2019 Audi S4 — coolant is old by age but mileage is low

Intermittent stuff lies if you only catch it once. Write temp, speed, and in-gear vs coast when the 2019 Audi S4 does it — then decide on parts. Save the big job until that test fails. On “coolant is old by age but mileage,” that was the fork that mattered for me. Learned this the expensive way on a previous car. Climate here is different, so treat that as a local data point. No warning lights, which is why I'm documenting it.

I wouldn't throw parts yet. Move a coil or plug on the 2019 Audi S4 if it's cylinder-specific and see whether the code follows. Don't erase codes until someone who can help has seen them. This is from a 2019 Audi S4 in Cleveland. I'd want that in writing, not as a promise. Your commute and mine probably aren't the same, but the test still applies. I refuse to clear codes until someone else sees them.

Update: the cheap test changed the symptom, so I'm not throwing parts yet. If this is nothing, great. I want that in data.

This is usually cheaper to test than to guess. Two 2019 Audi S4s can feel identical and have different causes, so measure before you copy someone else's repair. Save the big job until that test fails. If they can't show the line item, I assume it's hiding. Doing the boring step first on purpose.