It used to be that you only had to hoof it down the road for gas – or diesel – if you forgot to fill the tank and ran out of gas (or diesel). Now you can have a full tank – of diesel – and still be hoofing it, if you forgot to top off the DEF tank.
More finely, limping it.
In order to encourage you to never let the DEF tank run low, diesel-powered vehicles equipped with DEF tanks, like the 2025 Ram 2500 I am test driving this week, have “technology” that limits the vehicle’s speed to 5 MPH – about as fast as a man can walk – if you let the DEF tank run down to empty run empty. THat’s as fast as the vehicle will go until you pour in some DEF.
But what is DEF?
The acronym stands for Diesel Exhaust Fluid and that’s what’s in the tank. The second one. DEF is part of the emissions control system that afflicts all new diesel-powered vehicles, which isn’t many because all of this emissions rigamarole has demolished most of the reasons that motivated people to buy a diesel engine over a gas engine. Diesels were once simpler than gas engines and that meant they usually required less maintenance (because there was less to maintain) and cost less to maintain, too. Simplicity tended to increase longevity as well and this is why those who need a long-haul engine that will stand up for hundreds of thousands of miles prefer diesels.
Or at least, preferred them.
Diesels also used to have the advantage of being less expensive to run because diesel fuel cost less than gas once-upon-a-time and because – as most people know – diesel engines generally used much less fuel to propel a vehicle a given distance. Neither is true anymore. Diesel fuel costs more than gas now – not because it’s expensive but because government is – and the fuel-economy difference is now so marginal – about 5-7 MPG is typical – that it is not enough to counterbalance the much-higher cost of buying a “clean” (that is, government compliant) diesel engine, which typically adds thousands to the price of the vehicle (if it’s even available).
In the case of the ’25 Ram 2500, it adds $12,595 to the truck’s MSRP. You do get 1,075 ft.-lbs. of torque, which allows for massive towing capability. But there’s little, if any fuel efficiency/operating cost advantage vs. the gas V8 that’s standard in this truck.
Especially when you factor in the costs of the DEF. Note the plural.
The first cost is of course the cost of the DEF itself – about $16 for 2.5 gallons at my local auto parts place. That will fill about half of the Ram’s DEF tank, which holds about 5 gallons. So, it would cost about $30 to fill the tank. How often do you have to fill the tank? Apparently, about once every 8,000 miles, depending on how you drive. If you drive aggressively – that is if you use the engine’s 1,075 ft.-lbs. of torque regularly – you will probably need more DEF sooner. 
Having to spend $30 every 8,000 miles or so is not a huge cost but it does add to the cost of owning – and driving – a diesel-powered vehicle that eats away at the former savings one enjoyed by owning and driving a diesel-powered vehicle.
Let’s say you drive such that you need to fill the DEF tank once every other month. That’s about $180 annually – which works out to about $1,000 or so over five years.
The bigger cost, though, is the hassle.
While DEF isn’t very hard to find, you do have to find it when you need it – and you didn’t use to have to need it. Now you are forced to need it because if you don’t get it and the tank runs out, the vehicle will kaput itself, basically. Imagine being out on the highway – maybe towing something behind you – when the system punishes you for not being a Good Citizen by restricting the vehicle’s speed to 5 MPH. This would be dangerous as well as a hassle. But that cost is on you, Citizen – just the same as the time cost of having to wait for a “fast” charge if you own an EV.
They – the government – says DEF is a necessary thing for “emissions” reasons. The DEF – which is urea, basically – gets sprayed into the exhaust stream and this causes a catalytic reaction that makes diesel exhaust “cleaner.” How much – and whether this has any meaningful benefit – is another matter. What it does for sure is make owning a diesel powered vehicle more expensive and more of a hassle and that appears to be the real benefit, from a certain point-of-view.
From the Green – i.e., red – point-of-view.
Have you noticed that you can no longer buy any new car equipped with a diesel engine? As recently as ten years ago, there were many such – including diesel-powered versions of pretty much every vehicle sold by VW. Some of the latter – such as the TDI diesel powered versions of the Jetta and Golf – could be purchased for about $22,000. They achieved 50-something MPG on the highway and had full-tank ranges of 700 miles or more. There were also diesel-powered Chevys, such as the Malibu – as well as diesel-powered Mercedes and BMWs that were similarly long legged. I test drove a Mercedes diesel-engined sedan that made the trip from my place in SW Virginia near Roanoke to Raleigh, NC and back without stopping for diesel (or DEF) once. 
