Mourn with me. Cadillac – Cadillac! – no longer sells a single car powered by a V-8 engine. Or such will be the case in about two months, when 2014 fades to 2015. Come Jan. 1, all new Cadillac cars will be powered by fours or sixes. Some will be turbocharged. But none will larger than 3.6 liters. The last of the V-8 Caddys – the (very) limited production CTS-V sedan/wagon – is being retired. There appears to be a replacement on deck for 2016, but the continued politically viability of V-8 engines within the system (so to speak) is...