diesel engine. Over time, engine oil loses its lubricity as it breaks down from heat, pressure and contamination. As the oil ages, it becomes less effective at reducing friction, absorbing heat and suspending harmful particles. In diesel engines, where internal pressures and operating temperatures are often higher than in gas engines, this breakdown happens even faster.

Contaminants like soot, fuel dilution and metal particles can accelerate wear on vital components such as bearings, pistons and turbochargers. Sticking to a regular oil change schedule based on your engine’s workload and manufacturer guidelines is essential to maintaining performance, preventing costly damage and extending the life of your diesel engine.

Letting the fuel tank run low
Running a diesel engine on a near-empty tank can cause serious problems. Sediment and contaminants naturally settle at the bottom of the tank, and when fuel levels drop, these particles can be pulled into the fuel system, clogging filters, damaging injectors and reducing fuel flow.

But the bigger concern is air entering the fuel system. Diesel systems rely on consistent pressure and flow, and introducing air can lead to hard starts, engine misfires and, in some cases, injector damage due to improper lubrication and cooling.

Low fuel levels can also increase the risk of moisture buildup, especially in environments with temperature swings. The more space in the tank, the more room for condensation to form, which can lead to microbial growth and fuel degradation. To prevent these issues, it’s best to keep your diesel tank at least a quarter full whenever possible.

Using the wrong type of fuel
Diesel engines require diesel fuel, plain and simple. Accidentally using gasoline in a diesel engine can cause severe damage. Gasoline lacks the lubricating properties that diesel fuel provides, which are essential for protecting high-pressure components like fuel injectors and the fuel pump. Without proper lubrication, these parts can quickly overheat, seize or wear prematurely.

In addition, gasoline combusts differently than diesel. It can ignite too early in the combustion cycle, causing engine knocking, misfires and potentially catastrophic damage to pistons and valves. Even a small amount of gasoline can disrupt the entire fuel system and may require a full flush to prevent long-term issues.

Using the wrong grade of diesel (e.g., #1 vs. #2, or off-road vs. on-road diesel) can also impact engine performance and emissions compliance. Always double-check the pump before refueling and make sure you understand which fuel type your vehicle or equipment requires based on climate, application and manufacturer recommendations.

Cold starts without proper warm-up
Diesel engines don’t respond well to cold starts, especially in freezing temperatures. Starting the engine without allowing it to warm up can cause incomplete combustion, rough idling and excessive engine wear. Cold temperatures thicken both diesel fuel and engine oil, making them harder to circulate through the engine. Thickened oil struggles to reach critical components quickly, increasing friction and wear during those first few moments after startup.

Diesel fuel can also gel in extremely low temperatures, restricting flow to the injectors and fuel pump, which may lead to hard starts or stalling. This is especially problematic without the right winter blend or fuel additives.

To protect your engine, use block heaters, glow plugs or intake heaters to warm the engine and fuel system before starting. Letting the engine idle for a few minutes gives oil time to circulate and ensures the fuel reaches the right temperature for proper combustion, reducing stress and wear on internal parts.

Overloading the engine
Pushing your diesel engine beyond its limits by hauling loads heavier than it’s rated for can cause excessive stress and long-term damage. Overloading increases engine workload, leading to higher operating temperatures, reduced fuel efficiency and accelerated wear on critical components.

When the engine is forced to work harder than intended, internal components like pistons, bearings and valves experience more friction and pressure, which shortens their lifespan. The added strain can also affect the transmission, drivetrain, suspension and braking systems, putting your entire vehicle at risk.

Prolonged overloading can even lead to thermal breakdown of engine oil, decreasing its effectiveness and further compounding wear. To ensure safe and efficient operation, always stick to your vehicle’s recommended weight limits, including the gross vehicle weight rating (GVWR) and tow rating, and evenly distribute loads to avoid unnecessary stress on the engine and chassis.

Skipping coolant changes
Coolant helps regulate engine temperature and prevent internal corrosion, making it critical for diesel engine health. Skipping coolant flushes allows the coolant to degrade over time, reducing its effectiveness and exposing the cooling system to serious risks.

When coolant breaks down, it loses its anti-corrosion properties and can become acidic, leading to rust, scale buildup and clogged coolant passages. This restricts flow and reduces heat transfer, causing the engine to overheat. Degraded coolant can also damage the water pump, radiator and head gasket, potentially resulting in costly repairs.

Signs of bad or failing coolant include:
  • Rusty, sludgy or discolored coolant
  • Persistent overheating
  • Coolant leaks or low levels
  • Sweet smell under the hood (indicative of a leak)
Regularly flushing and replacing coolant based on your engine’s maintenance schedule helps keep temperatures stable, protects vital components and extends the life of your diesel engine.

Neglecting filter maintenance
Diesel engines rely heavily on clean air and fuel, making filter maintenance critical. Dirty air filters reduce airflow, leading to poor combustion, increased fuel consumption and power loss. Clogged fuel filters can restrict fuel flow, starving the engine, damaging injectors and causing hard starts or stalling.

