The 2019 Infiniti QX50 is fresh start with striking exterior styling, a more luxurious presentation, Level 2 semi-autonomous driving and a first-of-its-kind engine with variable compression. There are a lot of moving parts to the redesigned QX50, the brand’s midsize five-passenger SUV crossover. Its new 2.0-liter VC-Turbo four-cylinder engine is getting much attention in advertising and in road-test evaluations, but not all of it is progressive. Infiniti says the engine’s variable compression ratio technology is...