Should the Regal 1.5T use 92 or 95 octane gasoline?
3 Answers
According to the official car manual recommendation, the Regal 1.5T should use 95 octane gasoline. In addition to checking the suitable gasoline grade in the car manual, you can also check the fuel tank cap, where the recommended grade is usually indicated. Generally, the gasoline grade can also be determined based on the engine's compression ratio. Cars with an engine compression ratio between 8.6-9.9 should use 92 octane gasoline, while those with a compression ratio between 10.0-11.5 should use 95 octane gasoline. However, with the application of new technologies, the gasoline grade cannot be solely determined by the compression ratio. High compression ratio engines can also be tuned to use lower octane gasoline because, besides the compression ratio, other factors such as ignition timing, turbocharging technology, and Atkinson cycle technology also play a role. Generally, the higher the gasoline grade, the higher the octane number and the better the anti-knock performance. 92 octane gasoline contains 92% isooctane and 8% n-heptane, while 95 octane gasoline contains 95% isooctane and 5% n-heptane. If the Regal 1.5T occasionally uses the wrong gasoline grade, simply switch back to the correct grade after consumption. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles recommended to use lower octane gasoline, using higher octane gasoline will not cause damage, but the increase in octane number will alter the fuel's ignition point, leading to delayed combustion in the engine. This means both the engine's power output and thermal efficiency will decrease, resulting in poorer performance. For vehicles recommended to use higher octane gasoline, using lower octane gasoline can cause engine knocking. Due to the significantly lower octane number, the gasoline's ignition point decreases, causing premature ignition during the compression stroke. If combustion occurs before the spark plug fires during the compression stroke, resistance will arise during the upward stroke. This resistance makes the engine run very unstably. If the knocking is imperceptible, it only increases noise without obvious damage to the engine. However, noticeable knocking indicates severe engine conditions, affecting not only driving stability but also causing abnormal wear on pistons and cylinders, and in severe cases, cylinder scoring.
When I drove the Buick Regal 1.5T before, I specifically researched fuel options. The manufacturer's manual clearly states that 92-octane gasoline is acceptable, so you can rest assured—I used 92 daily. Although 95-octane is more expensive, it offers better anti-knock performance. I occasionally used 95 for long trips or during hot summers, and the engine noise did seem quieter. However, the actual power improvement is negligible, and using 92 long-term is perfectly fine. The key is to stick to a reliable gas station and avoid low-quality fuel from sketchy places, as that can seriously damage the engine. The money saved from using 92 for city commuting is enough for two basic maintenance services—it’s a smart trade-off.
After driving for over a decade, I've noticed many Regal 1.5T owners struggle with fuel grade choices. Here's the conclusion: 92 works fine, but 95 is better. 92 octane is economical and fully meets the engine's basic requirements, but turbocharged engines operate at higher temperatures where 95 octane better prevents knocking. If you frequently carry heavy loads on highways or enjoy aggressive acceleration, 95 is recommended. For gentle daily driving, 92 is perfectly adequate. The fuel cap states 'Use 92 octane or higher unleaded gasoline' - follow this guideline. Remember not to mix fuel grades; sticking to one type long-term is most engine-friendly.
