I was reading some past threads on breaking in diesels. One mentioned the increasing gas mileage as the engine wears.

Can anyone put a number/timeline on this? What have been your experiences?

I am looking for a truck under 10,000 miles used so from what I gather I will still be in the "break-in" period (the engine will be run in a good way by then but the engine won't be done breaking in).

Steve

 

Just for reference, this is the thread I was reading on breaking in engines:
https://www.ford-trucks.com/forums/5...revisited.html

And more specifically, this is the post that raised my question:

Steve

 

Got just over 8000 on my 08 F450 and it started getting a little better .went from 12 to 15 on highway but thats watching what i was doing speed and RPMs.

 

My last two diesel trucks, S L O W L Y increased in mpg until I hit just over 20k. Then it jumped about 1mpg. I got another 1 mpg increase when I turned 35k. The mileage then seems to level out from then on.

 

What are your latest mileage averages now? I see you are in an 05 350 with a 6.0l.

Steve

 

Combined hwy and city driving is 17.5mpg. Straight hwy at 65-70 mph is a solid 20mpg. Pulling a 14k fifthwheel at 65mph 11.5-12mpg. Pulling mountain passes with fifthwheel (with some 6% grades) 9.5 mpg.

Have thought of doing some exhaust and tuner mods, but the truck runs so well, that I don't want to mess with it. The truck is still running the original flash. I've had two notices for reflash, but I'm not going to have it done.

 

Thanks for the info. That is actually what I get in my 1/2 ton silverado now... which is surprising. I am right around 20 highway on the high end. As much as I hate to say it, the last time I calculated my mileage in the city it was 14, just me no load commuting to school back in Dayton (climbing in/out of the Miami Valley on 48 and stop/go traffic). The next chance I get I will run a mileage check and see what I am getting combined city/highway. This will be interesting!

I didn't make any attempts to know what my mileage was yanking a trailer to Chicago a couple months ago.. I kinda wish I did now, just for comparison. After I dropped that off I got just over 16mpg the next day with my truck loaded, no trailer.

The more I read and the more I talk to people the more interesting this gets. I was just at the local truck accessories store today and I had a nice long chat with the owner. He said the same thing everyone here has - the newer trucks have so many emissions equipment that they can't get good mileage no matter what is done (keeping things legal). His 06 duramax is getting over 20mpg lifted with big tires (around 35's if I remember right), and 17 pulling 10k lbs, after his upgrades. Hmm.

Steve

 

Currently my 6.0 will get 17-19 Hwy and 11-13 in town when not towing which is about the same as when it was new. I've noticed little to no break-in improvement

As far as I've heard, the newer higher reving engines, tighter tolerances, etc just don't seem to require as much of a break-in. My 7.3 and Chevy 6.5 both had a noticible improvement after break-in.