2003 Mercedes Benz CL500 • V8 2WD Automatic • 27,000 miles

I have a 2003 CL500, which I used to get a combined fuel consumption of 15 – 16 l / 100KM, for me with the A/C on almost all times I think this is very acceptable. I went for oil service; I honestly don’t know what the oil used before because I bought this car less than 3 months ago, I used Liqui Moly W5 30 which is approved by Mercedes Benz to be used, I changed the oil and the air filters and thats it, nothing more has been done to the car, after that the car fuel consumption becomes 17.5 – 18.5 l / 100KM, need to know what possibly happened. By the way my car is well maintained and did only 43K on the clock. Many thanks in advance.
August 14, 2011.

Check to make sure no vacuum hoses were accidently knocked off or damaged. Make sure no sensors were left disconnected.