Interested in Language
Wendy's father could teach Mama how to drive but he was always so busy at the Consulate and besides, their Mercedes-Benz was too new to learn on. They always quarrelled about it.
In my opinion, the meaning of the bolded fragment could be derived as follows:
Mercedes-Benz was very new. Mama could not learn on it. So we arrive at "Mercedes-Benz was too new for Mama to learn on" or not taking into account the doer, we obtain "Mercedes-Benz was too new to learn on".
In other words, Mercedes-Benz was too new to use to learn to drive.
Do you find my reasoning acceptable?
Yes, that is what it means. He feared that the new driver might get in an accident and did not want her to do so in his new car. Therefore, it was "too new" for her "to learn on."