2015 Volkswagen Golf 2.0 liter diesel shows 5 total cars (out of 75 available). It looks like a database syncing error of some kind. Another way to see this is that is you look at the list of available engines to choose from and add up everything that shows up 40 cars seem to me missing.
Separately it would be nice to be able to sort/filter by fuel type in addition to engine type. since there are so many engine types the distinctions are meaningless.
Or show gas and diesels on the same histogram in different colors?