I have driven both and have had more issues with the ISX then with the DD15 I bought a 2013 with DD15 and had a apu installed with a bunk heater and have had no issues with it The last company truck I drive was a 2015 579 Pete with a ISX 15 that had just had a full overhaul on it and it only had 280k on it when I started driving it the truck had an apu so I didn't idle the truck And about every 2 weeks they were having to hook up the computer and doing a forced regen on it The filter was baked when the engine was overhauled. I was with that company for 6 months and put about 60k on truck I was told by shop that that year had a pre filter to the DPF filter that was causing the problem which had been changed too when engine was rebuilt The truck I bought with the dd15 had 460k on it and the dealer baked the filter when I bought it and I have put 50k on the truck with no issues
I have a 2012 truck with an ISX and just shy of 700k on it. I have the records on it from the fleet that had it and all it has had is the regular emissions services every 250k an EGR cooler was replaced early in its life as well as NOx sensor, I replaced the EGR valve recently. These stories of the motors failing are due to not maintaining the emissions system according to the manufacturer recommendations and not running an oil sampling program. Issues that plug a DPF like bad injectors could be avoided by sampling the oil every 25-30k miles. If you are buying an emissions truck, if they can't provide records the maintenance schedule has been maintained on the emissions side, don't buy it. If you can verify those records, buy it, put fresh oil I. It, run for 20k on it, and do an oil sample. Oil sampling, in my opinion, on an emissions motor is not a choice but a necessity. You can save yourself thousands by spending a couple hundred bucks a year on samples. As far as ISX vs DD, they'll both get the job done. If you're going with a manual get the ISX or X15 as it is now. If you're going AMT pick the DD to take advantage of the latest generation of integrated power train goodies.
Get a DD15 with asymmetric turbo. If you want the AMT, get a DT12. The integration with a DD is much better than with a Cummins setup. More features and components work better together. For instance, if you like adaptive cruise or connect Diagnostic Link to monitor signals--just makes more sense to have something a little more proprietary.
A 2014 t680 (isx15) we have in our fleet had died out at half million and they end swapping into a year newer isx15 they recovered from a totaled truck. Never know if they improved the isx and now we need to see how long the new X15 lasts.
Currently in a Volvo D13. Been okay for the past 2 years. Have had to change a Turbo at 550k and a flex pipe. I just don't know how the emissions last on these things
I am a Volvo guy too. In a 2012 D13 I shift currently. Been pretty good to me compared to all the other trucks horror stories i hear about but that issue with the derate Scr fault really got me traumatized. Changed the Nox sensors yesterday and got about 500 miles on it today. Crossing my fingers that changing the Nox sensors did it.. if Not, im trading it for a dd15