They are all gone now. Not for lack of market demand but on account of government demands. VW was treated as if it had been caught in a vast scheme of pederasty for programming the software that ran its TDI-powered vehicles to pass government emissions certification tests. It took ultra-pedantic examination of the vehicle’s exhaust to discover a slight – a fractional and momentary – increase in these vehicles’ “emissions” under wide-open-throttle operation. No actual harm-done was ever substantiated.
But an excuse was found.
The diesel engine – not just VW’s – was targeted not because of its emissions but rather because of its efficiency. A diesel-powered car with a 700 mile range that cost half as much as $50,000 EV that maybe went 250 miles was an intolerable point-of-comparison. Something had to be done. More finely, something had to be found.
And it was.
Diesels have vanished altogether from the passenger car marketplace in this country (which is no longer a market since it is managed and controlled by the government) and they are being pushed off the truck market via the death of a thousand small cuts, each one bleeding away the diesel engine’s former advantages and appeal by just a little bit until – at last – there’s no longer any advantage or appeal to owning one.
At which point, the government will be able to claim there’s no longer a “market” for them and that’s why they’re all gone.
. . .
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Consider this… I’ve long wondered about the apparent government disdain for diesel engines. The diesel engine can run on many fuels, including self made fuel from old cooking oils which are easily available from many restaurants. We can’t have a transportation device that is perfect for self reliance now can we?
WHY does anybody at all even BUY a brand new car (<10-30years) at all any more since all the gubbermint strangulation? Everyone should be stashing gold and silver so their money looks spent (and you actually save it) and then you sell it when you need an engine overhaul. We can also write our congressmutts and ask them to lay off with making citizen decisions for us. Cars will last a million miles with enuf maintenance. Didn't used to be worth the trouble but now it is.
Global Fertilizer Market Thrown In Chaos After Mideast War Shutters Iran Urea Production
“‘Iran has shut down seven of its urea and ammonia plants,’ said Mark Milam, senior editor for fertilizers at Independent Commodity Intelligence Services, over concerns that they could be potential Israeli targets.”
“Josh Linville, vice president of fertilizers at commodities analysis firm StoneX, said that attacks on the country’s natural gas infrastructure – which is used in the production of urea – is also keeping operations offline,” Ward reported.
“Iran was the third-largest urea exporter in 2024, according to StoneX, with export volumes of around 4.5 million tons – about the size of China’s. The country has a production capacity of around 8.9 million tons a year, Milam added, serving markets in Turkey, Brazil and Argentina, among others. It is also an exporter of ammonia.”
“In addition to knocking Iranian urea production offline, the attacks also brought Egypt’s operations to a standstill,” Ward reported. “Israel reduced its natural gas flows to the country on Friday, prompting Egypt to cease production.”
Urea production in Iran and Egypt has been shut down. China produces another 1/3 of global exports. IIRC, Russia is also a major producer of Urea (which is the main component of DEF).
It looks like that shitty little genocidal country that also happens to be the “Jewish Homeland” is about to cause a major global shortage of DEF and fertilizers. That would be very bad news for the US whose economy depends so much on trucking, diesel and DEF.
That’s why they switched to electronic throttle etc (instead of cable throttle) –so they can control your car.
“…which is no longer a market since it is managed and controlled by the government..”
Which now applies to basically every single ‘market’ one can think of.
The only real ‘free’ markets that still exist are the ones on the Dark Net, selling drugs.
Somehow even though they’re not ‘regulated’, so there is no ‘customer protection’ by the ‘benevolent’ government agencies, they continue to have plenty of customers.
Funny how that works.
I love my 2014 Cayenne Diesel. Tons of torque, 34 mag or more on the road. 29 gallon tank.
I used to refill the pee tank but the sensor can be spoofed with a resistor. I used a 10k but probably anything will work. The computer thinks the DEF tank is perpetually half full.
I was worried there might be other sensors in the system that would detect loss of DEF injection but I’ve been running the DEF on empty for 2 years now and it seems quite happy.
I imagine that the delete kit would make it even better by removing the section of the exhaust pipe where the injection port is, maybe one day.
I’d like to remove the tank. It sits under the spare tire the space could definitely be put to better use.
