24 of the All-Time Worst Car Engines

Car engines are basically just air pumps, but they can be highly complex and very maintenance-intensive.

Deciding what makes a car engine good or bad is somewhat subjective, as some people are willing to sacrifice reliability for maximum power, and others might be the exact opposite.

That said, we think it’s fair to expect a certain level of reliability from an engine used in mass-produced cars.

The engines we’ve chosen for this list all have some design flaw, and we’ve included them based on owner complaints. Chances are not every unit made will have problems, but the odds are stacked against them.

Maintenance is key; even the most reliable engine will eventually fail if neglected.

Mazda Renesis 13B Rotary Engine

There was never any doubt that the Mazda Renesis Wankel engine belonged on this list. It has a severe drinking problem, chugging premium gas like it’s going out of style. It also burns oil at a rate that hasn’t been seen since the Kuwaiti oil field fires of 1991 (too soon?).

Worst of all, it chews through its apex seals and requires a complete rebuild every 50,000 miles. If you buy one, tell your local rotary engine specialist to give it a full bridgeport job when rebuilding it for that proper rotary braap-braap sound.

BMW S85 V10

Found in the E60 M5 and E63 M6, BMW’s S85 V10 engine has one of the best soundtracks we’ve ever heard, and with 507-hp, it packs a serious punch as well. Unfortunately, that’s the only nice things we have to say about it.

Rod bearings, valve cover gasket oil leaks, and throttle actuators are known problems with this engine, and each can cost thousands to fix. No wonder the M5 and M6 are so cheap these days.

Ford 3.8L V6

Ford used the 3.8-liter V6 engine in several models over the years, but you won’t find many cars with this engine on the road today. It’s infamous for blowing head gaskets, and the engine’s flawed design caused coolant leaks, leading to overheating and engine damage.

Since it was expensive to repair, most owners eventually got rid of the car rather than keep fixing it.

Subaru 2.0 & 2.5 Boxer

Subaru’s 2.0 and 2.5-liter engines, commonly found in performance models such as the WRX and Forester, are known for head gasket failures and oil consumption issues.

The boxer engines have a poor head gasket design, which causes frequent coolant leaks and overheating, resulting in expensive repairs. Both oil starvation and excessive oil consumption are common problems with these engines. Subarus are also very popular with tuners, and running bigger turbos and more boost certainly won’t make them any more reliable.

Triumph V8

Some gearheads say the Triumph V8 is the worst engine ever made. Triumph’s sports cars were traditionally fitted with four-cylinder engines, but when it launched the Stag, someone decided to use a V8. Triumph had access to the legendary Rover V8, but instead of using that, they built a V8 using two of its slant-fours.

It was a disaster, suffering from overheating and total engine failure. Many owners replaced the Triumph V8 with Ford or Buick units instead. Triumph never made another V8 engine after the Stag flopped spectacularly.

Ford Triton 5.4

Ford installed the Triton engine in millions of trucks, so including it on this list may seem controversial. Yes, plenty of satisfied owners have never experienced any problems with it. However, there’s no denying that it has also caused headaches for thousands of owners.

Sludge can build up in the oil passages, which in turn causes problems with the cam phasers for the variable valve timing and can lead to catastrophic failure. Engines made before 2003 also had a problem with the spark plugs being blown out.

Ford 4.2 V6

The 4.2-liter V6 engine is another problematic Ford unit. One of the models it was used in was the popular F-150 pickup truck. It suffers from various issues, but the most serious is the timing cover gasket failure.

When it fails, coolant leaks into the engine, which can cause severe engine damage. The 4.2 V6 engine is also known for excessive oil consumption. Repairing these issues can be expensive and, in many cases, not worth it.

GM 2.4 Ecotec

The GM 2.4-liter Ecotec engine is found in vehicles such as the Chevrolet Equinox and Buick Regal. It suffers from excessive oil consumption, which is made worse by the failure of the “Oil Pressure Warning” system, which is supposed to alert drivers to low oil levels.

It also has a problem with premature timing chain wear, which has caused the timing chain to fail, resulting in expensive repairs and potential engine damage.

Chevrolet Vega Aluminum Engine

Of all the cars ever made, few, if any, are as bad as the Chevy Vega. We can’t really think of anything nice to say about it.

Its aluminum engine was plagued by reliability issues. Poor cooling will lead to overheating and head gasket failure. As mentioned, the block is aluminum, but it may as well be hard cheese, as it’s extremely prone to warping and cracking.

Saab B205/B235

Saab used the B205 2.0-liter and B235 2.3-liter engines in models like the 9-3 and 9-5. The engines’ poor design can lead to various issues, including oil sludge build-up and timing chain failures. In addition, the service intervals were too long, which has led to many owners running their cars dry of oil.

As for the oil sludge build-up, it will cause poor lubrication and eventual engine failure. Timing chain failure is also a common issue and results in engine failure or expensive repairs.

Cadillac Northstar

Cadillac used its Northstar engine in a variety of models. The 4.6-liter V8 was the manufacturer’s first DOHC unit. It produced between 295 and 469 thoroughbred American stallions, and things were looking good for a while.

It didn’t take long before problems began popping up, though. Blown head gaskets are common, and curing the problem is expensive. Things eventually became so bad that mechanics started referring to the Northstar as the Deathstar.

