Break In Period

[Adster]

I was just wondering about other people's break in period on their trucks in regards to gas mileage and power. I've had my 2008 Sierra Crew Cab w/ 5.3 E85 since the beginning of July and have been getting terrible gas mileage and power until just recently on my last 1000km trip at approx. the 6500km mark. I took it relatively easy on the truck for the first 1000km but other than that it's gone right to work, towing a 5500lb load a couple times for 500km and hauling between 800-1100lb load a few times and I generally drive no slower than 120kph even with the load. Getting 14mpg avg @ 135kph empty and about 10-11mpg avg towing.

 

The last trip I hauled 1000lb load 500km and avg about 15mpg @ 130kph(80mph) and returned at 135kph getting about 17mpg empty. The power was noticeably better in terms of down shifts (or lack of) on steep hills. So I am quite pleased now that it is starting to open up and do better.

 

My dad has an 07 Avalanche (GMT900) with the same engine and he didn't notice it getting better mileage until about 15,000km.

 

My question is what has everyone else noticed was the cross over point where their truck started getting better mileage and power? I kind of have a suspicion that the truck have it pre-programmed in for a certain amount of revolutions/km's whatever to take it very easy on the engine regardless of the demands placed on it until a certain limit and then it gradually opens it up to full performance once each preset break in limit is reached. Does that sound about right?

 

My dad was a mechanic for 20 years and he simply does not believe in break in periods at all and is as hard on the truck at 10km as he is at 100,000km's. Saying it's run in at the factory before you even get it. What's everyone else's thoughts? Do you take it easy for a long time and baby it, or do you treat it like a truck that's built for hard work right out of the gate's?

 

Oh, and I have a 2008 GMC Sierra Crew Cab 4x4 Z71 SLE.

 

Better give a pic of mine (just from a cell phone, not very good quality):

 

[tnord]

for racing engines, you'll get the most power from running them hard right from the get-go. i had a total of about 3min on mine before i put it on the track. the rings need high cylinder pressures that occur at WOT and high RPM to seat the best. i don't know how this affects longevity.