The Hidden Truth Behind Automakers' Engine Reliability and the Straight 6 Suppression

Automakers have long been criticized for producing engines that seem less reliable than those from previous decades. At the same time, the straight 6 engine, once a staple of smooth and powerful performance, has been noticeably absent from many modern vehicles. This post explores why some automakers might make engines that don’t last as long as enthusiasts expect and why the straight 6 engine has been deliberately sidelined in favor of other configurations.

Classic straight 6 engine block in a workshop

Why Engine Reliability Has Declined

Increasing Complexity and Cost Pressures

Modern engines are packed with technology designed to meet strict emissions and fuel economy standards. While these innovations improve environmental performance, they also add complexity. More parts mean more potential points of failure. For example, turbochargers, direct fuel injection, and variable valve timing systems require precise calibration and maintenance. When these systems fail, repairs can be expensive and complicated.

Automakers face intense pressure to reduce production costs and meet regulatory requirements. This often leads to compromises in materials and design choices. Some manufacturers use cheaper components or reduce the thickness of engine parts to save weight and cost. These decisions can reduce the engine’s lifespan.

Planned Obsolescence and Market Strategy

There is a theory that some automakers intentionally design engines with shorter lifespans to encourage repeat purchases. While this is controversial, evidence suggests that planned obsolescence plays a role in some industries. Engines that require costly repairs or replacements after a certain mileage can push consumers toward buying new vehicles.

This strategy aligns with the business model of many automakers who rely on continuous sales rather than long-term durability. It also explains why some engines from the 1980s and 1990s are still running strong, while newer engines face reliability issues earlier.

Emissions Regulations and Engine Tuning

Stricter emissions regulations have forced automakers to tune engines for lower emissions, sometimes at the expense of durability. Running engines leaner or with higher combustion pressures can increase wear and tear. For example, direct injection engines are prone to carbon buildup on intake valves, which can lead to performance loss and engine damage over time.

Manufacturers often prioritize meeting emissions targets over long-term reliability, especially since warranty periods cover only a limited time. This trade-off affects the overall lifespan of modern engines.

The Straight 6 Engine and Its Advantages

Smoothness and Balance

The straight 6 engine is known for its natural mechanical balance. Unlike V6 or inline 4 engines, the straight 6 has evenly spaced firing intervals and balanced forces, resulting in less vibration and smoother operation. This makes it ideal for luxury cars and performance vehicles where refinement is key.

Power Delivery and Simplicity

Straight 6 engines offer a good balance of power and simplicity. Their long crankshaft allows for smooth torque delivery across a wide RPM range. They also tend to be easier to maintain due to their straightforward design, with all cylinders in a single row.

Historical Popularity

Many classic cars from BMW, Mercedes-Benz, and Jaguar featured straight 6 engines. These engines earned a reputation for reliability and performance. Enthusiasts often praise the sound and feel of a well-tuned straight 6.

Vintage car engine bay with a straight 6 engine

Why Automakers Suppressed the Straight 6 Engine

Packaging Constraints

One major reason automakers moved away from the straight 6 is packaging. The engine’s length makes it difficult to fit into modern front-wheel-drive cars or vehicles with tight engine bays. Compact V6 and inline 4 engines are easier to place transversely, saving space and allowing for more cabin room.

Cost and Manufacturing Efficiency

Building a straight 6 engine can be more expensive due to its size and the need for a longer crankshaft and camshaft. Automakers prefer modular engine families that share parts across different models. Inline 4 and V6 engines fit better into these modular platforms, reducing production costs.

Marketing and Trends

Market trends have pushed automakers toward smaller, turbocharged engines with fewer cylinders. These engines meet fuel economy and emissions standards more easily. The straight 6, being larger and heavier, does not fit this trend well.

Some manufacturers have revived the straight 6 in recent years, such as BMW with its new turbocharged inline 6 engines. However, these are often reserved for premium models rather than mass-market cars.

Modern turbocharged straight 6 engine in a luxury car

Examples of Engine Reliability and Straight 6 Usage

Toyota’s Inline 4 and V6 Engines

Toyota’s engines are known for reliability, but the company has largely avoided straight 6 engines in favor of inline 4 and V6 designs. Their focus on proven, simple designs with strong manufacturing quality has kept their engines durable.

BMW’s Commitment to the Straight 6

BMW has maintained the straight 6 as a core part of its lineup, especially in models like the 3 Series and 5 Series. Their modern turbocharged straight 6 engines combine smoothness with power and meet emissions standards. This shows that with investment and engineering focus, the straight 6 can still thrive.

American Automakers and V8 Dominance

In the US, V8 engines have historically dominated performance and luxury segments. The straight 6 was largely replaced by V8s and smaller V6s for packaging and power reasons. This shift also reflects consumer preferences and manufacturing strategies.

What This Means for Consumers

Understanding why some engines are less reliable and why the straight 6 engine is rare helps consumers make informed choices. If you value smoothness and durability, looking for vehicles with well-maintained straight 6 engines or proven inline 4 and V6 engines is wise.

When buying a new car, consider the trade-offs between emissions, performance, and reliability. Researching specific engine models and their track records can save money and frustration.

Final Thoughts

Automakers face many challenges balancing cost, regulations, and consumer demands. These pressures have led to engines that may not last as long as older designs and the decline of the straight 6 engine in many cars. However, the straight 6 remains a symbol of smooth, reliable power where it is still used.