The vast majority of Optimas will be sold with a 1.7-litre diesel engine that punts out 139bhp, and it’s a lot better than in other Kia and Hyundai products we’ve tried, because it’s more flexible. Peak pull arrives at 1750rpm, but there’s a decent slice on tap below that, so you never find yourself in the doldrums unexpectedly. There’s very little point in revving the engine to its limits, because you don’t ultimately go much faster, so it’s best to adopt a relaxed driving style and let the engine’s low-down grunt do the bulk of the work. The engine can sound a little gruff at times, but the volume is kept low and you don’t feel many vibrations coming through the steering wheel and pedals. And, while wind- and road-noise aren’t suppressed to class-leading levels, they’re isolated well enough to give an acceptable level of high-speed calm.
A six-speed manual gearbox comes as standard, which is entirely inoffensive to use, but many buyers may be tempted by the optional seven-speed twin-clutch transmission. Yes, it swaps cogs smoothly once you're up and running, but it can be a little hard to drive smoothly at low speed, while its hesitancy to react when pulling out of junctions or onto roundabouts can lead to the odd heart-stopping moment.
The Optima is also available as a PHEV plug-in hybrid model, which uses a 2.0-litre petrol engine and an electric motor to produce 202bhp while drastically boosting efficiency. Trouble is, it does it in an irritating way when you’re not running on electric power alone (which you can do for a maximum of 33 miles, up to speeds of 75mph). Apply any sort of meaningful pressure to the throttle pedal, or come up against an incline, and the automatic gearbox immediately kicks down and works the petrol engine to its limits. The transmission also has a tendency to search around for the correct ratio, and seldom finds it at the first time of asking. The volume and the harshness of the noise makes driving the car too wearing for too much of the time. It’s not like you’re repaid with strong pace, either; it’s reasonable, but the car feels nowhere near as strong or as flexible as the output suggests.