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What 35 owners told NHTSA about the 2018 Toyota Prius Phev

These are the actual owner complaints behind this car’s reliability verdict, filed with the federal government, unedited. They’re unverified reports, not confirmed defects: read them as leads for your pre-purchase inspection, not a diagnosis.

All (35)Crash / fire / injury (5)Visibility & wipers (6)Lights (5)Speed control (4)Airbags (3)Body & structure (3)Brakes (3)Electrical system (2)Engine (2)Engine & cooling (2)Fuel system (2)

2 of 35 complaints match · Engine & cooling · clear filters

Jun 26, 2026Engine & cooling

The contact owns a 2018 Toyota Prius. The contact stated that while driving at an undisclosed speed, the engine constantly overheated. An unidentified warning light was flashing on the instrument panel. An independent mechanic inspected the vehicle and became aware that the coolant reservoir was empty. One month later, the same failure reoccurred. A second independent mechanic inspected the vehicle, and the coolant reservoir was empty. The vehicle was taken to a dealer. The dealer diagnosed the vehicle with a coolant leak into the head gasket. The dealer advisor referenced a customer satisfaction program as the cause of the failure; however, the vehicle was over the mileage limit for the program. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was 188,000.

NHTSA ODI 11746813

Mar 26, 2025Engine & coolingEngine

The contact owns a 2018 Toyota Prius. The contact stated while driving at an undisclosed speed, the check engine warning light illuminated. The vehicle was taken to the dealer where it was diagnosed with a failed heat exchanger, catalytic converter, and exhaust system. The contact was informed that the heat exchanger, the catalytic converter, and the exhaust system needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure but provided no assistance. The failure mileage was approximately 89,682.

NHTSA ODI 11650717

Working with the data? Download all 35 complaints as CSV · fetched from NHTSA July 20, 2026

How to use these: a complaint is one owner’s report, filed voluntarily and published unverified. Patterns matter more than any single story. If several owners describe the same failure at similar mileage, put that system at the top of your pre-purchase inspection list. Back to the full 2018 Toyota Prius Phev verdict →