Was averaging 51mpg without even trying. Now I'm down, quite suddenly, to 46.5. Only significant change in driving habits or conditions: Spent about 3 months doing more hwy driving than usual... but mileage did not change much. Then took a road trip from LA to San Francisco... that's when I started seeing a bigger difference. Dealer has been nagging me to clean the fuel injectors. I keep saying no. Could he be right?
Is your 12V week. Below 12v after sitting over night. Does it really drop under load{lights on} Maybe working hard to keep 12v up? H
Any change in how the car glides? IOW, do you sense it slows quicker? This would bring low tire psi or a dragging brake into play, or alignment/balance issues. Barring that, it could be a dieing 12V as HaroldW noted, or it could be time to change plugs, clean the MAF &/or throttle body, etc. And yes, fuel injectors are a possibility, too. Does the engine run now at times it has always been off before? Again, this would point to bad 12V (much less likely the HV pack from all I've read). Check your tire pressure. Check your 12V voltage. Try to classify the issue per the above. If she glides like a champ still, and if your 12V tests ok and everything seems normal except mpg, then you are into new plugs, cleanings, etc. A recent oil change may have been with the wrong viscosity or too much oil. At this point too much unknown.
