Well with "Full Grill Block", MPG dropped significantly. Was getting better with 4 of 7 blocked. I think because I am in San Antonio, Tx...some grill block is OK but it is not cold enuff for a full grill block. The intercooler still needs a cool supply of air. Also the CRD runs cool...168 degrees...and if the ECM detects higher temps it makes changes that cut back on power. For a smaller car this might work but for a 4300# SUV is actually hurts. I am back to just three slots open and testing.

The Three (3) middle slots are now open...the second on the passenger side leads to the air box...

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Founder of L.O.S.T.
2006 CRD Sport
Mods: GDE Hot Tune w/ 364#@2000rpm/Air Box /3" Str8 Exhaust/ASFIR Alum Skids/245-75R-16 Cooper STT PRO/OME LIFT w/Clevis & 4 Spring Isos/AirTabs/Rigid 10" S2 LED/4xGuard Ctr Matrix Bumper
Drag Strip:Reac=.1078_60ft=2.224_1/8=10.39@64.8mph_1/4+16.46@80.8mph

I don't close off till below 32 degrees and we have been in the teens steady and below zero last night.
Still averaging over 25 mpg with winter diesel and 50/50 city/highway and temp gauge still one needle
width off of dead center, so up here with full block, there is still plenty of cool air being drawn in around
the inserts from Lund, and under the bumper. With the gas air box mod I cover them all, but only when
it is below 32. Center comes open when daytime temps are above, and with the Lund inserts, they are on
and off without any tools.

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2005 Silver Limited CRD 53,000 miles
GDE EcoTune / Trans tune
PML Differential Cover/Crankcase Mod
Tal & Hadas Grill Guard/TransGo Shift Kit
V-6 AirBox/Lunar Boost & EGT
Lund Cold Weather Grill Insert
OEM updated Filter Head, Cummins Lift Pump

Darby,

Thanks for noticing that blocking off the whole grille doesn't work too well.
I was thinking of doing it too. I imagine conditions here in N. FL are similar
to yours in TX.
Here is what mine look like...

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U.S. Army Retired