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Hello , was just wondering if anyone had some info about breaking in the new 6.6 LML duramax. Also when should i do the first oil change and with what kind of oil and filter.
 

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Dear 2011LousDuramax,

I have read your post about your break in period for your new truck. On page 9-32 of your owner’s manual, you will find the break in information that you are seeking.

If you have further question, please don’t hesitate to contact me.

Michelle P., GM Customer Service
 

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I have a 2011 2500HD with the LML. Is there a break-in period where the computer will release so-to-speak more horsepower / better gas mileage and or let the engine run better after so many miles or are people just blowing smoke up my ---?
 

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From the manual:
Keep your speed at 55mph or less for the first 500 miles. Do not drive at a constant speed fast or slow. Do not make full throttle starts. Avoid downshifting to brake or slow the vehicle. Avoid hard stops for the first 200 miles. Do not tow a trailer during the brake in period. Do not exceed 50 mph for the first 500 miles of towing

From previous manuals – change the rear end fluid after 500 miles of towing

I kept mine under 60 for the first 500 miles.
Changed the engine oil and tranny fluid (TranSynd) prior to my first tow - had about 750 miles on the truck.
The first 100 miles of towing I kept it at 60 mph or less
100-600 miles kept it at 65 mph or less
After 600 miles of towing I changed the rear end fluid (I took the fluid, drain pan and gallon jug with me on the first tow)
When I returned home after my first tow (about 3000 miles on the truck) I changed the engine oil, tranny fluid (TranSynd) and tranny external filter. Greased the front end components.
Tranny fluid changes were made to convert to TES 295 synthetic fluid in the tranny
 

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From the manual:
Keep your speed at 55mph or less for the first 500 miles. Do not drive at a constant speed fast or slow. Do not make full throttle starts. Avoid downshifting to brake or slow the vehicle. Avoid hard stops for the first 200 miles. Do not tow a trailer during the brake in period. Do not exceed 50 mph for the first 500 miles of towing

From previous manuals – change the rear end fluid after 500 miles of towing

I kept mine under 60 for the first 500 miles.
Changed the engine oil and tranny fluid (TranSynd) prior to my first tow - had about 750 miles on the truck.
The first 100 miles of towing I kept it at 60 mph or less
100-600 miles kept it at 65 mph or less
After 600 miles of towing I changed the rear end fluid (I took the fluid, drain pan and gallon jug with me on the first tow)
When I returned home after my first tow (about 3000 miles on the truck) I changed the engine oil, tranny fluid (TranSynd) and tranny external filter. Greased the front end components.
Tranny fluid changes were made to convert to TES 295 synthetic fluid in the tranny


I find the guidance about keeping it under 55 MPH for the first 500 miles to be extreme. There must be tons of people who buy one some distant from home and have to drive them home, so what then, backroads for 500 miles, i dont think so.

Mine actually got broke in this way as i bought it locally, but jeez sounds extreme to me especially with today's technology.
 

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From the manual:
Keep your speed at 55mph or less for the first 500 miles. Do not drive at a constant speed fast or slow. Do not make full throttle starts. Avoid downshifting to brake or slow the vehicle. Avoid hard stops for the first 200 miles. Do not tow a trailer during the brake in period. Do not exceed 50 mph for the first 500 miles of towing

From previous manuals – change the rear end fluid after 500 miles of towing

I kept mine under 60 for the first 500 miles.
Changed the engine oil and tranny fluid (TranSynd) prior to my first tow - had about 750 miles on the truck.
The first 100 miles of towing I kept it at 60 mph or less
100-600 miles kept it at 65 mph or less
After 600 miles of towing I changed the rear end fluid (I took the fluid, drain pan and gallon jug with me on the first tow)
When I returned home after my first tow (about 3000 miles on the truck) I changed the engine oil, tranny fluid (TranSynd) and tranny external filter. Greased the front end components.
Tranny fluid changes were made to convert to TES 295 synthetic fluid in the tranny


I find the guidance about keeping it under 55 MPH for the first 500 miles to be extreme. There must be tons of people who buy one some distant from home and have to drive them home, so what then, backroads for 500 miles, i dont think so.

Mine actually got broke in this way as i bought it locally. We had actually planned to use it on a 2,000 mile road trip the day after i bought it but we ended up taking my wifes SUV due to space issues. Just sounds a little on the low side to me especially with today's technology.
 

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Mabe it makes the difference between lasting 1,000,000 miles and 1,500,000 miles:rolleyes:
 

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I give her hell everywhere I go! Tow'd a 20k trailer when it had 53 miles down to tx, then back empty...OOPS.
 

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All of these engines get tested after the engine assembly and then again when the trucks come off of assembly line to validate performance. If you think you were doing the truck a favor by being nice to it, a GM employee has already had it to the floor at the plant so no need to worry about being the first
 

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So is the 'break-in" 500 miles? My brother's 07 F250 had a break-in of 25,000 miles! No stupid mph restrictions but I know these motors have changed A LOT.

The main point is when can I start to notice better milage and power? Approximately?
 

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i had the same issue i purchased about 100km from home, drove her back at 100km/h on cruise, then some errands around town. I wont be burrying the pedal through the floor for a while yet, but 55mph for 500km? not happening.
 

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when i was test driving mine i eased through the dealership, turned onto the road and laid it to the floor. guess i missed the no full throttle part lol
 
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