I recently paid to have the coolant in my car flushed while they were replacing a thermostat.

My mechanic said that I should keep an eye on the coolant level and top it up with WATER.

I was always told this was a bad idea and Mercedes explicitly state not to use water.

I’ve called the shop that carried out the work, they say they are super busy and booked out until late next week.

Am I being stupid, or should I push for them to top it up with actual coolant? It’s a two second job, surely!

TL;DR Coolant tank is slightly low, mechanic says to top it up with water instead of coolant.