Can fully synthetic engine oil be changed once a year?
2 Answers
Fully synthetic engine oil can be changed once a year, while conventional mineral oil should be replaced every 5,000 kilometers or six months; semi-synthetic oil should be replaced approximately every 7,500 kilometers or around eight months. However, in reality, whether the engine oil needs to be changed depends on many objective factors, such as the usual driving environment, personal driving habits, and the quality of the oil itself. Strictly speaking, fully synthetic engine oil refers to high-quality oil products made from 100% PAO (polyalphaolefin) or artificially synthesized esters, labeled with the "synthetic" mark on the packaging. In simpler terms, engine oils blended using Group IV or Group V base oils without the addition of mineral oil for dilution can be considered fully synthetic engine oil.
I used to drive a car that always used full synthetic oil, and it felt great for five or six years. Every time I went for maintenance, I’d ask the mechanic if I could change it once a year. He’d always say synthetic oil is indeed durable and resistant to aging, but it depends on how you drive. If I only drove 8,000 kilometers a year, all on highways, then it’d be fine. But since I mostly drive in the city with stop-and-go traffic and short trips, the engine doesn’t get up to temperature, and the oil is more prone to carbon buildup and contamination. Over time, it can actually harm the engine. Once, I tried to save money and stretched it to thirteen months, but later I noticed the car had lost power. A checkup revealed the oil had thickened, and after changing it, the filter had to be cleaned too. So now I recommend following the manual—most car manufacturers suggest changing the oil once a year or every 10,000 kilometers, whichever comes first. Don’t rigidly stick to a year. If you don’t drive much on long trips, checking the oil quality after eight months is a safer bet. Get into the habit of checking the dipstick regularly—if it’s black or sticky, deal with it sooner. Oh, and high summer temperatures can accelerate oil aging, so parking in a garage helps, but don’t overlook it.
