I purchased this car 6 months ago with 79,000 miles on it. It currently has 85,000 , I got the oil changed just 2-3 months ago and tires rotated. Just recently within the last week my gas mileage has started dropping. I was getting between 40 to high 30s per gallon in town, but now I’m averaging in the 20s and it’s revving hard coming from a stop it’s having to go high into the red on power to get to speed, and is showing around 6-10 mpg when starting from a stop and engine is running hard. Even after getting to 30-40 mph when I left off gas to drift and apply again to get back to speed it revs high into the red to come back up 5-10 mph. The hybrid battery seems to be fine, cause when looking at the volts from the 12v battery when idling reads at 11.7 then jumps to 13.8 when I turn the car on. I’m wondering would the 12 volt battery drop the gas mileage by that much?
Ready mode is the important thing, not an undefined "idle". If its 11.7 at Ready it is extremely low but that's likely measured without Ready. Generally 13.8v at Ready just says your 12v battery is charged but says little about your hv battery which could be weak. Codes? Low power at initial acceleration is a classic low hv battery indication as is low mpg. I would have a retailer or dealer do a 12v load test since its a quick and often free test. There are isolated cases of a severely ruined 12v battery dragging excessive power from the hv battery and the 11.7v when off is low, but I would expect higher charging voltages over 14v.
that's a lot for the 12v, but it is worth checking. the hybrid battery may be going south, but you can't do anything until it throws a code, unless you want to test it an consider reconditioning. you likely have some clogging in the egr circuit, and i would get on that asap, before the head gasket blows
By idle I meant when you hit the power button twice without foot on break to get to the screen where you can see the vehicle signals.
