When we cruise for long periods of time, usually about 78 mph at 3000rpm, we get a warning to add a quart of oil. This happens when we drive to Florida once or twice a year. I added a quart after the last trip and it happened again this trip but I only put in about 1/2 a quart. Now whenever we get up to cruising speed on our local expressway it asks for oil again. It doesn't come on whenever my wife is just cruising around town at low speeds.

The reason I'm concerned is because we don't have a dipstick to check if it is being overfilled and, since we park it in a garage, we would know if anything is leaking. I don't know why we would use up 2 quarts of synthetic oil when we haven't even come close to the mileage of a standard oil change.
Is this normal? We have a 2004 C320 with pretty low mileage. 90% of my wife's trips are 5 miles or less at speeds under 50mph

 

Wow, I never would have expected that. The only other cars I've ever had that used oil like that were clunkers that needed new rings Anyway, I've added oil now so thank you for the reply.

It's a 6 cylinder engine not the 8.