There are very few diesel engine makers left in the nation today. What that means is that these companies are going to be on both the best and worst diesel engine lists.
Diesels, even on their worst days, are often considered far better than a gas engine. But mistakes have been made over the years and there are still diesel engines to avoid.
To learn which models of diesel engines to avoid, just continue to read our article. It provides a list of as many as can be found. Rating engines are subjective though as even bad models series had some very good engines that still run today.
Putting together a list like this is not always easy to do. It is possible to upset someone who has nothing but a very good experience with the models on this list. But according to popular opinion, these are some of the engines to avoid:
1. International- VT-265, VT-265, VT-335, VT-365 Series (Became PowerStroke 6.0L)
These engines were highly underpowered. Originally, this model series was a 6-cylinder motor but someone at International got the bright idea to make newer models 4-cylinders. The idea did not work.
2. CAT 3116-
This was a good engine in many respects but it had one glaring problem. It was very difficult to work on and time the fuel system. Also, it came off the assembly very underpowered as well.
3. Cummins ISX-
This model was to replace the popular N-14 and it was to be a new and improved model over that earlier engine. It did not work out that way as the design created many engine failures. Plus, it was a very complicated engine design that hurt Cummins's reputation
4. Detroit- All old two-stroke Series 50, V-71 or V-92
You can say the same thing for all older engines as we will for these series. These older diesels are just too old and technology has left them in the dust. These older models are just past their prime and shouldn’t be used anymore.
5. Navistar- MaxxForce 13
Not a well-designed engine and they came with a lot of problems. They were almost always in the repair shop for major work. You would get a better ride out of the Maxxforce 10
6. Cummins- 53 block
This model should never have been made. It cracked easier than a walnut and did not perform up to expectations.
Diesel engines are found in a variety of vehicles. From the early Nissan pick-up trucks of the 1980s to the big rigs to emergency and similar vehicles. Not every company that made a diesel engine hit a home run.
Some of the following worst engines on this list come from highly reputable automakers.
1. BMW M47
This was a popular diesel engine in Europe. However, because it was a modern engine and had a very complicated design, it had many components that would fail regularly. One of those failure points was that it could not keep its cool.
It overheated all the time, even in the winter months.
2. Cummins R2.8
Made in China, three dreaded words to read or hear anywhere in the world. Cummins may have sent the specs but the Chinese manufacturing plant used inferior metals and the results were not good.
Most people may not have heard of this engine as it was sold mainly in Asia but it came to America as a crate engine. Not being well-known is a sign of how bad it really was.
3. Fiat 1.9 Liter JTD
The first generation had most of the problems. It was underpowered, unrefined, and unreliable. Future generations of this motor corrected most of the mistakes made initially but this motor remained a non-hardworking motor that had limited applications.
4. VW EA189
If you heard of Dieselgate, this was the engine model that created that scandal. It was not a very good emissions motor and VW did not fix the problem. They just found a way to cheat the system while letting the problems remain in place.
You can read about dieselgate at this link and see what this motor did to VW.
5. Toyota D4D 3.0 Liter
This company is a very good engine and car builder. However, for some unknown reason, the company’s engineers could not master the diesel engine. The main cause that made this one of the worst diesel engines to own was the injectors.
They got bad very quickly and if not repaired would destroy the engine. What made things worse was that Toyota did not take this problem seriously. They issued spotty recalls and lost some of their market share to Ford.
6. Ford 6.0 Liter Powerstroke
This is a good car and truck building company and they have produced some great engines over the years. However, something went wrong in the design portion when making this motor.
Ford used the wrong head studs and turned what could have been a good motor into one you should avoid.
7. Toyota 5L
This company saw that it had a problem with the 2L motor they placed in their Hilux truck models. So they tried to improve on that earlier design to give the Hilux more power and speed.
They came up with this engine but it had problems. They overheated a lot, especially when they were used in hotter climates.
8. Mitsubishi 4M40
It is feast or famine with this engine maker. This company is known for making some of the best and some of the worst diesel engines out there. Design flaws were the culprits in this case.
Mitsubishi designed aluminum heads that could not withstand the heat or the pressure. This engine had many heads crack under pressure making this one of the worst diesel engines you could buy.
9. Land Rover TD5
This engine was developed before BMW took over the company. But it was not in production until BMW gave the go-ahead. They should have waited a little longer to see if this engine would perform as it should.