Cadillac V8-6-4

Cadillac’s V8-6-4 engine was a 6.0-liter that featured a new engine management system that monitored the engine via an array of sensors. This allowed the engine to shut down cylinders under certain conditions, and in theory, the big V8 could be as fuel-efficient as a 6 or 4-cylinder unit.

The problem was that the system was based on ’70s technology and never worked properly. Owners would get their cars modified to function like a regular V8. In the end, the V8-6-4 damaged Cadillac’s reputation for years.

Yugo 1.1-Liter

Yugo is the butt of many car jokes and with good reason. The Yugo 55 had a carbureted 1.1-liter that produced an underwhelming 55-hp and was horribly unreliable.

For some reason, the engine required premium gas. It had an air pump-powered carburetor that was very inefficient, and the timing belt had to be replaced every 40,000 miles. In 1992, the EPA announced that every Yugo ever sold in the States failed to meet exhaust emissions.

Chrysler LH V6

Between 1998 and 2007, several popular Chrysler and Dodge cars were fitted with the LH engine. It was promising at first, but serious problems began to appear after a few years.

A poorly designed water pump causes coolant to leak into the crankcase, turning the oil into a sticky mess that blocks the oil passages. This sludge causes poor lubrication, and the engine eventually fails. Five class action suits were ultimately filed against Chrysler.

GM 3.6 High Feature Engine

Cadillac and Holden jointly developed the GM High Feature Engine for the 2004 model year, but it has since been modified and used in several configurations and displacements across GM’s brands.

The timing chain is the main issue here, as it stretches and throws off the timing. If it’s not sorted out, it will cause misfires, metal shavings will appear in the oil, and even catastrophic engine failure isn’t unheard of. Several other issues are also known to appear over time.

Nissan QR25DE

Nissan’s QR25DE engine is a 2.5-liter inline-4 unit, found under the hood of models such as the Altima and Sentra. The Altima is consistently listed as the worst Nissan model, so it’s no surprise that some of its issues are engine-related.

Due to poor engine design, the QR25DE engine consumes excessive oil and experiences timing chain failures. Either problem can lead to costly repairs.

BMW / PSA 1.6 Prince

Peugeot–Citroen and BMW jointly developed this engine, found in several French hot hatches and the second-generation Mini Cooper.

The timing system is the weak point here, as the timing chain loosens over time, causing it to rattle. If not dealt with, it can require expensive repairs. In addition, the turbocharged models are known to suffer from soot build-up, which causes loss of power.

Volkswagen 2.0 TSI

The Volkswagen 2.0-liter TSI engine is found under the hood of models like the Passat, Jetta, and Golf, and it’s suffers from timing chain tensioner failures and excessive oil consumption.

It’s another example of poor engine design leading to premature timing chain tensioner wear, and fixing it can be expensive. Excessive oil consumption is another well-documented problem that requires frequent top-ups or, if ignored, potential engine damage.

Jaguar V12

Jaguar introduced its V12 engine in the gorgeous E-Type, but strangely, it wasn’t much more powerful than the inline-six it replaced. Anyway, power isn’t the problem with the Jaguar V12 engine.

Its complex design makes it prone to overheating and oil leaks. It also enjoys drinking premium gasoline. Any car fitted with the Jag V12 will be expensive to own and maintain.

BMW N54

BMW’s N54 engine is famously fitted in performance models like the E90 335i and the E82 135i. Initially, it was a hit among tuners, but it was soon discovered that it was plagued by various reliability issues.

Its turbochargers are known to fail, often prematurely. That’s also the case with the high-pressure fuel pump. Cars that haven’t been serviced regularly or have lived a hard life are more prone to these issues, but even meticulously cared-for cars have been known to develop problems.

Toyota 3VZ-FE

Even Toyota, the masters of reliability, have messed up at some point. Its 3.0-liter 3VZ-FE V6 engine, used in models like the Camry and 4Runner, is known for head gasket failures and poor performance, which has tarnished the brand’s reputation.

It suffers from frequent coolant leaks and overheating, which can result in expensive repairs. There are plenty of used Toyotas out there, so our tip is to just avoid models with the 3VZ-FE.

Chrysler 2.4 TigerShark

We must admit that Chrysler’s TigerShark engine has one of the coolest names in the industry. Other than that, it’s a pretty dreadful unit that led to an $8 million class action settlement in 2022.

The original TigerShark engine was developed in the early 2000s, and when Fiat bought Chrysler, they decided to add Fiat’s MultiAir2 variable valve timing head to it. It resulted in excessive oil consumption, poor performance, mediocre fuel economy, higher emissions, and quite a few wrecked engines.

Oldsmobile Diesel

Oldsmobile really didn’t have a clue what they were doing when they decided to convert its 350 V8 gasoline engine to run on diesel. It was inefficient, underpowered, loud, unreliable, and spewed out black smoke.

Did we mention that it was also very unreliable? The head bolts would stretch because of the high compression, which caused blown head gaskets and engine failure. This engine single-handedly ruined the market for diesels in the States. It also led to a class action lawsuit and the creation of the Lemon Law.

Mazda Miller Cycle V6

Mazda is the master of unusual engines, with the Wankel rotary being the prime example. While the rotary isn’t particularly reliable, it’s better than the Miller Cycle V6 unit.

Most 4-stroke engines use the Otto cycle, but Mazda built a supercharged 2.5-liter V6 that used the Miller cycle, which basically means that compression happens in two stages by leaving the intake valve open longer. It suffered from excessive oil consumption and failing superchargers. There’s a reason why you won’t find many of these today.