I did a Diesel Purge cleaning today and while doing so I did a rough test of the fuel usage at idle.

I connected the fuel lines and poured one 16oz can of DP into my clear bottle. Then I purged the system with the hand primer until the pre-filter was full and fuel was coming out the return line back into the bottle. Then I marked the fuel level on the bottle with a Sharpie. Next I poured in the 2nd can of DP into the bottle and started the engine. It took approx 30 minutes for the fuel level to drop back to the sharpie mark on the bottle. 32 by my watch, but given the accuracy of the sharpie line, lets say 30mins.

So 128 oz per gallon, 30 mins per 16 oz, that's 4 hours per gallon. My 1985 300TD idles at 950rpm, so for those of you whose cars idle slower should use less fuel at idle.

-Tad

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1995 G320
2003 C230 Kompressor Coupe
2005 ML500
2007 ML350