The overhead is usually out by 1 to 5 MPG. I have never come close to the overhead when I hand calculate
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2008 Ram 3500 CTD 6.7/68RE/3:73 LSD (It was built right, nothing fell off)
Previous Rams: 1990 CC Dually, 1994 RC LB, 1995 CC SB, 1998 QC Dually,
2000 QC Dually, 2001 QC Off Road, 2003 QC Dually, 2005 QC Dually
REAL TRUCKS DON'T HAVE SPARK PLUGS