Mx13 vs isx Cummins

[JimT]

You're on a forum oriented toward Cummins ISX owners, so by default most of us would prefer the Cummins.

Why are you asking us to pick your truck? There's so much about your current (or future) operation that we don't know.

* How fast do you drive? - That will help determine optimal rear end ratios and transmission combinations.
* What part(s) of the country do you operate in? Flat parries? Rolling hills? Mountains? City driving? Line haul? Regional?
* How heavy are your loads? What kind of trailer(s)? Dryvan/reefer? Tanker? Flatbed/stepdeck/RGN? Do you max out at 80k or haul overweight? They all have different needs.
* What's the mileage and engine hours on each truck? - Higher miles and lower hours means less idling, which translates in to better engine and aftertreatment health. It also helps you to plan for the inframe. On these newer engines that you're looking at, based on typical driving habits and fleet maintenance procedures, you can expect an inframe somewhere around 600,000mi, maybe sooner.
* Is there any blowby? - Short of hooking up to a dyno, you can open the oil fill cap while the truck is running to get an idea of current blowby. Put your hand over the fill tube and feel the pressure, also look for exhaust/smoke coming out the tube. Greater pressure, more smoke = more blowby = less time before inframe.
* Do any of them have an APU? - Greatly reduces engine idling, saving fuel and prolonging the life of the aftertreatment systems and engine.
* What's the wheelbase? - Factors in to you intended operation.
* Have you pulled any rigdig reports? They won't tell you too much, but entries for accidents or citations could help you understand how the truck was driven and whether they had OOS violations for lack of maintenance. Neglect and/or aggressive behavior in one area usually manifests in other areas as well.

These are just some things that will influence an informed decision between different purchase options.