Fuel Efficiency and Emissions Are Hurting Engine Reliability

Key Points

• Smaller, more powerful and fuel-efficient engines don’t seem to have great long term reliability. 
• Engine recalls from major automakers such as GM, Toyota and Honda have cost billions of dollars. 
• Moves to make engines more efficient while maintaining power, such as thinner engine oil, seem to be the culprit. 

Modern car engine technology is probably the best it’s ever been, with engines getting smaller and more efficient while maintaining output levels of bigger power plants. Unfortunately, this progress comes with a trade-off: reliability. Vehicle recalls have been high for the last few years; according to the National Highway Traffic Safety Administration, there were over 29 million vehicles recalled in 2024, with 2025 recall levels shaping up to be as much or slightly more. A major focus of the recalls are engines: Per Automotive News, there are currently over 5 million engines from five major automakers that are either under recall or facing more serious investigations. 

Related: Toyota Again Tops Consumer Reports Annual Auto Reliability Survey

Fuel Efficiency Seems to Be Hurting Long-Term Reliability

• Takeaway: The technology that has allowed engines to become smaller, more efficient and make horsepower similar to larger engines seems to be one of the main reasons so many engines are being recalled.

Stricter fuel-economy standards backed automakers into a wall. How were they supposed to deliver engines that are efficient while maintaining the power that many customers demand? Automakers responded by turbocharging engines or more commonly implementing direct fuel injection. The results were engines that could deliver hybrid-rivaling fuel economy, such as Hyundai’s naturally aspirated 2.5-liter four-cylinder that delivers over 30 mpg combined in the Palisade; small three- and four-cylinder engines can also deliver impressive fuel economy and make power comparable to V-6 and V-8 engines from 20 and 30 years ago, such as Ford’s 315-hp EcoBoost four-cylinder for the Mustang and Toyota’s high-performance 300-hp, turbo three-cylinder that powers the GR Corolla. 

While these engines may be the stuff of automotive engineers’ dreams, that power and efficiency comes at the cost of reliability. Simply put, these modern engines are too high-strung and running too hot. Automotive News spoke with industry experts who said that the power and high temperatures these engines are running at are putting considerable stress on critical engine components. Compounding things is the use of thinner engine oil, which also aids in increasing fuel economy and horsepower. 

This thin engine oil is also affecting engines that have historically had great reliability. In April, GM issued a recall for nearly 600,000 vehicles powered by its 6.2-liter V-8 in the U.S., including the Chevrolet Silverado 1500 pickup truck and Cadillac Escalade SUV, for engine failure. NHTSA also opened an investigation for another 286,000 vehicles in late October. GM has said it expects 3% of these engines to fail dealer diagnostic tests. Those vehicles that have their engines fail the test will receive new engines; engines that pass will receive thicker engine oil. 

What Automakers Are Saying

• Takeaway: Automakers aren’t saying much about these recalls for obvious reasons, but they remain committed to making things right for those owners who have been affected by them. 

Recalls, especially ones surrounding powertrains, aren’t great topics for automakers. We reached out to GM, Honda and Toyota to see how they’re handling things. GM didn’t respond, though we’ll update this post if it gets back to us. Toyota spokesperson Jacob Brown sent a statement saying where owners could find information regarding the recalls and briefly described the problems going on with the recalled V-6 engines:

“There is a possibility that certain machining debris may not have been cleared from the engine when it was produced,” he said. “In the involved vehicles, this can lead to potential engine knocking, engine rough running, engine no-start and/or a loss of motive power. A loss of motive power while driving at higher speeds can increase the risk of a crash.”

Honda spokesperson Jake Berg more or less said the same thing, stating the automaker is committed to owner safety and detailing where owners can go to find resources for recall help and information:

“In November 2023, American Honda recalled approximately 250,000 vehicles across multiple models for a recognized connecting rod defect, and the majority of vehicles included in this recall have already been repaired.”

Engine Recalls Are a Pricey, Time-Consuming Headache

• Takeaway: Recalls are costing automakers billions, hurting dealer profits and inconveniencing consumers.

Millions of engines under recall are spreading the hurt around to automakers, consumers and dealerships, with automakers set to spend hundreds of millions of dollars on engine-related recalls for 2025. Per Automotive News, current major engine recalls include:

• Ford: Over 700,000 Ford engines are under recall for failures that could ultimately result in engine fires. It’s not known how much these recalls will cost Ford.
• Honda: Nearly a quarter of a million V-6 engines from Honda have been recalled for engine failure, and another 1.4 million engines were added to the recall after a NHTSA investigation. It’s also not known how much the recall will cost the automaker.
• Hyundai: Over 3 million of Hyundai’s Theta II, Gamma and Nu engine lines have been recalled, affecting models going back over a decade. A slew of lawsuits, settlements and fines means that Hyundai could eventually pay out over $5 billion because of the recall.
• Stellantis: Over 120,000 2023-25 Jeeps have been recalled over engine failures. The recall could cost the automaker $500 million.
• Toyota: Some 229,000 of Toyota’s twin-turbo hybrid V-6 engines are under recall due to debris in the engine block that can cause engine failure. The automaker is expected to pay over $1 billion after everything is said and done.

If an engine failure results in the automaker approving a full replacement, it is a time-consuming affair that ultimately disrupts customer lives. For instance, replacement of Toyota’s hybrid V-6 can take anywhere from 13-21 hours, pulling experienced dealer techs away from other services.  

What can a consumer do? Just be careful and do your due diligence when buying a car. If you’re in the market for one of these vehicles (or any vehicle, for that matter) with an engine recall, make sure to request a vehicle history report to see whether or not a recall fix has been performed on the car. Or you can have an independent mechanic check the vehicle out for you, something that can usually be negotiated on when buying a vehicle. In the end, it’s the owner of the car that’s affected most. Be it a commuter who needs their vehicle to get to work or a contractor who needs their truck for their livelihood, engine unreliability has repercussions that can affect everyone.

Read More News on Fuel Efficiency and Reliability:

• What Is Good Gas Mileage?
• Fuel-Economy Standards May Get Rolled Back to 34.5 MPG by 2031
• What Are the Most Reliable Cars and Brands?
• Are Electric Cars Better for the Environment?
• What Are the Most Fuel-Efficient Cars?

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