What type of engine oil is suitable for the Buick GL8 25S?
3 Answers
The original factory engine oil is recommended for use in the Buick GL8 25S, with the oil specification being 5W-30. In terms of compatibility, the original factory oil is more suitable for the engine. However, depending on different needs, engine oils can offer additional benefits such as noise reduction, fuel efficiency, and improved performance. Therefore, you can also choose engine oils from brands like Mobil, Shell, and Castrol. The viscosity of engine oil changes with temperature, so special attention should be paid to its performance under both low and high temperatures. For example, in 5W-30, the first number indicates low-temperature fluidity, with 5W representing the ability to withstand temperatures as low as -30°C. The smaller this number, the better the low-temperature fluidity, resulting in smoother cold starts for the car. The second number represents the kinematic viscosity of the oil at 100°C. A higher number indicates better viscosity retention under high temperatures, which can also be understood as better lubrication performance under high-temperature conditions. The method for changing the engine oil in the Buick GL8 25S is as follows: Wait for the engine temperature to drop, allowing the oil to flow back into the oil pan. Use a wrench to loosen the oil drain plug and place an oil pan underneath to catch the old oil until it stops flowing. Start the engine and let it run for 30 seconds to allow the oil in the main oil passages to drain out. Use a specialized wrench to remove the oil filter. Apply some oil to the oil seal of the new oil filter and tighten it clockwise by hand. Add the new engine oil through the oil filler cap on the engine valve cover, typically filling about three-quarters of the oil container. Start the engine and let it run for 5 minutes, checking for any leaks around the oil drain plug and oil filter. If leaks are found, perform necessary repairs. After stopping the engine, pull out the oil dipstick to check that the oil level is within the standard range.
I've driven a Buick GL8 25S for three years and found that the manufacturer-recommended 5W-30 viscosity oil is the most suitable, as this all-season oil can start smoothly even at -20°C. Remember to choose a fully synthetic oil with dexos1 certification, especially if you frequently drive fully loaded on highways, as this oil offers strong high-temperature protection. I've personally used fully synthetic oils from Mobil and Shell, with maintenance intervals of around 8,000 kilometers each time, and the engine noise is noticeably quieter, with stable fuel consumption. A reminder: never use high-viscosity 40 oil, as it can clog the oil passages. Business vehicles like the GL8 are most afraid of breaking down midway, and proper maintenance can extend its lifespan by several years.
Having worked in an auto repair shop for over a decade, I've handled quite a few Buick models. For the GL8 25S with its 2.5L engine, you should use 5W-30 oil. If the viscosity is too low, lubrication will be insufficient; if it's too high, it'll increase fuel consumption and damage the engine. Full synthetic is of course the best, but semi-synthetic can also work in a pinch—the key is to have the dexos1 certification. I've seen too many car owners opt for cheap, off-brand oil, only to have the piston rings seized by sludge after 20,000 kilometers. I recommend checking the dipstick every 5,000 kilometers and changing the oil early if it appears black. Friends in the south can use this grade year-round, but those in the north need to pay extra attention to low-temperature fluidity in winter.
