Join Date: Mar 2017
Location: Saskatchewan, Canada
Likely need change your thermostats. Low engine temp will cause poor mileage. I changed mine on my lmm this summer when I did the hsp billet thermostat housing. Temp is 185-190 and mileage came back up.
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2008 Chevrolet CCSB Duramax - dpf delete, egr delete, pcv reroute, hsp cold air, hsp billet thermostat housing, hsp y-bridge cold side combo, banks ic pipe, efi tuned by ppei, FASS lift pump, dmax store downpipe, 5" mbrp exhaust, trans go jr, htt Promax 64, ppe shim kit, ppe ported rail fitting, bd drivers manifold, arp head studs, limitless diy kit built by me, limitless 1078 converter