Switched from bald General Altimax 175/65R15 to new Hankook Kinergy ST 185/65R15 and saw zero mileage decrease when factoring in the 2.1% size difference. I got them because they were nearly $100 cheaper after tax for a set versus comparable 175/65R15s (Came out to about $300 including installation thanks to combining a couple promos this summer). Plus I've run them on other cars for a while and they're fantastic tires. If you get the Kinergies make sure to get the STs not the GTs or PTs. The STs are the only Kinergy tires with high ratings.
I've done that, too. Original 175 tires lasted about 50k. With 175s at 80 indicated MPH I was actually doing 78mph according to GPS. After Biden tanked the economy the tires went from $60 a piece to $120. Purchased 185 Douglas from Walmart at $60 each. Now indicated 80 MPH equals 80 mph on GPS. Life is good. Drive on...
Your odometer will be off now. the car does know the more-or-less correct speed, but displays slightly more; the logic being to avoid drivers inadvertently speeding. You’ve “fixed” that.