Diesel Break in before MPG improve

[bobfa]

I have a new F250 PS 6.7 with trailer package 4 x 4 3.55 axle and 20" wheels. My current trailer is 21 Microlite and I am guessing I have it loaded to about 4100 lbs. I can get 20 - 21 on highway or 15 city no problem. On the highway with the trailer my only trip I gauged 12.5 mpg. Funny, I read of people pulling rigs 2 and 3 times heavier with same truck and some say they get 15 and even higher 17, 18??? (I can't believe some of the numbers). I know my gas TV only got 8-10 mpg taking it real easy at that. So do I have something to look forward to in improvement as I get more miles on the diesel? I only have 1800 miles and did not tow till I had 1200 miles on it. I plan to buy a 5er in a few years, so maybe the trailer gross weight makes no difference??

[Muddypaws]

We towed a 10,000# Arctic Fox with a 2001 F250 and got decent mileage. When we upgraded to a heavier & taller fifth wheel it got better, probably because of better aerodynamics.

Once you get up to cruising speed the aerodynamics become more important than weight.

I've only had my F250 for 12 years. It's not quite broken in yet.

[JudyH]

We have a 2011 Ford F350 with that 6.7 diesel, and we pull a big 5er. Our mileage varies, but not pulling we regularly get 17 mpg. Pulling we have gotten as much as 10+. But factor in higher speeds or wind and the mpg goes down. It is much better than our 7.3 did. And Way better than the old 460. We are at about 35000 miles so far. Good luck.

[caissiel]

You are right my 15k 5th wheel tows better then the previous 12k 5th wheel and much better then a 7k TT.
it's in the shape of the trailer and the distance from the cab and height does not mather. My present unit is 30 inches higher.

The tires and air pressure in them makes a lot of difference. The TT I refer to had 65psi and previous 5th wheel had 60psi. My present unit has 7k axles with 110psi tires. I know now why semis are so great on fuel with 18 or more wheels at over 110psi air.

The previous trailer needed to be pulled going downhill. This one coast in a slight downhill grade like a car would. Side wind affects larger units much more then smaller ones.
But during accelaration and in hills the weight is there.

I bet you will move to a bigger unit sooner and will smile.

[SmokeyWren]

I've been reading for years from other owners on TheDieselStop how with Navistar diesel engines, MPG jumps up one or two MPG when the engine finally gets fully broken in at 20,000 to 30,000 miles or more. But I guess mine never did get fully broken in, because with 192,000 miles on it I was still getting about the same MPG as when it was brand new. And MPG didn't seem to improve when I did the intake and exhaust mods and added a mild towing tune. The rig was much more enjoyable to drive with the towing tune, but MPG didn't improve. Dragging a 25' medium-profile 5er that grossed about 8,000 pounds on most trips, my MPG was consistently related to speed and terrain and head winds. 12 MPG was the best, cruising at 62 MPH (1,800 RPM) on the plains with no wind. Speed up to 66 MPH (1,900 RPM) and the MPG dropped to 11. Crank it up to 70 (2000 RPM) and the MPG dropped to 10. Add hills or head winds and it easily dropped to 9 or less.

That was with the Navistar (International) 7.3L diesel engine. Your engine was designed and built by Ford, so it may have different MPG characteristics.

[TXiceman]

Our old 7.3L started running better and better fuel economy....at about 75,000miles. But then they dumped the ULSD (ultra low sulfur diesel) on us and the fuel economy dropped.

Ken

[wandering1]

What does your owners manual or the dealer say about the break in period?

[SmokeyWren]

Originally Posted by wandering1

What does your owners manual or the dealer say about the break in period?

The only thing concerning break in mine mentions is to not tow a trailer until the truck has at least 1,000 miles on the clock.

Diesel engines require a lot longer to break in that gassers, because the block and rings are made out of much harder metal. The following is a link to an old article about breaking in a diesel engine. Excellent article that's still applicable to current diesel engines:
Click here to read "Breaking in a diesel engine"

[stuhly]

And of course, no one would stretch the truth about fuel mileage.

