My 1999 C280 has started consuming oil. It has just over 118,000 miles and up until this point never used any oil between changes. It now uses about 1 quart every 500-600 mile when on highway trips only. It doesn't consume oil during normal daily driving. I can drive it daily for a month of driving (about 1,000 miles) and it doesn't use any oil but when I take a trip and drive 4-5 hours at highway speed it uses the oil. What could be causing it to use oil during the highway driving?
Thanks,
Jim