I love it, Alex. If you can pull-off just some little things like this, you are the Resistance.
In the heavy equipment industry, the addition of DEF to fuel and hydraulic tanks has become a notorious problem. It’s not an easily remedied or inexpensive problem either, especially if the equipment is run afterwards.
I’m quite happy my backhoe is old and much simpler than the technological nightmares being produced today.
We’re going to have SCR catalysts in gasoline engines at some point. SCR, using the urea injection, is used to reduce nitrous oxide emissions. This happens when engines run lean, like diesels, which run lean most of the time. Engines like Mazda’s Skyactive-X which can run lean, also make NOx like a diesel.
This is simple physics. Lean burn = high temperature = more chances of NOx. Rich burn = lower temperature = more hydrocarbon emissions (meaning, more co2/mile). The regulators are forcing less co2/mile and also less NOx, which means very expensive systems.
There is absolutely zero reason for a car whose DEF tank runs low to limit power. The regulators wanted the engine to shut down completely, but auto companies managed to get a concession, allowing the car to limp at 5mph to get that tank filled. These people are petty tyrants.
My Dad took his Diesel Range Rover down to Fl to use down there. I’ll find a shop that does deletes down there for it
With Barry the Limp Wristed Queen and Pedo Peter gone, and the Legend of Zeldin scaling back regs, should be a lot easier to delete and tune his ‘18 without getting Hut!hut!hutted over it
Why don’t the car companies steal a page from Mobil’s playbook? Remember how, back in the 1970s and 80s, Mobil would buy these full page ads in major papers critiquing gov’t policies and how they impacted Americans? Why don’t the car companies do something similar now?
‘in the 1970s and 80s, Mobil would buy these full page ads in major papers’ — MarkyMark
During Tall Paul Volcker’s tenure at the Federal Reserve, when the prime rate hit 21 percent, an infrastructure-oriented company published a full-page ad in protest. It featured twin skull-and-crossbones symbols, about six inches high, with big black headline type proclaiming ‘21% Interest Rates Kill.’
No one does that now, when Big Gov can shut your ass down. Even Harvard (est. 1636) might be shut down if the Trump regime gets its way.
So businesses keep their heads down, ‘comply,’ and hope that the idle whims of their despotic regulators don’t become even more insane. As an article about Venezuela’s caudillo regime puts it, ‘It’s an old chavista tactic: when they can’t control reality, they go after those who describe it.’
https://tinyurl.com/53x2v4kt
Trump is a classic caudillo. Anyone who confronts him, domestically or internationally, quickly will be confronted by an onslaught of decrees, and maybe even a nuclear-armed fleet of B2 bombers, like the ones just flown to Guam to menace Iran.
Welcome to Planet of the Apes, comrades: submit to the alpha male primate, or get your skull smashed in with a club.
Just a geographic suggestion. I believe B-2 bombers were sent to Diego Garcia, smack dab in the middle of the Indian Ocean (the British confiscated Chagos Archipelago) thus quite proximate to Iran.
Guam, just east of the Philippine Sea in the western Pacific was a major staging area for B-52 bombers during the Vietnam war….ummm..(Conflict).
Mobil was a big underwriter on PBS. I remember “Mystery” in particular, but there may have been others.
Back when Audi had their Q5 and Q7 TDI drivetrains, DEF was brand new tech. So new that Audi didn’t know what to do about it. At first they required the driver only refill at the dealer so that the technician could reset the DEF tank indicator! But even after they “allowed” owners to refill themselves, if you let the tank run dry it would not start.
From the owner’s manual…
AdBlue 600 mi (1000 km) Refill Ad Blue! No restart in 600 mi (1000 km) ! See owner’s manual
This message appears when there is only enough Ad Blue left to drive the distance indicated in the instrument cluster. Fill the AdBlue. Otherwise the engine will not start again if you stop it once the distance indicated has been driven.
Can’t even limp home. I wonder if it will just stop dead at a red light or otherwise leave you stranded on the side of the road?
Not only that, but here’s a bunch of warnings:
AdBlue can irritate the skin, eyes and respiratory system. If there is contact with the fluid, flush immediately with plenty of water. Consult a physician if necessary.
Of course that’s a bunch of lawyerese, and the same holds true for gasoline, but normally you don’t buy gas in a jug at Walmart.