[Cumminsfan]

Don't own a Ford, own a 12 Ram CTD. FWIW break in in the Ram manual is 6000 miles. They say to load the motor to promote break in such as in towing. We got our Ram July of 2012, put the 500 miles on it before towing. Towed quite a bit the rest of the year. Now have 15,400 miles on it. Haven't seen any noticeable increase in mpg's.
I tow a low profile 28' 5'er and see 10.5-11.9mpg depending on terrain and weather.
It's total BS when guys say they get over 12.5 towing a full size 5'er with any of the newer diesels. I've read enough towing mpg stories to see that the average towing mpg is around 9.5-12 max. There will be the anomaly with some guy driving 250 miles with a tail wind and thinks he's getting great mpg. All the newer diesel trucks and especially the DEF equipped ones should see 17.5 18 running 70 mph and 18-19+ running 55-60 mph. They all get about the same towing.
Getting 12.5 towing that smaller TT does seem a little low. I would thing you would be at least 13 or better. But I guess that's the goofy thing about towing. Doesn't seem to make all that much difference in whether you're towing a TT or 5'er, there's that 2-2.5 spread for mpgs. 9.5-12. Everyone seems to fall in to that area.
Unless you're towing a boat it's tough to get in the mid teens towing.

[jimcumminsw]

Originally Posted by Cumminsfan

Don't own a Ford, own a 12 Ram CTD. FWIW break in in the Ram manual is 6000 miles. They say to load the motor to promote break in such as in towing. We got our Ram July of 2012, put the 500 miles on it before towing. Towed quite a bit the rest of the year. Now have 15,400 miles on it. Haven't seen any noticeable increase in mpg's.

I would like to see where the manual state that the Cummins engine needs to have a break in period.


The only item on the Ram trucks that required break in mileage is the AAM axles. The ring gear and pinion need to mesh the tooth pattern correctly; this is why the 500 mile break in period is required.

I was at the Turbo Diesel Registry rally this year at the CMEP plant were the 6.7L engine is machined and assembled. The question was asked if there is a break in period for the 6.7L Cummins engine. Ram and Cummins both stated no break in period was required only the differential required to be broken in correctly.

Now that is not to say that after 20,000 miles or so the fuel mileage will not increase in the un-loaded state. Mine increased about 1 to 2 MPG’s; but towing I have never gotten above 12 MPG mostly around 11 and sometimes 9.5 when I run Bio-fuel out west.

Jim W.

[Cumminsfan]

Originally Posted by jimcumminsw

I would like to see where the manual state that the Cummins engine needs to have a break in period.


The only item on the Ram trucks that required break in mileage is the AAM axles. The ring gear and pinion need to mesh the tooth pattern correctly; this is why the 500 mile break in period is required.

I was at the Turbo Diesel Registry rally this year at the CMEP plant were the 6.7L engine is machined and assembled. The question was asked if there is a break in period for the 6.7L Cummins engine. Ram and Cummins both stated no break in period was required only the differential required to be broken in correctly.

Now that is not to say that after 20,000 miles or so the fuel mileage will not increase in the un-loaded state. Mine increased about 1 to 2 MPG’s; but towing I have never gotten above 12 MPG mostly around 11 and sometimes 9.5 when I run Bio-fuel out west.

Jim W.

It's on the Ram supplemental DVD.

ENGINE BREAK-IN RECOMMENDATIONS

The Cummins® turbocharged diesel engine does not require a break-in period due to its construction. Normal operation is allowed, providing the following recommendations are followed:

• Warm up the engine before placing it under load.
• Do not operate the engine at idle for prolonged periods.
• Use the appropriate transmission gear to prevent engine lugging.
• Observe vehicle oil pressure and temperature indicators.
• Check the coolant and oil levels frequently.
• Vary throttle position at highway speeds when carrying or towing significant weight.

Note: Light duty operation such as light trailer towing or no load operation will extend the time before the engine is at full efficiency. Reduced fuel economy and power may be seen at this time.
For additional vehicle break-in requirements, refer to “Trailer Towing” in “Starting and Operating” of the Owners Manual.
Because of the construction of the Cummins® turbocharged diesel engine, engine run-in is enhanced by loaded operating conditions which allow the engine parts to achieve final finish and fit during the first 6,000 miles (10 000 km).

Correct it does not need break in per say, but it needs 6000 miles to reach full potential. Call it what you want I guess.

[tuffr2]

My 2012 F-450 with 10k miles towing a 14,500lb 5er gets 10.3mpg, towing a 7,000lb Vantage trailer gets 13mpg, towing a 2,600lb. boat and trailer get 15mpg and solo gets 16.5mpg.

What I notice is sometimes the truck seems to run better. Maybe after the exhaust is cleaned. Not sure yet. One time I filled the tank and towed the 5th wheel and got 11mpg. Just when I thought it was broken in the next trip on the same road, same direction it dropped back to 10.3.

For now I am going to say the wind was stronger one the 11mpg trip.

[TXiceman]

On the older 7.3L, I was told by the dealer and a couple of good diesel mechanics, to just drive it like you stole the truck once you get past the first 500 or 1000 miles of non towing. Just watch the temperature and back of if it starts heating up.

Ken