"我曾就机油使用寿命专门咨询过美孚,答复是所有的美孚机油(普通,半合成与全合成)不开罐的贮藏寿命是十年,开罐后为一年."
I believe they are talking about the oil not in use but just sits then for a year.
"全合成机油的优点是低温流动性和高温抗氧化性能"
This is why fully synthestic oil lasts longer since it resists heat-induced oxidation better.
"也就是说在可以选择 也可以不选择使用合成机油时,使用合成机油在换油间隔上没有区别。"
Don't understand the logic based on the above statements.