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I have noticed a significant improvement in the performance of my Dmax when using the GM winter grille cover. Recently during a routine dealer service I had been told by a GM shop foreman not to use the cover when the outside temperature is warmer than -18 degC (0 degF). Even so I have continued to use the cover since the engine temp does not seem to go higher than what I have observed during warmer weather and as a point of fact the engine temp is running apx. 10-15deg warmer than without and the same weather conditions. Also I have a noticeable increase in fuel economy with the cover on rather than not and that is with outside temps even approaching +10degC.

The basic question is . . . . should I heed the advice of the shop foreman or rather use the cover as I see fit (as I monitor the engine temps)?

Diesels I have always been told run better HOT hence the reason GM gives you a winter cover with the purchase of the truck.
 

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the foreman is high.:rolleyes:

run it below 32* unless for some reason you see high temps.

I run my grill cover only all winter, no bumper cover, have had it on in 45* weather and just started to see some peaky temps when stopped at lights.
 

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I run mine anytime it is cool enough that the engine doesn't run hot. Much improved fuel milage and much warmer in the truck. When it is real cold I cover the holes in the bumper with duct tape because it is difficult to get the lower cover on when it is cold.
 

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Mine's been on for weeks and is actually frozen in place.

When its in the 20's or below, mine goes on.
 

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You are correct,use it till the engine temperature starts running higher than normal.
 

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Went to have my starter replaced at 30k, and the service manager didn't want to replace it but he did. Then he started talking about having my winter cover on, and he said Michigan doesn't get cold enough for it to be on and told me to take it off. Then he showed me a paper from the General not to use it above (0 degF). He made me feel like it caused my starter to go bad.
 

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Ramblinrodney;1562355; said:
Went to have my starter replaced at 30k, and the service manager didn't want to replace it but he did. Then he started talking about having my winter cover on, and he said Michigan doesn't get cold enough for it to be on and told me to take it off. Then he showed me a paper from the General not to use it above (0 degF). He made me feel like it caused my starter to go bad.
Whatever...

Does he drive one? No, probably not.

When its in the teens, my temp barely reaches 170. This went for my 04 LLY as well. The winter cover keeps the engine running at around 190 or so. They make it for a reason. It came with it so I'm using it.
 

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Not only does it help your engine reach and maintain EFFICIENT operating temperature, but it also "slicks" the front of the truck aerodynamically and will save you fuel at highway speeds. The truck, being designed for towing, has an extremely efficient cooling system, and if not being worked in cool ambient temps will keep the engine too cool to run efficiently. I've run mine in changing conditions up to 50 degrees (F) air temp with no problems at all.
 

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Keep it on until it gets to the point of getting hot then take it off. Around 32 I would say is the "magic number" not to go above. -10 last night and mine still did ok w/o the "bumper cover" just the grille cover.
 

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Idle_Chatter;1562378; said:
Not only does it help your engine reach and maintain EFFICIENT operating temperature, but it also "slicks" the front of the truck aerodynamically and will save you fuel at highway speeds. The truck, being designed for towing, has an extremely efficient cooling system, and if not being worked in cool ambient temps will keep the engine too cool to run efficiently. I've run mine in changing conditions up to 50 degrees (F) air temp with no problems at all.
:exactly:
 

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and that whole "Michigan bit"...

guess what? there are only certian states of dealer delivery you can even RPO the winter cover set on the order.

Michigan is one of them.

ask your "foreman" why that is? :rolleyes:

GM seems to think it gets cold enough there! ;)
 

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I live in Iowa...mine did not come with a winter cover...
 

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Fountain Power;1563545; said:
I live in Iowa...mine did not come with a winter cover...
Check your window sticker to see if it was ordered with the truck. Sometimes the dealer forget to give them to you or the come up missing. If you ask your sales rep some times they will come up with one.
 

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thejdman04;1563440; said:
Keep it on until it gets to the point of getting hot then take it off. Around 32 I would say is the "magic number" not to go above. -10 last night and mine still did ok w/o the "bumper cover" just the grille cover.

:exactly: X2
 

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My truck in Northern Illinois was ordered with a cover. When covering the grill do you fully cover it or leave a corner undone and tucked to the inside? I thought I read on hear last year that people were throwing codes with the cover on.
 

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I cover the grill only. I tryed the bumper cover once on my 02. You can't pay me enough to put the bumper cover on again. I like the 06/07 tranny cooler design because the tranny always ran kinda warm on the older styles.
 

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tbalt;1563658; said:
My truck in Northern Illinois was ordered with a cover. When covering the grill do you fully cover it or leave a corner undone and tucked to the inside? I thought I read on hear last year that people were throwing codes with the cover on.

Fully install the grill cover. You'll have no problems unless you use it in fairly warm weather. I remove mine when its above 32 F. It is simple to put on/off. If your towing, you probably should leave the cover off. These trucks need the cover to help maintain their ideal operating temperature. Fuel economy is better when the engine is at normal operating temps too. I don't use the bumper cover either.....I think you'll find most people detest them because they are a pain to install and allow crud to collect under them prematurely rusting your bumper. My 2 cents.
 

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LT3Diesel;1563703; said:
Fully install the grill cover. You'll have no problems unless you use it in fairly warm weather. I remove mine when its above 32 F. It is simple to put on/off. If your towing you probably should leave the cover off.

Thanks
 

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I have had mine on at 65* and my truck never went above 200 where it normally runs the fan didn't kick on. If the highs are below 40* I would put mine on.
 

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Mine didn`t come with the cover but a fellow from Oklahoma parted with his and its been in place on mine all month. Trans temp comes up to normal 150 instead of just barly moving off the lowest mark. Engine stays around 200 and the fan hasn`t kicked on yet. Truck seems to go better with everything all warmed up and still getting 18mpg. running with both on in the mid 30`s no worries. Any warmer though and the bumber cover will come off till we start seeing 50`s again . going below 0 f this weekend l8r bb
 
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