What was surprising, to me, is that our Kia Sorento plug-in hybrid (PHEV) struggled a bit to keep up with the demand. To clarify, we pushed the Sorento PHEV up that steep grade hard. Not only did my wife have the cruise control set to over 70 MPH going up this long, steep grade, we had about 600 pounds of cargo, the temperatures were about 90 degrees Farenheight, the AC was blasting, nearly every USB port was actively charging devices, and we had a car fridge running off the 12 volt. Even though we turned on Sport Mode a few miles before we started up the Grapevine, we lost ⅓ of the stored energy in the battery by the time we reached the top (we had 12 miles of range when we started up the grade, and only 8 miles when we reached the highest point). But let me be crystal clear on this: the Kia Sorento PHEV did not struggle to maintain speed in these conditions at all. Nor did it overheat or show any other signs of “distress”. So it may not be honest to say it truly struggled. But had I not have had the foresight to keep about ⅓ of the battery “on tap”, I don’t know if the PHEV would have been able to maintain the speed my wife had dialed into the cruise control (78 MPH at the start of the climb, soon dialed down to 72 MPH once the slope increased). I intend to test this on the way home, but I expect that had she turned off the cruise control, and simply let the vehicle slow down a few MPH while going up the grade, she would not have lost 4 miles of EV range. I won’t head up that steep pass with a depleted battery mind you (because I don’t want to find myself in the situation where I can’t maintain the speed limit at least - not that I know that would happen), but I suspect that a challenging mountain pass such as the Grapevine pushed the limits of the PHEV powertrain, at least a little. I intend to test how the HEV mode handles the pass on the way home, with at least 6 miles of range in the battery as reserve when I start the ascent, without switching into Sport Mode. If the Sorento PHEV might struggle to maintain speed or deplete the battery faster without switching on Sport Mode, I want to know this. I’ll likely do this without the cruise control on going home though because I know that it will rev the engine more than necessary to keep the set speed, instead of just slowing down a few MPH.
We are 1,348 miles into our trip after reaching our destination. To get here we have consumed approximately 36.2 gallons of gas and 58 kWh of electricity (accounting for losses from charging). That comes out to roughly 37.2 MPG, combined, for that distance. That is roughly the same MPG figures I got when I made a similar trip years ago in my old 2007 Honda Fit (a much smaller and lighter vehicle than our Sorento PHEV). I only had to pay for about 3.5 kWh that I have used so far on this trip as I charged at family or friend’s houses or at places that offered free charging otherwise, like our hotel, which had several chargers though half the J-1772 chargers were inoperable. This made me glad I brought my Tesla destination charger adapter so I could charge up using those instead. All told, the 58 kWh cost me $1.43. The gasoline came out to roughly $177 for the trip down (gas is expensive on the west coast!), which is not bad, all things considered.
A final note on this outbound trip; I now know without a doubt that Sport Mode is less efficient (in most circumstances) because, if nothing else, it keeps the gas engine running when Eco + HEV mode would not. For example, when I was in stop and go traffic with several miles of range on the battery, Sport Mode would keep the engine running for longer while coasting or braking, also clearly idling it when I didn’t need any power from the gas engine for several seconds at a time. Also creeping along at very slow speeds Sport Mode would crank up the gas engine when there was clearly no need for it. So even if everything else is equal, Sport Mode will get worse efficiency when the engine is under light to no load. That may only result in a small difference in efficiency, but it absolutely confirms in my mind that Sport Mode is best reserved for strenuous driving conditions like going up mountain passes or towing, if you prioritize efficiency.
Images courtesy of Justin Hart.
Justin Hart has owned and driven electric vehicles for over 15 years, including a first generation Nissan LEAF, second generation Chevy Volt, Tesla Model 3, an electric bicycle and most recently a Kia Sorento PHEV. He is also an avid SUP rider, poet, photographer and wine lover. He enjoys taking long EV and PHEV road trips to beautiful and serene places with the people he loves. Follow Justin on https://www.torquenews.com/kia for regular electric and hybrid news coverage.