Pete 386 with the Paccar MX engine

I don't really care where they are BUILT. What matters is where they were designed and who designed them and for what. Also who supports them is a huge issue. If the engineers that design them are half way around the world, then expect issues.

 

What ratio rear end is in the truck? You can have the most powerfull engine on the market, but if its geared to tall, any engine will struggle up steep hills.

 

This is one of the most often quoted fallacies.
On single reduction axles it is the overall gearing combination of diff ratio times the particular ratio engaged in the gearbox.
Although you may have to drop a gear or two in a very tall geared truck once you are in the same overall ratio (gearbox X Axle ratio) as the lower geared truck you will pull the same.
In other words you should climb the grade at the same speed.
You could obviously lose speed because you are trying to climb in the higher ratio but this is a driving style that will need to be adapted and not the engines ability.
Gears will also have slightly larger spacing but this is almost negligible.

Often the engine may have a different performance characteristic and needs this to be established to get the best climbing performance and or mpg.

 

I drive a 455 mx in a 660 Kenworth. So far at 50,000km it gets around 5mpg us at under 80,000lbs. When we load to 100,000lbs i get around 4mpg ..My 2004 Pete 379 with a 475 cat got 5 mpg at 100,000lb and twice the speed going up 9% grades..Now it is 20 mph rather than 45 mph with the Cat..Not impressed with this piece of junk..

 

Our 430hp DAF (MX predecessor) motors outpull the c13 CAT motors with the same loads on the same route.

 

I have a 2013 with the mx 455. 105000 miles on it now... Fuel economy is poor.about 5.4 pulling a curtain side..09% idle... Blew up at 13000 mi. Complete new engine.. Random check engine light... Been in the shop 6 times...

 

What went wrong at 13 000 miles?

 

Pretty much all the MX engine we have out are not doing great on fuel milage. I have never saw one over 6.5 mpg. We see the same trucks same speck and year with the Cummins ISX getting all the way up to 7.5 mpg. We see Volvos getting over 8 mpg. The MX is not a powerfull engine but most drivers say they drive nice. Our shop has not saw many mechanical issues with the MX but tons of electrical issues and EGR / Aftertreatment issues. Cummins has had more mechanical issues but updated both the pistons and block over a year ago. The Volvos have almost no Electrical issues but tons of injectors / cup issues. The new MX and Cummins engines are just starting to show up at the dealership. They both are improved we will have to wait and see how much. One thing I really like is the Aftertreatment ecu has been eliminated which eliminates tons of wires.

 

I have a 2011 Paccar with 18 speed and 3:55 rears. I average 7.5 mpg in the summer and down to 6.5 in winter. With that being said, I will take little credit for that. I don't run fast, I take off easy, and I shut the engine off most of the time. My option if your looking at getting a new truck with Paccar I would wait until they come out with a higher torque which is suppose to be soon.
I pull a flatbed with soft sides and have a 244 wb.

 

Anyone care to update this thread? Seems like a lot good info already & updates/tweaks to both the MX & Cummins should be getting some miles on them...