True, on roads, tracks...
True, on roads, tracks, frozen lakes and in remote deserts I often test cars whose tanks have been filled by the manufacturers. But I also spend time driving around in a wide variety of gas-guzzling and frugal models which run on fuel I"ve paid for. It"s impossible to estimate how much I"ve personally spent over the decades. But the last thing I"m prepared to do is beat myself up over the fact. And although it"s entirely up to you, my humble advice is that you shouldn"t feel bad either.