EngineDiagnostic helpCommunity Starter

2018 Kia Optima — oil level drops between services with no puddle

EVTraveler220Community StarterApr 19, 20262018 Kia Optima EXRaleigh

I started measuring the oil level every few hundred miles and it is definitely falling between changes. There is no obvious puddle and I do not notice smoke. How would you document and diagnose this instead of guessing?

4 replies

TorqueGeekCommunity StarterCommunity StarterApr 19, 2026permalink

Start with the test that can prove you wrong. Loaded-suspension checks on the 2018 Kia Optima catch play that a wheels-hanging inspection misses. If the cheap test changes it, stop and reassess. This is from a 2018 Kia Optima in Raleigh. No need to make it theatrical. Your commute and mine probably aren't the same, but the test still applies. I'll poke at it this weekend.

TrailGarage119Community StarterCommunity StarterApr 20, 2026permalink

Quick add on that: Swap the cheap/easy piece first on the 2018 Kia Optima and see if the fault moves. You'll know quickly if you're on the wrong tree. This is from a 2018 Kia Optima in Raleigh. A shop burned me once by skipping that step. Heat soak after errands is the other window.

TrailGarage119Community StarterCommunity StarterApr 20, 2026permalink

Log the conditions before you spend. Get a real battery/charging test on the 2018 Kia Optima, not just resting voltage, before blaming a module. If the cheap test changes it, stop and reassess. On “oil level drops between services with no,” that was the fork that mattered for me. Learned this the expensive way on a previous car. Parking it somewhere I can hear it better next time.

PistonHunterCommunity StarterCommunity StarterApr 22, 2026permalink

I'd push back a little: Swap the cheap/easy piece first on the 2018 Kia Optima and see if the fault moves. You'll know quickly if you're on the wrong tree. If they can't show the line item, I assume it's hiding. Happens in gear, not in park, for what that's worth.

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