A car owner who is too proactive about general maintenance introduces

Answer choice E is the best option here. If we focus strictly on the argument, it says that "Car owners should refrain from scheduling an appointment when the car appears free of any issue". For statements like this, I found it helpful to paraphrase the argument using short notation. To paraphrase into a conditional format I would write it as (if no issue -> no schedule appointment). The assumption that this argument is making is that automobile owners have the ability to detect when an issue is present. This is a big assumption that should immediately alert someone who is reading the argument.

Option A is irrelevant since our argument involves determining whether we should wait to schedule appointments until an issue is identified. The ability of mechanics is not what the argument is addressing.

Option B is irrelevant as the answer choice gives information regarding someone's ability to visit a mechanic, when the argument only makes a statement about whether someone should visit (whether someone is able to achieve this ideal is not really at issue. We care only if we learn more about whether someone should visit the mechanic provided they are able to)

Answer choice C is the second best option, although still flawed. Car owners may struggle to find the ideal time to schedule an appointment, but that doesn't really affect whether or not they should wait until there is an issue. Sure they might struggle, but so what? This doesn't weaken the argument that they "Should" wait to schedule an appointment. Just because someone struggles doesn't give us any insight into whether they "should or should not" perform the action.

Answer choice D I think missed the point of the argument. The argument is "Should we wait until there is an issue to schedule an appointment?" Whether or not larger auto chains have made their mechanics more effective is not actually relevant. For those who pick D, you might pick this option because you paraphrased the argument differently to something along the lines of "Owners are more effective at diagnosing issues than mechanics". In such a case, answer choice D could weaken by making the mechanics seem more competent, but even then it wouldn't be a strong weaken answer choice since we still don't have any knowledge regarding how effective automobile owners are.

Answer choice E directly addresses the gap in the argument regarding the ability of automobile owners to diagnose issues. By saying that owners are not able to and that mechanics are, we weaken the argument that owners should wait until they discover an issue since there could be undiscovered issues that go unchecked and cause more damage. This would strongly indicate that mechanics are more qualified to determine optimal check-up times, and would thus weaken the claim that car owners should wait to identify an issue before bringing the car in for maintenance.

I'd love to hear other people's thoughts on this question as well.