Hello, I bought a used 2015 Prius C One a month ago. Initially I was thrilled with the car as any trip I made with my normal driving habits I was seeing 48+ mpg on the display even on relatively short trips. However about 2 weeks ago that suddenly stopped. For example a trip to my girlfriends house which is one i had made many times previously would always net me at least 46 mpg and that was with me being more aggressive on the pedal than i normally am. Now i'm getting around 38 mpg on that same trip. That trip is around 7 miles mostly on the highway. Shorter trips i get even worse mpg usually around 35 mpg. I haven't made any changes to anything whether it be my driving habits, the car, or anything that I could think of. I live in southern California so cold weather isnt really a factor here either. What I'm noticing is that I'll take a trip of around 7-10 miles from a cold start get bad mpg, stop the car and as long as I don't let the engine cool down again I will start to get the normal mpg i would get previous to this happening. I know when I'll start getting the good mpg again because the car will start with the 99.9 mpg on the display when I'm pulling out. Obviously at that point the car has gone through all the stages and is running efficiently. The problem I'm having is that when I first bought the car it didn't take that long to go through the stages and i could get good mpg. Another example i drove for 15 miles on the freeway yesterday again cold start and only got 38 mpg with a speed of 65-70 mph. I've tried checking everything else that I could think of like tire pressure, fluids, oil, etc. All seems fine to me. No error codes either. Anybody have any idea why this could be happening? I also checked my avg ev % usage and it was 17% does that seem on the low side or is that normal range?
Check the vent behind the drivers seat. I've seen this a lot where a bag or blanket is covering the vent hole.
Hey thanks for the replies. I'm not tracking miles manually but with my normal routine I need to fill up once every 14 days or so. Lately it's been once every 9 days or so. I don't have anything covering the vent behind the drivers side but I did pop off the plastic cover and there was A LOT of lint covering the vent grille. I cleaned it off and will report back to see if that helps.
imo, there are too many variables in short term mpg's on the dash. there's no substitute for tracking fill ups for finding mpg inconsistencies. easier than a wild goose chase to find what is wrong, when nothing may be wrong.
Agreed, though... a 33% drop isn't something that normally happens because of weather or driving conditions... usually. If he's sticking to the same route and driving mostly the same, I could see a drop of 10 mpgs at most. Going from 50 mpgs to 35 mpgs is a lot. Especially if it's not cold.
I figured out what was the problem. I had the car set to let in fresh air from the outside instead of recirculate cabin air so I'm guessing it was letting in cool air that kept the engine from warming up quickly. My mpg is back. Cleaning the lint out from the traction battery vent helped my eco score a lot too. Thanks for the help.
My guess is too much ethanol in the fuel he's purchasing. We have an issue with "Circle K" here in Indiana blending more than the normal 10%. Not all the time, but at least 3 times a year. My son and brother will both see cars pulling into the dealership in droves complaining of poor mileage, hard starts etc. I'd try a different brand of gasoline just as a test. My not be it, but it's possible.
A decent headwind can make that kind of difference, especially if it's compared against driving the same route in the opposite direction with an equivalent tailwind. And especially if it's driven at a high speed. Aerodynamic drag at high speeds makes a huge difference in fuel economy. Winds are often not at all obvious when you're driving except for their impact on economy. Whenever I see that "l/100km" display doing something I don't expect the first thing I do is look for flags or trees to see if there's a wind blowing.
50 mpg to 30 mpg because of wind speed and drag would be a terrible design... nobody would ever drive over 55 in the PC if that were the case.
Well, presumably the kind of person who would buy a Prius is the kind of person who places a value on fuel economy. If so, then they should be aware of how high speeds hurt that fuel economy. Air resistance increases as the square of the velocity, so it takes almost twice as much energy to plow through the air at 70mph as it does at 50mph. Which is exactly what you get if you drive at 50mph with a 20mph headwind. And it's very similar if you drive at 50mph with a 10mph headwind and compare it with the same drive in the opposite direction with a 10mph tailwind.
I've driven in some seriously adverse weather before and I've never seen 30mpgs. In the high 30s, sure... but not lower than 35.
Both wild guesses are totally without merit. A small percentage change in the ethanol content will have no noticeable impact on engine temperature. And the A/C settings have no impact on the engine temp either.......but cooling outside air this time of year DOES make the A/C work a LOT harder, which would make the engine warm up faster if any impact at all. The combination of the A/C setting plus the blocked vent probably accounts for your fuel mileage change.......but not because of engine temperatures.
