according to my mechanic, this is how fuel system cleaner should be used. 1 bottle of fuel system cleaner to a 1/4 tank of gas. Drive till it is almost empty. Then refill with gas or repeat as needed.

Alon

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'92 300CE - Sold
2004 C240 - 744 - C7 Wheels - Android Radio
2002 C320 - 816 - Sport Wagon - Sold
2006 E350 Wagon - 368 - Dead
2015 GL350 Bluetec - 197U