It didn’t as the ECU had a way of sucking oil into it through the harness. Once that took place the ECU was destroyed. This was a very nice 5-cylinder design that came with lots of power except for this major flaw.
10. Oldsmobile V8 Diesel
Oldsmobile tried to convert a gas small block motor into a small block diesel-powered engine. It did not work and the head bolts continuously failed on this engine.
This failure certainly hindered any progression in developing more diesel engines for a time.
There is going to be a wide range of opinions on this topic. One person called the CAT 3208 the best engine ever made by that company and the next person who responded called it the utter worst.
Then one review site said that the Detroit engines were top-of-the-line and the best, while another person said they were some of the worst. This is the major problem with creating these lists.
The experience you have with a specific motor will determine your opinion about which one goes on the best and which one goes on the worst diesel engine list. But here goes:
1. The CAT engines
One reason they got out of the on-highway engine business was that they could not master the emissions problems their engines had. Two of the most embarrassing moments CAT had was when they made the Acert motors and the dual turbo models.
2. Cummins- twin overhead cam motors ISX
Not a very good design and it had major problems. One owner was able to avoid a lot of major problems when he shortened his oil changes to 20,000 kilometers over the recommended 40,000 to 50,000 oil change frequency.
One owner said it was the best engine he had.
3. Mercedes/Sterling/Freightliner - small block
It seems that both Sterling & Freightliner experimented with a small block diesel engine from Mercedes. It worked in the lower class of trucks but not in anything that was going to be hardworking.
4. Volvo/Mack- the 12L & 13L engines
Not the best designed motors you could find. One of the biggest problems was the fact that an owner had trouble finding a mechanic to work on them. This made these motors very unpopular to say the best about them.
5. Detroit- 6V92 and a 8V92
Some older drivers claimed that these were not very good engines. And they stated that they would make very good boat anchors. We have heard all sides of this brand and you will have some people saying they are the worst and some people saying they are the best.
We will leave this list open so others can add the brands they hate. This is a purely subjective list based on experience more than mechanics.
1. The 6.0 Ford Turbo Diesel
The expectations for this motor were high. That is until they started to perform. What made this one of the worst Ford diesel engines produced was the fact it created very expensive repair bills.
It was very hard to maintain and you had to remove the cab to replace the injectors. Also, it was a fuel guzzler which turned many prospective buyers off. This was known as the 6.0 Powerstroke which could not meet emissions requirements and had design flaws.
2. Ford Lehman Diesel
An engine designed for boats and trawlers yet Ford put it in some of their trucks. This was a big mistake budget-wise as it ate the gas very quickly. This motor was always thirsty and built up a hefty fuel bill.
Also, it was an underpowered engine that just did not have what it takes to move a heavy truck.
3. Powerstroke 6.4 Turbo Diesel
When you base a newer engine on an older one with design and other problems, it stands to reason the newer engine will fail as well. This one was and it did.
What made things worse was that this engine was basically the same as the 6.0. The one main difference was that the 6.4 was given more power. Yet Ford did not solve the maintenance issue.
It was very expensive to repair. This is an improved motor over the 6.0 but the maintenance issues caused it to be one of the three worst diesel engines Ford designed.
If you are looking for which model years you need to avoid so you do not get stuck with one of these badly designed engines, just keep reading.
1. 2003 to 2007 Powerstroke 6.0L- the engines made during this time period suffered from turbo issues, O-ring failure as well as EGR issues. The worst years may have been 2004 to 2005.
2. 2011 to 2014 Powerstroke 6.7L- this was the Super Duty engine and the problems you would experience if you owned a Ford vehicle during these years were and are- EGR, turbo, and emission systems failed and the injection pump, ETG sensor, and cooler clogged
The safer years to buy a Ford diesel are:
1994 to 2004 7.3L Powerstroke
1999 to 2003 Ford Super Duty
2008 to 2010 Ford F250 or the Ford F-350
Every worst or best list is a matter of opinion. Which list does a motor gets placed on is if you get stuck with a lemon or you got one of these worst engine models that performed well?
Many owners liked brands that other owners did not like and vice versa. Some people overcame the problems that came with these engines by changing their maintenance schedules and oil change frequency.
Take the list for what it is intended to be, a list that makes you aware that not every top engine is without problems.