DBTKDT Posted October 8, 2010 Report Share Posted October 8, 2010 All the sudden have a huge lose of mpg? I have a 2003 1500 HD with the LQ4 6.0. I always average 13.5 around town driving and could get 18 on the highway. That was with a 89 tune. I put in a 93 tune and bam the mpg went 4-5 mpg lower? I can not see it being cause by a tune? I don't want so mention the tune name but is a very well know tuner is always does top notch work! Does anyone have any idea where to ever start? I put back the 89 tune and will run that for a few weeks to see if it is something else? Looking for some thoughts and ideas. Thank you. Quote Link to comment Share on other sites More sharing options...
idahoBLKss Posted October 8, 2010 Report Share Posted October 8, 2010 if the only thing changed was the tune then it must be the tune... Quote Link to comment Share on other sites More sharing options...
blackbeast ss Posted October 8, 2010 Report Share Posted October 8, 2010 if the only thing changed was the tune then it must be the tune... tune!!!!! Quote Link to comment Share on other sites More sharing options...
BlueAKSSS Posted October 9, 2010 Report Share Posted October 9, 2010 No ones perfect maybe they just mistakenly tuned something wrong with your 93 octane tune? Is it throwing any codes? Quote Link to comment Share on other sites More sharing options...
f1ss Posted October 9, 2010 Report Share Posted October 9, 2010 I highly doubt this is it, but change your fuel filter or have you done it recently? Quote Link to comment Share on other sites More sharing options...
DBTKDT Posted October 9, 2010 Author Report Share Posted October 9, 2010 I highly doubt this is it, but change your fuel filter or have you done it recently? I changed that about three months back. What about O2's? I will see how it goes in the next week with the 89 tune back in? Thanks for the input guys. Quote Link to comment Share on other sites More sharing options...
8 UR HMI Posted October 11, 2010 Report Share Posted October 11, 2010 if this started when u swapped to a 93 octane tune, there is NOTHING REMOTELY POSSIBLE to effect the mph besides the tune. there isnt anything that could make it worse. ask ur tuner how much timing and spark, etc... u have when not under WOT. i guarantee ur probably a lot of spark and with upwards of 40* of timing in closed loop. just call ur tuner or have him live tune it. Quote Link to comment Share on other sites More sharing options...
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