2017 prius... 123k miles. Recently the mpg dropped almost 10mpg. Only things i have had done were replacing sparkplugs with the correct toyota ones and draining and refilling both coolants. No warning lights. Alignment is not perfect... could that be responsible? Any tips on what to check?
There a lot of possibilities but I had the same problem last year and I started replacing suspension parts to find out what was causing it. Concluded that coil springs were the problem.
And this was before the mpg drop? "I have had done" infers by someone else; if so: who was that? I'd also suspect bogus plugs, just because. The 'someone else" purchased them, or you? To be candid, I'm not sure what the mpg impact would be from bogus plugs, but worth exploring. Nothing else, undisclosed? Say new tires?
