Replaced my Nexen with Michelin CrossClimate2 tires last Fall on my 2016 Soul Plus (17" tires) at 60k miles. [Including the '16 Plus, I've had other 4 Souls, from 2 Base (16" tires) models through 2 Exclaim (18") models.] The Michelin are the best tires I've used on my Souls; great ride, quiet running, excellent traction in dry, wet, and snow/ice conditions! About 2-3 better mpg after 8 months of driving. In the end, your right foot more than anything determines your gas mileage and tire tread wear.Yesterday I completed a trip to New Haven CT from the Reading PA area where I live. The Kia’s computer said 38.5 mpg. My measured mpg was 35.3. Considering this is a brick on wheels, I’m not complaining. In fact, I’m pretty happy with my mileage. I’ve had mine since one week pre-Covid. it has about 14300 miles on it. The measured fuel economy for those mile is 30.8 mpg combined. This Kia replaces a 2011 Forte EX which had 63500 miles on it. It averaged about 33 mpg on the highway and overall mileage was 28.9. I like my Soul EX.
I found that the original Nexen tires were garbage on wet, slushy or snow covered streets . They were down right hazardous when it came to stopping on snow, slush, or ice so I replaced them with Nokian WR4G all weather tires which have been excellent. I figure I may be paying a slight mpg penalty, but the added safety factor is worth it .
P.S. I've found the 1.6L engine in the Base, with the higher gearing of the 6-spd A/T, consistently gets about 6-8mpg better than the 2.0L engine, regardless of model year, 2016 and earlier.