Should fuel mileage increase when engine is broken in?

[GOPDiesel]

I've read in the past that a new 6.0 engine, if properly broken in, will increase it's mpg. On these 6.0's, Is 10000-15000 miles the range where most people consider it "broken-in"? I'm not complaining about my current mileage, just wanting this question addressed by people with more knowledge than I.

Thanks, Pat

[luke0204]

Maybe a little, but don't get your hopes up. Mine has been doing the same 50 mile round trip to work for a year and a half and is maybe 1 mpg better than new with almost 48K on the ticker. My life to date average is about 15.5 mpg running from a low of 9 towing and almost 22 on the highway.

I traded the '04 in my sig with 25K on it and it was coming into its prime but the Edge and the 6spd definitely helped. It got about 1 mpg better than my '05.

[AllOutFirefighter13]

<font color="blue"> In theory ALL internal combustion engines on the road today will often (not always - my disclaimer) increase in fuel mileage at a certain mileage. The area of this mileage varies between vehicles because of the driving habits of the person in that vehicle. When freshly assembled, everything is "tight". This "tightness" takes more power, through the injection of more fuel, to keep it going down the road. Over time, this "tightness" loosens up, which takes a fraction of the load off the engine and it now takes less fuel to move the vehicle down the same road. I hope this helps!!

Later, </font>

[frobozz]

Yes, all Powerstrokes increase mileage potential up through about 10K miles. I saw it with our '97 F250HD owned from new, and i saw it with our '00 X owned from new. With the '03 6.0L truck I saw it but not nearly to the same extent. It started out getting worse mileage than the X (!!) and still does, even though it improved slightly with time.

Duncan

[tommymac]

I noticed a nice increase in fuel milage at about 32,000 miles. I switched to synthetic motor oil at about 16,000 miles so perhaps it delayed my break in time. In warmer weather, above 40 F., I was consistantly getting 15.5 to 17.5 mpg before, and now I am seeing 17.5 to 19.1. My driving hasn't changed and it is not due to a reflash. So in my case the milage did seem to go up after the engine "broke in".

[Runk]

at 80,000 miles now my '03 has been the same since new.
its been a pretty amazing truck, no real problems other than the state of calif making me take it to dealer to get it reflashed for emissions purposes.