I have noticed a decreasing mpg ever since I bought my 3rd generation prius a year ago. First , I was getting 52 mpg , then it dropped to about 42 , now I hardly get mire than 36 .My car is well cared for and I use regular gas (92 octane) and I use premium quality fully synthetic oil. I suspected the spark plugs were the issue , so I changed them with no avail. I have heard cleaning the maf sensor and the throttle plate may improve the mpg . Is this true ? Any suggestion is appreciated.
Check your 12 volt battery to see if it is over 12 volts after sitting all night. if it is 12.0 or lower get a new AGM battery with external venting and JIS posts. Be sure your wheel alignment is good and the tires have proper pressure Check your filters, air, Cabin Air, PVC valve, and oil... Check for dragging brakes with the tires off the ground. A bottle of fuel injector cleaner may help, I do not know how 'clean' Jordanian gas might be.
It's just the rears you can check thus, but yeah, good check. (Man it's hard to do a select-text-and-reply on a phone.)