I think 7 bottles in an almost empty tank is way too much. The idea is to clean the injector pintels not ruin them. The cleaners in these bottles are meant to be mixed with fuel. The fuel actually provides a lubricating value.
I used Valvoline Max-Life in the 300E. It definitely improved the oil consumption: 1,000 miles per quart to about 2,200 miles. When I stop using it the oil consumption slowly increases. Search using: Haasman + Valvoline Max-Life.
I have often found that going slow, being methodical and analytical with determining what is wrong with a Mercedes pays off in more ways than one.
A lot of people spend a lot of money throwing parts at their cars to repair problems, when often simple adjustments after careful analysis is all that is needed. Some think that since it is a Mercede$ that the repairs $hould al$o co$t a lot .... not necessarily in my experience.
Follow the advice you just received: Check your mixture.
Keep us posted,
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)