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6.4 reliability

158K views 32 replies 15 participants last post by  INJEKTER1 
#1 · (Edited by Moderator)
I was considering the possibility of buying a diesel truck with a 6.4l. How reliable are these engines as a daily driver and weekend towing rig? Should they be kept in stock, or a tuner be added? Have you heard stories of lousy fuel mileage? I was wondering what kind of fuel mileage they get. Any help would be appreciated.
 
#2 ·
There are a ton of problem free 6.4's and there are a ton that are complete pieces of sh!t, mine was the latter. I would buy a late model 6.0 or a high mileage 6.7 or a Dodge or Chevy before I bought another 6.4. They do get horrible fuel mileage, at least mine did and they are maintenance queens but if you delete them and run a mild tune and take care of it you may have a good truck or you may not. Pure luck imo
 
#3 ·
If you want a motor that will live forever... Buy an 06 5.9 cummins... You will spend a good deal on suspension and trans parts... But the motor will out live the truck by a long shot.

The 6.4 isn't known for longevity, it is known for power. It can be VERY reliable if you take care of it. That being said, if you are buying it used you need to know the past. If you don't pass on the truck... The newer diesels are all very expensive the moment the warranty runs out. Any way you go though, diesel is expensive these days.
 
#4 ·
Check it out yourself, the reliability of the 6.7 and the 6.4 are the same. There are plenty of online resources that will support this statement. Their is a relationship between power and longevity. The F550 and above are detuned to provide more commercial like service, something like 50% longer life.

In my view you should learn about each engine/drive train technology and decide what works for you. Diesels are poor daily drivers. They are work trucks. It has been shown that the present gasoline engine truck is much better for daily driver/ occasional tow vehicle. Plenty folks here purchase these trucks for their power, speed, looks, and a place to dump lots of cash. You want a race truck, then go no further, the 6.4L can't be beat.
 
#6 ·
The only down side of a 6.7 is the cost... They are great motors, but like anything they will break sooner or later. You just better hope that whatever breaks does so under warranty... One thing is for sure, parts and labor for a 6.7 are no cheaper than a 6.4... It is quite the opposite.
 
#7 ·
I'm not sure about that. Correct me if I'm wrong but for an example an oil cooler for a 6.4 is about $260 and is buried in the valley and the oil cooler for a 6.7 is about $100 and on the bottom side of the engine. A set of turbos for a 6.4 is $1900+ and a turbo for a 6.7 is $1400 and the HPFP are about the same cost.
 
#8 ·
If you want to talk about part pricing and job difficulty its all tit for tat. 7.3 parts are still expensive, diesels in general are expensive.

To what he was asking, i have put 30k on mine in the last year as a dd and tow rig whenever required with only 2 issues to date,
1 being a transmission temp sensor which was a perfect opportunity to service the trans, 2 the clock spring just started acting up.
the truck has 132k on and i love i just deleted the dpf this week and it is a totally different truck.

As far as maintenance i change the oil every 4k miles and fuel filters every other oil change, i did the same with my 7.3 and i recommend the same for all vehicles so its not really anything extra for me.

My driving is half city half 50 mph country roads in the summer i got 12.5-13 mpg winter 11-12 depending. that is with 3.55 gears and 35" tires.

Also i would recommend a tuner even if you leave the dpf on because then you can do a parked regen which cleans better and completely which will help with mileage. A good fuel additive will help to i use standynes performance formula but there are a lot out there.

Hope this helps with your decision.
 
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#9 ·
I sold my 2007 5.9 so that I could buy a 6.4, it was mostly because of the power aspect. If you want an awesome truck that you could mildly tune while still using it as a daily driver/weekend warrior and get decent mileage look for a 2006 - 2007 5.9. The 6.4 is an awesome piece of power when you tune it out, however I would recommend deleting everything if you do go the 6.4 route. That's not going to be cheap though a couple thousand dollars minimum on parts alone if you do it yourself. Now that I've deleted everything it runs pretty decent, before it was deleted the DPF was throwing out consistent codes and was always posing a problem. I would also look into deleting the EGR thats just a ticking time bomb. Fuel mileage does suck, on the same token its a truck so I can't imagine your expecting VW TDI or Prius numbers.

My vote for you would be get a 2006-2007 Cummins, find a SMARTY Jr., throw in a torque converter and a valve body and you'll have what you are looking for.
 
#10 ·
as others have said, these Diesels are expensive to fix, and so are BMW's....but a turbo-ed diesel is super cheap to make power with...i like the power......mine is a daily driver and ive had little issues with it, but when they happen, they are not cheap.....fuel milage un tuned is horrible, tuned its passable but its not a toyota the guy with the 2014 6.7 sounds a little jaded ,,, ive had 2 6.0's and would not go back there
 
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#11 ·
So the 6.4 is a reliable motor and sounds like less problems than the 6.0. It will not be used all the time as daily driver, I have a small car for that. It will be used on weekend mostly for weekend projects and used to tow camper when we purchase one. I said daily driver because I figured I would like driving my truck more than driving my small car.
 
#12 ·
Do reading and research... That is all I can say to you bud. They are great trucks, I love mine. But you need to understand them to keep them working well.
 
#13 ·
I have an '08 with 111K. I tuned and deleted at 108K. The only issues the truck has had are front seals at 52K, 1 battery at 90K, the other at 102K, blend door actuators at 100K, reflash for P0088 at 100K, driver's seat heat element at 100K. I have done brakes at 105K...shocks coming up. It gets oil changes every 5K, fuel filters every 10K, trans service at 60K-next at 120K.

