Hi all; My 2010 Prius is pushing 90K miles now. I've noticed a sudden drop in MPG performance. I know cold weather is a factor, but even then, its pretty bad. I've gone from 65MPG on average to apx 45. I have a Scanguage and I've noticed that I'm having a hard time getting it to show "999999" when Gliding at highway speeds. I've never tuned it up. Never replace spark plugs, or changed the 12V battery. Also, a few months back I had to remove part of the bottom cover thingy right under the front grills, so my grill blocking for the winter is not as effective. I'm planning o change air filter, and battery by myself, and I'm trying to save some money. Any suggestions? Thanks!
I would suggest that the ICE is running overtime to keep the engine temperature up. I'm sure your are also aware that the cabin heater is probably being used overtime from driving around in frigid weather. This combined, can seriously put a big dent in your MPG. Also, what about tires? Have you switched to winter tires recently?
Location, say Florida vs Alaska, would help responders. New battery is worth a try. I'm thinking the removed underpanel is excessively cooling the engine bay (location?), and you could try some grill block: start with 50% of the lower grill (one pipe insulation tube, the 1.5" OD size).
Thanks for the info. Grills are 100% covered. I'm in NJ and its cold now. But I don't think the issue is temps cause I had this for the past 2 weeks and we had some pretty warm days. Also, the issue persists even when coolant temp is 195 degrees.
Unexplanined drop in MPGs is the first indication of an aging hybrid battery: How do I know if my hybrid battery is failing? - Hybrid Automotive
Absolutely. We also recommend on our site checking tire pressure first as well, as that can be a cause for decreased MPGs. If the basics those don't fix the issue, our $350 Battery Maintenance systems will do the trick for a whole lot less than waiting for the battery to fail and forking over $3k-$4k for a replacement.
