02 Civic SiR. I just noticed the coolant is about an inch below the "low" mark on the reservoir. There are no operational problems, runs normally, doesn't overheat. Is this low enough to have caused any damage?

I don't have any extra on hand, but it's booked into the shop tomorrow morning for an unrelated maintenance item, so I'll ask them to top it up. The manual is very specific about using a particular Honda brand coolant. This is just an independent shop (no Honda dealer in town), so I have no idea if they'll have it in stock.

1 Answer 1


If you are talking about the overflow reservoir being an inch under the "fill" line, there really shouldn't be any issue. Just keep an eye on it and make sure you keep up with it ... if it continues to lose coolant, then you might have room to worry. For instance, if you are seeing there is an inch of coolant in the reservoir missing every month, then your concern needs to raise a bit. If it's an inch every week, then there's probably a bigger issue. If this is a one time thing, not much to worry about ... it can happen. Just pay a little extra attention to it and make sure.

As for the brand of coolant, yes, you should be using Honda blue coolant, but it doesn't have to be branded by Honda. There are aftermarket versions of the coolant which is formulated not to cause your engine any issue, but it doesn't come from Honda (and won't fetch the Honda prices, either).

  • Thank you. I just got this car a few weeks ago, so I can't say whether there's a pattern of coolant loss. I'll top it up and keep an eye on it. Commented Nov 11, 2018 at 22:44

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