Economy sucked before the deletes. 7.5-8 towing my 20'/7K cargo every day. 11.5 mixed and 14 hwy. Since deleting, it's increased to 11 towing/mixed (I like not having to putt in town so I mash the skinny pedal pretty good) and 18 hwy. The 3mpg gain towing is saving me right at $40 a week in fuel expense, so I should recover the costs on the deletes in less than a year, on top of having a more dependable truck.

It seems like most of the horror stories are related to deleting, running big horses, and driving the snot out of the trucks. The truck isn't a race car, no matter what ya do to it.
 
#14 ·
To me, reliability of a well designed product is determined by the quality of the assembly process and the parts suppliers. This in combination with proper maintenance determines real reliability. I suspect all brands of $40K plus diesel trucks have a certain and same degree of quality on the drawing board. Afterwards, it probably boils down to the profitability as it relates to quality of parts, assembly and the target market for the vehicle. This accounts for everything from the discrepancies between similar vehicle owners in satisfaction to overall sales between competing companies.

As for me, my '10 F-350 has been trouble free for 120 k miles. Of course, that comes at a higher than normal vehicle price in maintenance, even when I do it myself. It also means turning off things that weaken a flawed EPA required design. I'm going to knock on wood after this reply, not because I am superstitious, but because things eventually break. But until then, I will continue to pull my toys around and yes, use as a daily driver.

I'm good with mine as I am sure the vast amount of 6.4 owners are as well.

Cheers

2010 F-350 4x4 Lariat CC LWB 3:55 10300 GVWR - KEM 485 for good measure
 
#15 ·
How is the fuel mileage and what are you towing? I understand it is truck and it is not small car. I have full size truck that gets ****ty gas mileage, but I am looking at getting ok fuel mileage when driving and understand that it is heavy and when toying big it will decrease mileage.
 
#16 ·
Im new around these parts, and have only had my 09 F350 for a few days now, but im not seeing what these guys are seeing in relation to mileage.

On the 5 hour trip back after purchasing on Wed, I had the cruise set at 73 cruising through the Ozark mountains, and averaged 17.6 for the trip. Was near 18 before I hit a regen 200 miles in.

Truck is 100% stock, single rear wheel, 4x4 with 115k miles. Runs like a top. Now, I do have over 5k worth of parts sitting in my living room waiting to get put on tomorrow, but, it seems to be a fantastic truck in stock form from what I can gather so far.

After 2 days of driving around town, and a bit of highway, sitting at 16.4 mpg averaged. This truck blows the doors off my 2006 F250, and even more so off my old 2008 Chevy 2500 HD with the Duramax. Not even in the same ballpark IMO
 
#17 ·
Landcruiser is that hand calculated or the dash display for mpg the dash in not very accurate. I love my 6.4 almost more than my 7.3 but there is a big fuel mileage difference. If you are ok with removing the dpf you can expect probably 14-15 mpg empty mixed driving and less towing it all depends on how you drive, where you drive and what you tow.
 
#18 ·
Do your homework on the truck including oasis reports and Carfax than go for it! Everyone I know that has a 6.4 loves it! Don't go Cummins( Cum-Apart) unless you want the speed sound and power of an antique farm tractor! Oh and keep your eyes out for a nice 6.0 If your not dead set on the 6.4 i love mine.
 
#19 ·
Fordman, that was just off the onboard CPU. I realize they are not too accurate, but thats all I had at my disposal and its running factory wheels and tires, etc. Figured it cant be too far off.
 
#29 ·
its off,, no doubt....but you dont need us to tell you what we already know.... set your trip meter and figure it out for self on fill ups....and please report back......: )
 
#21 ·
If you are looking for data as apposed to opinion then look for the B50 Meantime to Failure value for each truck year and model. For example the B50 value for the 6.0L Ford engine is 350 to 375K miles.

Perhaps the 6.7L is different than the 6.4L in maintenance. The 6.4L require attention to maintenance and good low sulfur fuel.
 
#23 ·
^^^^^

People don't realize that one of the issues with a cummins happens to be melting pistons... What comes along with the most un-reliable injectors on the market??? Ohhh yah, melted pistons and trashed blocks.
 
#25 ·
I got 17 once on a 300mi trip while stock. It isn't impossible, a lot depends on fuel and wind. But remember, the regen process will eat into that massively. My lie-o-meter is telling me 17mpg right now. My actual is somewhere around 15.5-16. For any diesel that is acceptable, I don't care about fuel economy though. If it was a concern why the f would I DD a diesel? I drive my truck because it makes me happy. That is the reason I own it. It is nice to see higher numbers because fuel is expensive, but I would rather see my truck last longer. I care more about what my deletes do for my truck than fuel economy. The difference in how it sounds tells the story for me.
 
#27 ·
There is no doubt the 6.4 has more piston problems, but there are quite a few cummins motors that get trashed by injectors hanging open... At least our injectors actually last as long as we keep the fuel clean.
 
#28 · (Edited)
My Crew has the 3:55 gears and I run 33" tires. I have tried several tunes but my favorite are both from KEM. I run the 485 while towing and the 210 as daily driver sometimes. The 485 yields me 15.5/19+/- city/hwy mpg hand calculated. The hwy mpg of 19+/- is keeping the rpm under 2000. Towing my 12K fifth wheel mpg is about 10-13 since I have mountains to cross. The 485 does fine with exhaust temps as long as I am paying attention. I have my CTS alerts set for 1100 degrees. and rarely reach that since I'm in no hurry on the inclines. I am running a turbo back 4" exhaust. I header wrapped the down pipe as to not allow too much heat to the fire wall. I figure that lowered the PGT by 50-75 degrees.

I hope this helps.

2010 F350 CC Lariat LWB 3:55
 
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