Caterpillar MPG anecdotes

Early DDECs have proven reliable and we’re/are very popular
3406e also have proven their worth over time
The 3406 will require more driving finesse to gain mileage than the 60 series
I’d urge you to stay away from the 6nz or any other C model cat
I’m sure others will disagree because the 6nz is always touted as the big strong etc etc....but imho there low mileage and unreliable over the long run

 

If I had the drive to keep driving, and the cash to buy enough 6nz or 3406 engines, and a couple trucks in the barn just waiting for their time, maybe I'd consider staying at it. My 389 is stock and fully operational, never any major emission issues. I carry a box of sensors and know my way around cummins quikserve so a couple times change a sensor and good to go again. It has been a good truck *knock on wood*, but I'm just waiting for something to pop. It is not confidence instilling the way that old 6nz was. I'm too young to look at this industry and think there isn't an ever increasing level of nonsense to deal with from every angle to seriously say I want to do this for another 30 years, let alone half that. If I was nearing the end of my working years, sure, I'd probably opt to spend the money on an older engine that will last longer than I would care to drive it. Running old is a fine idea but that isn't sustainable over the long term, or if you ever want to have any decent size fleet.

 

The thing about this day and time with electronic tuning etc is folks have forgot a lot of hands on diagnostic work. Electronic or mechanical engine they are the same as far as what makes them tick.

Air in the fuel
Low fuel pressure
Restricted air filters
Over head out of adjustment
Boost leaks
Are all things that will hurt performance and overall fuel economy.
Exhaust leaks before the turbo
(Even a very minor almost unnoticeable leak in the exhaust before turbo or in the pressure side of the intake is a big deal)
Timing
As well as look at both turbo wheels. Run the proper turbo for your setup.
And when checking for boost leaks don’t just plug off the air to air and call it good. Pressure the whole system from air inlet of turbo to the intake.


Most have a minor issue and rather than check anything they run and tune it. If you ask em have they pressurized it to look for boost leaks first thing they say is well I’m makin x lbs same as always. Well it takes a huge leak to loose pressure and 30 lbs under seal and 30 lbs with a leak is day and night difference.

No matter the engine it’s gotta be right and run properly to get any sorta economy.

 

A 30 to 40 k rebuilt cat 6nz in eastern Canada is just a patched up engine I’m guessing..Good rebuildable blocks are hard to find . More often than not you need to find one that’s in a beat up truck and buy the whole truck plus hope it’s good.. old school guys buy every reasonable block they come across to keep for future rebuilds it seems.

 

Best mpg any of our CATs got was about 6.2-6.3 lifetime. It was a 3406E 6TS in a 98 379 extended hood with a 63” standup, 265” WB and 3.55 rears with a 13 speed. I can’t remember if it had tall or lo pro, but they were 24.5s. It pulled a hopper probably all but a couple months of it’s 8 year tenure with us. We bought it used with a little under 100k miles and it left us with nearly a million and opened up once for bad liner and blown headgasket somewhere around 600k miles.

Most of our CATs ran around 4.75-5.3mpg with a mix of cattle pots, hoppers and a stray end up here and there. The aforementioned 3406E, two 3406B engines, a couple of MBN bridge engines (which everyone hates, but ours were great), a BXS, two MXS and my NXS W9. All the ACERT trucks ran the same specs, 18918B transmissions and 3.36 Eaton rears on 24.5 lo pros. The NXS averaged the worst, 4.75 lifetime. But I drove that W9 like I stole it.

Never too many issues, other than one MXS liked to run hot a lot when it was younger. It eventually turned out to be the thermostat housing not letting the thermostats open up all the way. Hired hand ran it hot hot once and cracked the head. It was the only ACERT we ever de-ACERTed and it never ran quite right after that so we didn’t fool with converting the others. My NXS was the most trouble free engine I’ve ever had.

All these engines except the MBN engines were 550/1850 rated. The MBN engines were 475/1850. To me, they pulled just as hard as the 550 engines did except for the 3406E. The E model pulled the best out of all of them.

 

Just for curiosity. What’s the danger point of to much hp on a c15 acert. Motor tag says it was built in 06

 

I liked my MBN in the truck in my avatar pic after the MBN part was fixed. Ran it stock for a short time after buying it and that was frustrating. After a "proper" tune, turbo and few other minor upgrades/fixes it was a legit 550/1850 and ran like a top. Wasn't the right truck for what I was doing but I was making good money with it and didn't give a ****

 

Stay at 550. Watch your egt's and water temps like a hawk always and keep them in check. It'll last a long time. More than that you'll need much deeper pockets than I've ever had.

 

My t660 with c16 and 13 speed did 6.75-6.85 last 3000miles pulling step conestoga but with very light loads ( around 30k and 68-70mph )

 

I have the same engine and my overall average is 6.5 mpg with a diesel powered APU. It has over 1 million miles on it.
And I'm not afraid to idle it.
The fuel consumption is not the most important part of the equation.