I think it would be possible to answer a question like this if sufficient data was collected about various vehicles:
I am quite comfortable asking the question, but where should I ask it?:
The main site would be ideal...
... since it can reward contributors with reputation. But then the data will be fragmented across multiple answers and the Q&A format breaks a little since there isn't really a right or preferred answer.
Could question community-wiki-fication be a solution here? It would be disappointing that CW questions don't reward contributors with reputation, but that is the only drawback I can see.
Meta is a possible venue to ask this question...
... but it isn't a question about the site. 'Nuff said.
And then there's chat.
But chat is volatile and will soon be forgotten, and this question will remain relevant and answerable for a long time because there are literally tens of thousands of different makes and models that could serve as unique datum points in the quest to discover this rule of thumb.
I'm leaning towards a CW-style question on the main site, but want to know what others think of this idea first.