Over time, neglecting filter maintenance doesn't just impact performance; it can lead to long-term engine damage. Insufficient air or fuel flow can result in incomplete combustion, which produces more soot and unburnt fuel. This buildup can clog exhaust gas recirculation (EGR) valves and coolers, reducing their efficiency and contributing to higher emissions, rough idling and even EGR system failure.

In severe cases, dirty filters can lead to increased crankcase pressure and contamination of engine oil, accelerating internal wear.

Ignoring warning lights
Dashboard warning lights are there for a reason. Ignoring signs like the check engine light or glow plug warning can turn minor issues into major repairs. Address problems as soon as they appear to prevent further damage and avoid expensive breakdowns.

Failing to keep the engine clean
Dirt, grime and oil buildup can hide small leaks and lead to overheating or contamination. A clean engine compartment helps you spot issues early and ensures proper airflow for cooling. Regular cleaning also extends the life of hoses, belts and seals.
 
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/ 9 Worst Things You Can Do to a Diesel Engine
  • Thread Starter
#3  
How about using starting fluid to fire it up? o_O
I was taught that only applies to diesels with glow plugs or pre-heat systems doesn't it??
used sparingly has been a staple for century hasn't it?
its still sold today for use on diesels by many manufacturers like Lucas etc..... approved for use on diesels.

happy to be proven wrong though.
Cheers
 
/ 9 Worst Things You Can Do to a Diesel Engine #5  
Letting the fuel tank run low
Running a diesel engine on a near-empty tank can cause serious problems. Sediment and contaminants naturally settle at the bottom of the tank, and when fuel levels drop, these particles can be pulled into the fuel system, clogging filters, damaging injectors and reducing fuel flow.

But the bigger concern is air entering the fuel system. Diesel systems rely on consistent pressure and flow, and introducing air can lead to hard starts, engine misfires and, in some cases, injector damage due to improper lubrication and cooling.

Low fuel levels can also increase the risk of moisture buildup, especially in environments with temperature swings. The more space in the tank, the more room for condensation to form, which can lead to microbial growth and fuel degradation. To prevent these issues, it’s best to keep your diesel tank at least a quarter full whenever possible.

I run my truck to the fuel light every tank for the most part. I figure if you always suck all the fuel out then there won't be time for lots of sediment to build up.

I will also say that when I ran a big excavator too low I was changing muddy fuel filters at a very inopportune time....
 
/ 9 Worst Things You Can Do to a Diesel Engine
  • Thread Starter
#6  
I run my truck to the fuel light every tank for the most part. I figure if you always suck all the fuel out then there won't be time for lots of sediment to build up.

I will also say that when I ran a big excavator too low I was changing muddy fuel filters at a very inopportune time....
I tend to run my down as well thinking that get the nastiness into the filters then swap out the filters regularly versus having fungus and bacteria living in the transition zone of the fuel tanks or the sediment and solids building up on the bottom.
But generally if storing (vs using) then I would fill and treat.
So for me it depends.
 
/ 9 Worst Things You Can Do to a Diesel Engine #7  
Isn't the fuel outlet on most systems at the bottom of the tank? Why doesn't whatever is on the bottom of the tank automatically get fed into the engine first?
 
/ 9 Worst Things You Can Do to a Diesel Engine #8  
Emergency Hospital Generators go pedal to the metal so as to transfer power within the allotted 10 seconds… we do have round the clock block warmers to keep the coolant hot.
 
/ 9 Worst Things You Can Do to a Diesel Engine #9  
Using the wrong grade of diesel (e.g., #1 vs. #2, or off-road vs. on-road diesel) can also impact engine performance and emissions compliance. Always double-check the pump before refueling and make sure you understand which fuel type your vehicle or equipment requires based on climate, application and manufacturer recommendations.
That sounds like something AI would come up with.

How would a diesel engine know or care if the fuel is red or not??
But I wouldn't mind seeing idling on the list.
 
/ 9 Worst Things You Can Do to a Diesel Engine #10  
Emergency Hospital Generators go pedal to the metal so as to transfer power within the allotted 10 seconds… we do have round the clock block warmers to keep the coolant hot.
In this case, performance t r u m p s longevity, and hopefully engine replacement is budgeted in due to the harsh conditions.
 
/ 9 Worst Things You Can Do to a Diesel Engine #12  
Using the wrong grade of diesel (e.g., #1 vs. #2, or off-road vs. on-road diesel) can also impact engine performance and emissions compliance.

While #1 & #2 fuel will effect "performance" as the #2 has more paraffin in it to burn, hence more power and won't effect emissions ...but like was stated above, only difference in off-road vs on-road is the dye, and has NO discernable difference in the two categories mentioned, however DOT may cut back your wallet a bit if they catch you with dyed diesel in a road vehicle ...


