Pacar MX Engine fuel mileage

Update regarding my 5 MX powered T-660's.
Mileage: Five units ranging from 70,000 miles to 80,000 miles.
The fuel mileage and performance of these units showed substantial improvement after the 50,000 mile mark. The fuel mileage is ranging from 6.6 to 6.9 mpg driving economy. This is close to a full mpg gain over the initial break in numbers. Mechanical issues after software updates have gone away. I am having zero problems with these engines now and the T-660 chassis is very good. These engines don't use any oil. I have never seen an engine go so far without adding any between changes. Oil analysis look very good.

 

Thanks for the update.
Please keep them coming from time to time , it is good to get real world feedback.

 

Hi, I'm driving a T700 with MX engine.

Very unhappy with fuel mileage and performance. Dealer and Kenworth have done everything in their power to find out what's wrong but cannot find anything.

No big problems with the truck untill March this year. EGR valve needed replaced, connectors DPF system had water in it... Not long ago fan hub broke of and ruined fan and rad... Don't have to add oil...

Almost 200.000 mls on it now.

Average fuel mileage 100.000 lbs grossweight is 5.2 MPG. Tandem loads it's 5.7 when the weather isn't too bad.

 

Hey fland im from moncton so i know the roads you travel on i'v got a 2012 386 full areo package with the 455hp/1650tq and 3.70 rears, i'm not sure how your truck is spec'ed but i know mine with all the hilly roads it doesn't give up fuel economy very easily it makes you work for it, i haven't done tri axle in awhile but when i did i always avg right around the same as you 5.3-5.6.

Biggest things i'v found is is gets its best economy around 1350-1375 rpm and with the 3.70's puts me right at 60mph/97kph, watch your boost try keep it no higher then 20-23 its hard to do with heavy loads cause this motor isn't afraid to make you drop gears and crawl up a hill and don't over rev it or lug it too much so no need to go over 1550rpm i usually take my splits around 1275-1300 and full gears at 1200.

Doing all that i can easily leave toronto with 35k in the box and make it to moncton and avg 7-7.3 in the summer winter 5.8 at best anyway i hope those tips help ya or anyone with this love hate motor lol

 

I find that pulling a hair under 80,000 on 84 s ct with an mx455 3:36 ratio 10rr pulls very well , only have to drop one hole before Ruby rd , otherwise I've been seeing low 6.5 to as high as 8.0

 

Thanks for this information, really happy to hear other guys about the MX...

My truck was spec'd with 3.55's and a 13-speed ultrashift. From the first day off I have complained about bad fuel mileage and later on also about bad performance. The truck had worse fuel mileage compared to my old truck, an International 9900 with C-15 1850 torque. I had expectrd it to be at least 5 to 10 percent better...

High engineers from Toronto came in and decided that I needed 3.70's instead of the 3.55's. That didn't do the trick. I had truck spec'd with 455 HP, was way cheaper for warranty. The engineer guys changed it into a 485, which also didn't make any difference...

Turbo boost of mu truck is 29 Psi. But when leaving after a stop the boost goes up to almost 40. Needless to say the truck seems to work better too, according the fuel economy meter the mileage is way better too..!! The high boost also shows randomly, when you don't expect it. Driving with an other guy on 185, with simular loads and just being able to keep up with him. then suddenly at the third hill there's plenty of boost and torque and i fly by like he's standing still. It just doesn't make sense. That extra boost is there but only for a moment, or ten minutes...

I had the EGR valve changed. The first trip after the repair the truck worked great for about 5 hours. Fuel mileage like never before, high boost, great performance. Broke all records untill Riviere du Loup. Then the old truck was back again. Boost gone, fuel mileage gone...

I've been driving around with a data-logger in it. Engeneers have studied engine behavior and can't find anything wrong. Motor is working the way it should, I have to live with it. I know that somewhere inside that truck is a great working engine, only it's hiding. Every now and then it peeks up and shows what it is able to do. Most of the time however it works like an old lady, with slow upcoming boost. Sometimes boost (and torque) takes too long to show up which makes the transmission shift back again...

After two years working like this with a 150.000 dollar truck I'm pretty well done with it. I've had enough. There is however no way of getting out of the truk because a 2011 T700 with Paccar MX and Ultrashift isn't worhth a dime. I'm stucj with it for the next two years at least...

Don't get me wrong, it's a great truck to drive but it's very frustrating knowing it could do so much better then it does...

 

I know what your talking about fland this motor has so much potential that it's not using all because of epa reg's. From what i gather when you first start the truck and take off and the boost goes up to 40 is because the ecm is feeding more fuel to the motor to get high exhaust temps to get the DPF up to proper running temp, and it's basically the same thing when your already running down the road and boost will suddenly go up to 40 it's doing a rolling regen burning off all the crap. i know i love when it's doing a burn because ya it's like a different animal under the hood.

I did some research on this engine awhile back and i found in europe that they released this same engine with some major power 510hp with 1850tq so i know this engine can put out some power i had found an add awhile back about a guy around truro that could program them to work better i'm just trying to remember where i found it at.

 

This is very usefull information, thanks for that..!! Why are you the first one who tells me..??

Next year in the 2014 models there will be an MX with common rail (like the Euro 6 version) with 500 HP and 1850 torque. It might be that the European and the American version will be the same then...

Jeez, it's that simple. When i got the higher boost it's doing a regen... Why did I never think of that..??

 

Good information for them driving an MX and not happy with performance and fuel-mileage. There is hope..!!

My truck never performed well. Didn't pull well, slow boost, bad fuel mileage. Things changed. Since last Sunday it's working fine. Fuel mileage is up 10 - 15 %. Less shifting, pulls like never before...

I got no clue why, it doesn't make sense to me. Hope it will stay this way. If things can change for the better so suddenly, it wouldn't surprise me when it changes back to its old miserable self again...

 

You don't say if your truck is new, sometimes trucks are programmed to allow a breaking period for the engine.