Can you use Ultra Low Sulfur Diesel with the XRT Pro's High Sulfur tune?

I recently purchased a 2011 Chevy with a Duramax LML engine that came with a XRT Pro tuner by H&S. At first I was planning on uninstalling the tuner since I discovered that H&S had went out of business and I felt messing with the computer was way out of my wheel house. However, when I reverted to stock I got messages about the emission fluid system needing service. I did some more learning I have confirmed that the emissions system has been gutted (DPF deleted and DEF fluid tank removed). I talked with my local mechanic and he seemed to indicate that having the DPF delete was a good thing and I would be better off without it. So I reinstalled the tuner. Following the instructions on the screen I selected the options for the emissions system being removed, but the tuner seems to call this mode "High Sulfur"

My question is: does this mean I need to look for "High Sulfur" fuel to put in my truck? (if so where can you even find this??) or is regular ULSD fine still? The manual seems unclear about this, is there a separate tune for DPF delete with ULSD?

Additionally, is the XRT Pro still the best tuner to be using for this truck? Our primary use for the truck is we plan to use the truck for towing a fifth wheel for full time rv living. I read in the forum that the H&S never optimized for mpg, is there a tuner that would be better at optimizing for mpg for picking up groceries and such but can be updated to optimize for performance when towing?

Thank you, thank you for any help. I am new to all of this and have a lot to learn!


  • The wording "High Sulfur" is simply that. Nothing more. You can run ULSD with no issues. The wording basically means that the DPF has been removed and the tuning has disabled anything associated with it. Could you run High Sulfur Diesel? Sure, but as you said, you would be hard pressed to find it.

    As for the tuner, usually if it loads and works, you will be fine. I assume you have looked at the manual and know that you have 4 power settings.
    Power Levels
    Stock.. . . . . . . . . . . . . . . . . . . . 0 HP
    Tow.. . . . . . . . . . . . . . . . . . . . 50 HP
    Street.. . . . . . . . . . . . . . . 100 HP
    Performance.. . . . 150 HP

    Typically the best fuel mileage is obtained by running the tuner on the highest power level. You could use that for traveling unloaded. When you tow, drop it down to the tow setting. With that said, all trucks are different. You can experiment with the power levels to see which one will yield the best mileage. I would not tow on the Performance power level. Also keep in mind that your fuel mileage will go up once the truck relearns your driving habits after the tuning was reloaded. Usually about 500 to 1000 miles.

    To change the power level you will need to go to the tuner and select Change Power Level from the main menu. You do not have shift on the fly available with your make and year.

    Hope that helps..

  • Awesome, thanks Smokin08!
  • @daprnedgo
    One other thing I would recommend.......... You mention you will be traveling most of the time. I would always carry the tuner, cables, etc. with you. Put it in a nice safe spot in the trailer or truck. That way if you have a brake down that requires repair at a shop, and for some reason the ECU gets flashed or changed, you have the tuner to reload. It would be horrible to be 1000's of miles from home (where your tuner is) and get the truck out of the shop but it won't run. Then you fly back home and get the tuner to reload it or buy another one. Know what I mean?
  • Makes sense
  • I also did a delete with HS mini on my 2011 LML, not really seeing much mileage change. I guess I’ll try the highest setting, putting on a lift pump.
    One question is, can I run Farm diesel in it?
  • edited July 2019
    What is H amp;S
  • If you load the delete tuning you can run farm Diesel in it. I wouldn’t though. If you get caught you’re going to get one hell of a fine. As far as mileage the tunes were written for power/performance not fuel mileage.
  • Thanks. Anyway to tell if your Minimaxx is a real one or fake?
  • Not really. If it's newer than about 2014/15 it's a fake.
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