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2013 Toyota Prius — hybrid fuel economy dropped with no warning light — Houston / owner question

DetailScout4Community StarterFeb 7, 20262013 Toyota Prius ThreeHouston
2013 Toyota Prius Three, about 65,000 miles. Same commute and driver, but average MPG is down noticeably. Tires are properly inflated. What hybrid-specific data would you inspect before blaming the high-voltage battery? If I figure it out I will update the thread.
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6 replies

HighwayDaily626Community StarterCommunity StarterFeb 7, 2026permalink
I'd want a measurement, not a hunch. Capture voltage while the 2013 Toyota Prius is actually failing — after it restarts you've lost the clue. Don't erase codes until someone who can help has seen them. This is from a 2013 Toyota Prius in Houston with 65,000 miles. If they can't show the line item, I assume it's hiding. I refuse to clear codes until someone else sees them.
WrenchEnthusiast541Community StarterCommunity StarterFeb 8, 2026permalink
Asking because it changes the advice: Loaded-suspension checks on the 2013 Toyota Prius catch play that a wheels-hanging inspection misses. You'll know quickly if you're on the wrong tree. No need to make it theatrical. I refuse to clear codes until someone else sees them.
MarketDIYer793Community StarterCommunity StarterFeb 8, 2026permalink
Start with the test that can prove you wrong. A pressure test beats staring at a dry driveway if the 2013 Toyota Prius is losing coolant with no puddle. That's the branch I'd chase this week. When does it actually happen? I've seen both outcomes, which is why I'd test instead of assume. If the story changes I'll post the new data.
DetailScout4Community StarterCommunity StarterFeb 8, 2026permalink
Cleared nothing. I want service to see the alert on the 2013 Toyota Prius first. That's my plan before I call anyone.
MarketDIYer793Community StarterCommunity StarterFeb 9, 2026permalink
If it were in my driveway, get a real battery/charging test on the 2013 Toyota Prius, not just resting voltage, before blaming a module. That's the branch I'd chase this week. When does it actually happen? Not trying to scare you — just skip the expensive first guess. Wrote this up on my lunch break.
RoadTripDetailerCommunity StarterCommunity StarterFeb 9, 2026permalink
Agree — and I'd add this: A pressure test beats staring at a dry driveway if the 2013 Toyota Prius is losing coolant with no puddle. You'll know quickly if you're on the wrong tree. On “hybrid fuel economy dropped with no warning,” that was the fork that mattered for me. Run the total, not the monthly, before you commit. Cold start is when I can actually reproduce it.
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