High fuel consumption?

It sounds like you're describing a normal operation. I'm accustomed to miles per gallon, but the idea is the same. Usually there's two different fuel use ratings. You're seeing the instantaneous rating that updates a couple of times per second, as you drive. I'll let you worry about converting to kilometers per liter, if you care to, but for me, my mileage will go from roughly five to eight miles per gallon when accelerating up to speed, (which is rotten), to between 18 to 40 miles per gallon during cruising at highway speed and coasting. Coasting for just a few seconds at highway speed can get the reading as high as 99 miles per gallon. That's as high as it can read.

None of these numbers are realistic because they all refer to the many variables at that instant. It's more of a novelty, and it lets you see what driving habits you can change to improve fuel usage.

Every car I've ever seen so far with a fuel use gauge includes a different setting you can switch to that shows average fuel usage. For my truck, that hangs around 18 miles per gallon, which is much better than trucks got 20 years ago, but with careful driving on long trips, I've gotten the average up to 22.4 miles per gallon. Conditions have to be just right, and on mildly hilly roads, I can't use the cruise control. Cruise control demands the vehicle hold its speed, and that means accelerating and down-shifting when going up hills. Coasting down hills begins too late to take full advantage of those hills. I had the best mileage by following semi trucks that naturally slow down going up hill.

The average fuel usage is what you want to watch. It looks like my truck calculates that average over the previous ten miles, but other people have told me my minivan's readings are an average over longer stretches, like as much as fifty miles.

You will have a menu choice that lets you reset the average fuel usage back to 0.0 kilometers per liter. That's nice if you want to see how well you did on a long trip, for example. There's no resetting the instantaneous reading. That just shows what it is at any instant.

It's still a good idea to measure the distance you drive between three or four fill-ups, then calculate your kilometers per liter to see how accurate your average dash readings are.

As a point of interest, when I idle the truck engine to warm it up, my average miles per gallon drops by one tenth for every minute it idles. Same is true when sitting at red lights. It can take five to ten miles at highway speed before that average reading goes back up a tenth of a mile. To say that a different way, it's really easy to get the average to drop a lot, but it takes a lot of gradual acceleration and careful planning to get the average mileage to go back up just a little.

Also, it sounds to me like your gauge can read the number of liters used per 100 kilometers, OR, ... You're mixing up those numbers. There is, in fact, a different number that does go way up during coasting, but I shouldn't even mention it as it will just unnecessarily confuse the issue. That is the volume of fuel being pumped out of the gas tank. That volume does go up very high during coasting, but 99 percent of that gas goes right back into the tank through a return hose. The percentage of that volume that actually goes into the engine drops way down during coasting. I've never seen that fuel volume displayed on any instrument cluster, and they never would as it has no relevance to any driving styles or conditions.

Sounds like your car is working properly. Let me know if that helps or if you need more of my wondrous wisdom.