Ad Blue attacks surfaces such as painted vehicle components, plastic and carpet. Remove the fluid as quickly as possible with a damp cloth and plenty of cold water. If the AdBlue has already crystallized, use warm water and a sponge. Ad Blue residue that is not removed will crystallize and can damage the affected surface.
No wonder most of the Ram/Cummins drivers around here add a “delete kit” to their DEF system!
Diesel from crude oil is sometimes stinky stuff.
You can use peanut oil, the original diesel fuel for Rudolf Diesel’s engine.
Canola oil works. Used oil from restaurants does work too.
The exhaust will have a French fries aroma.
The gov should mandate that all diesel fuel be plant-based, i.e. from peanuts.
The exhaust will have a roasted peanut aroma.
Refine crude to bunker fuel and ships can burn it in the Fairbanks Morse engines.
No DEF necessary for a Fairbanks Morse engine.
Fairbanks Morse can manufacture small diesel engines that won’t need DEF, install them in cars and trucks, they’ll sell.
Don’t accidentally get DEF in the diesel tank either.
It will crystallize and destroy the entire fuel system.
Can’t you just piss in the tank? When DEF first came out, it was based on sheeps urine, and I thought the blue color was just to throw us off.
Even google says it’s urea and deionized water.
Anyone tried mixing piss and distilled water and / or deionized water and got away with it?
Of course googuhl shills for DEF.
Hi Steve,
I was thinking of just that – but it’s not my truck! I wish I had the means to just buy one of these rigs for “testing purposes” – as Whistlin’ Diesel does. But I am just a poor boy though my story’s seldom told…
I’m not a big Simon and Garfunkel fan but The Boxer is sheer musical genius. Simon’s guitar and voice and beautiful but Garfunkel’s voice is an incredible instrument in itself.
The DEF tanks probably have sensors to check the Urea concentration of the contents.
Another Patent!
@Eric – Is it true that the DEF tank replaces the spare tire in the big, late model Mercedes sedans with diesel engines?
My wife has an extensive biochemistry background, and the DEF numbers don’t make sense to her.
Hey Steve,
I’d imagine the salts present in urine might cause problems for the system, but in a pinch, if the vehicle were to leave me stranded or driving 5 MPH, I might try anyway.
The goals and actions of the Enviro-Commies are bad enough. What’s really grating is their smarmy way of doing things. “Oh, we didn’t outlaw anything. It’s just that the old ways don’t meet the new regs.”
A murderous thief is more honest, “Your money or your life.” They would never take the attitude of, “what? little ol’ me?”
Enviro-Commies and Juedo-Marxists, cut from the same cloth.
I suspect that when you’re towing a heavy load the diesel will be way ahead of the gas engine regarding fuel economy. Listening to buddies comparing fuel economy when towing bears this out.
Of course if you want get a heart attack just price out the converter on a diesel powered truck.
Once the warranty runs out you can get your local tuner to “fix” it so the DEF system doesn’t operate, just don’t tell anyone cause that’s illegal…
… meaning don’t post your dark little secret on Faceborg, which is crawling with DMV spies and informers.
https://tinyurl.com/b23kt6ey
Hi Jim. Also don’t list it in ads that you done it or better yet re-tune it back to stock when you sell it and keep any parts you remove so as to reinstall when selling it. GovCo gets angry if they catch you…
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Hi Ken,
I’m not following! We do have a slide thing to establish you’re not a bot. Are you encountering something else?
Hey, Kinda sounded like I was blaming you—–when reading it back—— I’m not, it was meant as a heads up. . That is the message I got from You Tube. Required 3-4 refreshes to get around it.
In fact, Suspiciously,,, it allowed me to view the video when I sent this message. Youtube even defeated Copy and Paste and forced me to type from memory which is tough for aged brain. No insult intended,,, in fact I look forward to reading your column every morning,,, one of the few sources of rational thought left on the internet.
Thanks, Ken!
I have been trying to rebuild my YouTube channel because while I like Rumble, they totally screw the content creator. You can have 10,000 views (single vid) and get not even a fraction of a cent in payment. I did okay on YouTube before “COVID” but got demonetized for my Diaper Reporting. Now I’m trying to get back to where I was. Again, I appreciate the heads up (and the kind words)!
One solution Eric would be to put the content on both sites but post the “unapproved” content only on Rumble. The sheeple get confused when they hear the truth on YouTube…..