Letting the fuel tank run low
Running a diesel engine on a near-empty tank can cause serious problems. Sediment and contaminants naturally settle at the bottom of the tank, and when fuel levels drop, these particles can be pulled into the fuel system, clogging filters, damaging injectors and reducing fuel flow.

Only way that could possibly happen is if water got through, besides your fuel pump could also be harmed running water through it, that's why fuel filters have a bowl to collect the water, some have a drain too ... The filter will clog up with sediment, and actually filters "better" the more crud it has caught, until no more fuel will go through ... And water is heavier than fuel, so like mentioned it sits on the bottom of the tank (and fuel bowl), which smaller tractors have bottom gravity fed supply lines ... My Semi-truck truck has an actual pickup tube, and leaves about 10+ gallons in the bottom ...

We also go 60,000 miles on oil changes on our semi-trucks ...

The coolant I use in my tractor says "good for 1.5 MILLION MILES"! :cool: 😂

IMG_20240104_092206119.jpg


But, I change it every two years!

IMG_20240104_092224178.jpg
 
/ 9 Worst Things You Can Do to a Diesel Engine #13  
That list is pretty obvious, but here’s 2 others not on the list:

Lugging: lugging a diesel engine can be harmful as it may lead to increased wear and potential damage to engine components. It's generally better to operate at higher RPMs to ensure the engine runs efficiently and avoids stress.

I see this frequently. I see a lot of operators run at a lower RPM than they should.


Here’s another big one not mentioned:

Shutting off a hot turbocharged diesel: Shutting down a diesel engine with a turbocharger over 1200 degrees instantly stops the oil flowing through the turbo bearings. The oil can actually start “coking” in the bearings.

If you were to rev up your engine and then shut it off, it will cause damage and wear to the turbocharger as the oil pressure drops with it is still spinning at very high RPMs. Modern turbochargers can have turbine speeds above 100,000 rpm! Even the older models will have RPMs ranging from 40,000 to 60,000.

At these speeds, lubrication of the turbocharger bearings is super important for your turbo to last. The turbo must be allowed to spin down before the oil vacates. If not, you will be putting another turbo on before long.
 
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/ 9 Worst Things You Can Do to a Diesel Engine #14  
And the newer ones with DPF ... Idling ... Will plug up the DPF much faster than either turning it off, or WORKING it! Neither of mine can be over revved, they have a governor on them ...

I see lots of semi-trucks idling over night, then the HUGE clouds of smoke the first mile or two as they regen mostly cleaning out the DPF ... But there is a very fine layer of ash left over from each regen which burns off the soot, that builds up, and causes more frequent regens, and will eventually need to be cleaned or replaced, resulting in down time and extra money spent.
 
/ 9 Worst Things You Can Do to a Diesel Engine #16  
And the newer ones with DPF ... Idling ... Will plug up the DPF much faster than either turning it off, or WORKING it!
As I recall, when reading up on such things after getting a Pete with a 3406B (no emissions, obviously), the rings weren't even made to seal at idle.

That may only be true for the older designs, but I don't needlessly idle anything if at all possible. My '17 Ram 3500 has 11 idle hours on it, my '21 Ram 1500 (gasser) has one.
 
/ 9 Worst Things You Can Do to a Diesel Engine #17  
We, as a company had Auxiliary Power Units (APU's) installed at Kenworth prior to taking delivery ...

If the drivers will use them there is a huge savings in fuel, they roughly burn 1-2 gallons of diesel per "night" whereas my 15 liter Cummins burns .8-1.2 gallons of fuel per HOUR at idle ... Over the course of 4 years they more than make up the initial $13K cost ...

PLUS, they share the same coolant as the truck engine, so when I start the 15 liter the coolant is already 75°-125°F, so starts easier in the winter, and less warm up needed, besides it keeps the batteries topped up ... Yet many drivers insist on idling there trucks all night, even like last night in South Carolina it was about 70° when I went to bed, 52° when I got up ... I was snug in my sleeper, without even needing the heater in the APU! Or they leave it idling while fueling, then wander inside for another 15 minutes ...
 
/ 9 Worst Things You Can Do to a Diesel Engine #19  
as with any machine, single use owner/operators from new helps longevity if they know what they're doing
Aside from how to operate things, correct break-in and early first oil changes can really help with longevity.

I tend to overkill, bringing new vehicles home on a trailer, then putting them on the lift to check fluid levels (which are rarely correct) and install magnetic level plugs wherever possible.

Next is the diff gear break-in, following gear manufacturers' guidelines. With those first painful 100 miles done, and the brakes properly bedded in, I switch to the vehicle manufacturer's recommended break-in.

Before that's over they get a first oil change at 500 or so miles, and new diff fluid. The latter has saved a couple of diffs from an early demise.

Well, you get the idea, I treat them all as forever-vehicles, which they never end up being. Heck, I've sold several with under 1,000 miles on them.
 
/ 9 Worst Things You Can Do to a Diesel Engine #20  
what's the current new vehicle 1st oil change since factory? 4-6k? can't imagine
 
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