As long as your using top tier 87 the engine will run almost as well as on 91. I’ve done the same thing I switched to 91 for a month... mpg was just about the same and it was just as fun to drive running in 87 lol.I bought a 2020 JLUR Recon with 2.0L turbo (only engine available in Recon) and was concerned if driving on 87 octane would result in significantly lower performance than premium gasoline. I read the owner's manual and it stated that 87 octane can be used but for optimum performance, 91 octane is recommended. Therefore, I've maintained using regular gasoline after I drove off the dealer's lot for about 1.5 months. The 2.0L had great pep and the power was sufficient to make me smile. Curiously, I changed to 91 octane to see if there was any kind of marked change in performance. On premium gas, I noticed a TINY improvement in engine response and power. However, to be honest, if I had to make a comparison under a blind test evaluation, I probably could not tell you if I had been driving under regular or premium gasoline. Time and mileage will tell if using 87 octane results in a gradual decline in engine performance.