There are myriad reasons that mileage could decrease. I haven’t experienced this recently, but I have had random decreases in mileage before. Someone else in t

There are myriad reasons that mileage could decrease. I haven’t experienced this recently, but I have had random decreases in mileage before. Someone else in this thread mentioned having the gas tested and that could be possible but i would consider it unlikely. If you’ve checked spark and air filters, my next questions would be transmission and tires. Are your tires at the proper air pressure? Is your transmission slipping at all? Are your plugs fouled at all? You could ask a dealership to run a diagnostic, Toyota’s dealership technicians are actually pretty good.