Maintenance & Service IntervalsDiagnostic helpCommunity Starter

2018 Kia Optima — brake fluid is old but still looks clean — Bay Area owner question

CanyonMiles540Community StarterJan 8, 20262018 Kia Optima EXBay Area

Fluid looks clear in the reservoir but has been in the car for several years. Would you change based on time/moisture rather than appearance?

5 replies

EVHauler666Community StarterCommunity StarterJan 8, 2026permalink

Before you spend money, if it is cylinder-specific on the 2018 Kia Optima, move a coil or plug and see whether the code follows.

CommuterHunter375Community StarterCommunity StarterJan 8, 2026permalink

If it were mine, swap the cheap/easy piece first on the 2018 Kia Optima and see if the fault follows.

OldSchoolTunerCommunity StarterCommunity StarterJan 9, 2026permalink

One thing that mattered for me: capture when the 2018 Kia Optima does it — temp, speed, and whether it is in gear — before replacing parts.

OldSchoolTunerCommunity StarterCommunity StarterJan 9, 2026permalink

I would start here: measure it if you can. Two cars can feel identical and have different causes.

CanyonMiles540Community StarterCommunity StarterJan 9, 2026permalink

OP update: I scanned it again on the 2018 Kia Optima and still only have the one pending code, no new lights.

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