If you’re reading this, you’re probably considering purchasing (or currently own) a General Motors vehicle with the 1.4 and 1.5-liter versions of the Small Gasoline Engine (SGE) engine family. If you want to learn more about the issue of melting and cracking cylinder heads, keep reading.
What is GM’s Small Gasoline Engine (SGE)? GM’s Small Gasoline Engine, also known as the Microtec engine, is an engine family developed by General Motors since 2013 and available in displacements ranging from 1.0 to 1.5-liters found in various GM vehicles worldwide. The SGE can utilize either multi-port or direct injection and be naturally aspirated or turbocharged. In this article, I want to specifically discuss the 1.4L and 1.5L turbocharged variants over their propensity to melt or crack cylinder heads. These versions are found in Chevrolet Cruze, and Malibu models, among others. What is the issue? The SGE hasn’t had a stellar track record for reliability since its debut, but among the most significant problems plaguing it is the melting and cracking of cylinder heads. Besides a design oversight with the piston itself (which uses cast for better fuel economy rather than forged), other factors are causing this failure, including Low-Speed Preignition (LSPI) and fuel and engine oil quality. LSPI happens when fuel detonates prematurely before the spark-triggered ignition occurs, creating enormous additional stress on the piston around areas not designed to handle excess stress, such as the sides of the piston. Over time, the piston’s head will crack or melt, accelerating a host of other issues occurring such as misfiring, premature wear or failure of piston ring and oil control ring, cylinder wall scoring, and more. With modern engines today, automakers have ramped up fuel injection pressure and compression ratios, which can significantly speed up the rate of internal wear, especially if components cannot handle such extreme pressures. If a piston’s head cracks, it will need to be replaced. If other issues such as cylinder wall scoring occur, the engine likely will need replacing depending on the severity of the scoring. What should I do if I own or want to buy a vehicle that has this engine? This is a problem that seems to primarily stem from the design of the cylinder itself, yet other factors contribute to its ultimate failure. With these engines, it is critical to use high-quality synthetic oil and change it frequently, preferably every 5,000 miles or less (with GM vehicles, be sure the oil you’re using satisfies Dexos specifications applicable to your specific model). Just as important as using quality oil, use quality gasoline. GM recommends 87 octane at a minimum. Because LSPI and engine knock are contributors to the failure of this engine’s cylinders, it may be wise to use 91 octane or higher for greater resistance. Using premium fuel may not be a complete fix to the problem, but it may mitigate it. I believe at one point I heard of there being an option from the dealership to retard the ignition timing to lower the internal stress the engine bears, but that likely wouldn’t fix the problem entirely, and it would also decrease performance and fuel economy. Should I buy a vehicle with this engine? I would not recommend this engine utilizing this specific piston design, as I have come across reports of piston cracking and melting with as little as 20,000 miles according to owner complaints. From my research, most cases relating to this problem appear to be between model years 2016 through 2017. As of now, I have not come across cases for model years 2018 or later exhibiting this flaw because GM supposedly improved the cylinder’s strength. I suppose, though, it’s always possible this issue may come back, especially if the ignition timing or compression ratios are changed. If your vehicle’s check engine light illuminates and shows a misfire code, you may have cracked or melted piston heads. I’ve seen videos on YouTube of owners and technicians taking off the oil cap and oil dipstick with the engine running and a large plume of white smoke, resembling a locomotive, escape. Despite this, the engine (amazingly) sounds normal, and if I were to walk by the car, I would never know the piston was cracked just by listening to the engine. If your heart is still set on a GM vehicle with this engine, I urge you to stay away from 2016 through 2017 model years, possibly even 2018, to be on the safer side. Note that by doing so, you may be avoiding the cracked cylinder head problem, but you may eventually experience other issues versions of this engine are known for, such as piston slap and premature turbocharger failure. Interestingly, I also discovered the 2.0L LTG EcoTec engine, optional over the 1.5L in the Malibu and used in other GM vehicles, also experiences this problem. I’m not sure if this issue affects all 2.0L’s (some with more or less horsepower than the Malibu), but I for sure recommend avoiding it in the Malibu and being very cautious when looking at other vehicles equipped with it. Opinion Due to strict emission regulations, automakers have become desperate to find a way to make their engines as fuel-efficient as possible, but this almost always results in lowered reliability due to the effect on the engine itself. Although the root cause of GM’s cracked piston head problem is the piston itself, other factors significantly contribute to its failure, including very high fuel injection pressure and compression ratios. And given the engine’s tiny displacement, it will experience even more stress than a larger engine. After selling my Oldsmobile (also a GM vehicle) before I bought my Hyundai, I looked at several Chevy and Buick models. I liked the redesigned Cruze and Malibu, but they are equipped with the affected engine. I’m grateful I found out about the cracked piston head problem early on. Additional resources Chevy Cruze Forum 1.5L Cracked Piston Head Thread Chevy Malibu Forum 2.0L Cracked Piston Head Thread Now you know the truth behind GM’s Small Gasoline Engine and its propensity to crack piston heads. I hope you have found this information informative and helpful. Still have questions or comments about this issue? I'd love to help. Feel free to leave them in the comments section below.
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