A major disadvantage of synthetic oils is they ____________.

The major disadvantage of synthetic oils primarily relates to the cost of their production. Synthetic oils are manufactured through a complex process that involves chemically altering petroleum base stocks or manufacturing entirely from chemical compounds. This requires advanced technology and precise refining processes, which contribute to higher costs compared to conventional mineral oils. Consequently, while synthetic oils offer superior properties such as better thermal stability, lower volatility, and improved protection against engine wear, the financial aspect can be a consideration for consumers and businesses when selecting engine oils.

In contrast, the other options revolve around specific performance characteristics that are generally not true for synthetic oils. For example, synthetic oils typically possess excellent temperature-related flow characteristics, allowing them to maintain viscosity across a range of temperatures. They are also designed to manage soot loading effectively and often exhibit improved oxygenating capabilities compared to traditional oils. These attributes emphasize the overall performance advantages of synthetic oils despite their higher production costs.