Pullin with the dreaded PACCAR Mx13

Congrats on the truck purchase. Only way to find out if it’s a good one or not is to go out and run it.

 

On the lower HP mx13’s the torque curve stays flat to a higher rpm than the 510. On the 510 the torque starts dropping off around 1200 whereas on the lower HP ones the torque doesn’t start to drop off until 1400 or so.

 

That might be so, but you’re not saying the 510 hp tuned engine is making LESS torque (in an absolute sense) at 1200 RPMs than say, a 455 hp like mine are you? Not saying I know what’s what or anything but that would be odd considering a higher HP is simply a number derived from a higher amount of torque over a period of time. You’d assume a 510 hp engine would be making more torque over a broader RPM range compared to a turned down version of the same engine.

 

I got burnt by MHC for my paccar engine for 19,000
I’ll never own another.

 

I've ran 20k on oil and sent a sample in once. It looked fine. Standard white bottle 10W30 Rotella so not even the top shelf stuff.

You might have a point though about the Bioblend diesel. That's a whole topic by itself but I have also noticed worse performance and more regens using it. Even the Espar cab heater hates it...coughs a lot more smoke out of it's tailpipe when it starts up and sometimes doesn't even light off right the first time. I'm in WI an MN a lot a usually fuel in WI at the Petro in Portage. Last week though I went all the way out to Bismarck on a longer one and ended up putting on 150 gallons at the Petro in Clearwater, MN on the way back. Sure enough about 500 miles later a dash light comes on...something about DPF backpressure sensor voltage or whatever. Truck throws the fit and goes into many regen cycles over the next couple days. Unusual behavior. And the cab heater was smoking a ton on startup as I already mentioned. Filled back up in Portage, WI again Monday with the Wisconsin fuel and everything is back to running clean and normal again and the warning light went away. Minnesota fuel is heavily bio-blended crap as mandated by the state. Same with Oregon. Loves bio blend fuel (anywhere) also tends to get complaints from people who pay closer attention to this type of stuff, so I avoid them completely. I've also noticed in my 7.3 Ford engine the yellow B20 bioblend fuel from MN and OR always made it run like a dog and lose major MPG pulling a travel trailer compared to the totally clear colored fuel in Montana that ran great with hardly any smoke.

 

The 510 produces more torque across the curve but drops out of its peak torque at a lower rpm. The lower HP models have a long and flat torque band where they produce 1650 torque at 1500-ish rpm versus a 510 producing 1700-something instead of 1850.

 

Ironically, it was near Madison, WI going through those hills on the interstate with a 40k lbs loads I had problems with an injector that was almost brand knew that blew a seal. I don't want to be completely against the MX13 because its a reasonable motor when running lighter loads and alright for fuel economy. However, it can't take the pressure when the weight is toppoing out and not as tough as good as the 3406B CAT I ran an older one with 340k miles on it in 1996. It hauled 45k lbs like nothing going through the WV foot hills. And even the older Cummings N14 in 2001 to 2001 that ran me all over the Usa and never had one problem besides a slight oil leak which the owner at the time didn't care to fix it. Besides regular maintenance those motors hauled. For years, the company I worked for had Volvos as well with D13's and again no real issues however, freight was light so its difficult to really gauge the progress in comparison. I remember in '97 driving a Detroit 60 series in a Freightliner and that motor hauled like nothing with over 200k miles on it. Again, no real problems. I've heard from others in the waiting rooms at Peterbilt that the X15's would of giving me more problems with turbos etc. If I had chosen to go that route however most mechanics I speak to are telling me for the general freight I'm hauling within the 40k to 45k lbs loads they can pull the weight better overall. Either way, I have to figure out something soon because if this allegedly capacity purge is coming and the amount of calls and emails I'm getting I need something more reliable. I've treated this mx13 motor well and its not balancing out.

 

If I decided to buy a truck again I’d order either another Peterbilt with a Paccar or a Western Star with a Detroit. Based on trucks around me there’s no way I’d personally chance an x15 but I’d be willing to try a Detroit simply because the local dealer is open 7 days a week for service.

The guy I work for is down to 5 or 6 x15’s now and those are getting weeded out while still fairly low mileage. And that running heavy, idling to offload using the pump, and probably a fair amount of drivers who don’t turn their truck off all day.

 

I will say this
'' the 510 hp tuned engine is making LESS torque (in an absolute sense) at 1200 RPMs than say, a 455 hp like mine are you?'
yes'
hp is just torque x's rpm.
Also a turned down engine is completely different than a high hp 1.

 

I'm on my second MX13, first one was a 2019 that had no engine issues in 530K miles other than the usual sensors, and a couple of issues with the wire harness. The 2025 has struggled with the injector issue like all others of it's generation. Many flushes, couple or replacement injectors. Finally got six new injectors, and was told by the local dealer they were going to be the new generation. Got a fuel pump code two weeks ago, put it into another dealer and found out the new injectors were first generation, not the new ones. So, six new second generation injectors at 315K, under warranty, and the local dealer is off the Christmas card list. I'm funny like that. Trust is hard to earn and easy to lose.

Overall, the MX has been good to me, running 80-90Kgross in the Pacific Northwest. I don't see any evidence of the MX being unsuitable for heavy loads, we pull heavy in the hills every week. It checks a lot of boxes, including weight savings, economy and reliability . The biggest negative is the limited service network and no real support outside the dealer network. We're looking at a Detroit, but, well, it comes in.a Freightliner.......