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  1. #21
    Big Traveler
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    Quote Originally Posted by Chiefblueman View Post
    Knock sensors working with ECUs in modern vehicles all but eliminate audible knock. When knock is detected via piezo knock sensors the ECU pulls timing back to quell knocking. This also can result in less power produced. Running a quality top tier premium gas should allow your engine to use more advanced timing and could result in better power. The higher octane fuel should reduce knock. If an engine is designed to run on regular, running premium generally will have no effect except that on your pocket book. Using high octane fuel which has a slower burn rate or flame front without advancing timing, timing curve and/or increasing compression ratio is ineffectual. This is why some engines today have dual power ratings, one on regular gas, the other on premium. I doubt the GM 6.0 is one of them.
    My guess is the additional nearly 1.5k lb curb weight difference would hamper performance between two engines of similar power ratings. 100 lbs will increase 1/4 mile acceleration by about .1 sec or about 1.5 seconds for 1500 lbs, a considerable amount. I would also surmise the tires and wheels on the 2500 have more rotational mass which can have a perceivable effect on performance. Gravity, weight and mass all affect performance.

    You've purchased a larger, heavier vehicle with a heavier drive train having more rotational mass requiring more power to spin it and using an engine with similar power ratings. For comparison, add about 2k lbs to your 1500 5.3 towing set up and report back. I suspect there is little wrong with your truck.
    Very well stated Kim,
    Premium fuel on an engine calibrated on regular and as long as knock is not present will do nothing for performance. This test is to determine if there is excessive knock. My 1500 under heavy load will pull back some spark so I tow with 89 octane fuel which is just enough to prevent knock under heavy load. As a result I am getting peak power and better fuel economy while towing. For non-towing I burn 87 octane and only from top tier stations. I agree the extra weight of the 2500 is most likely making the difference but it was the chucking comments that also caught my attention so looking to make sure peak performance is there may be warranted.

    Curious also if the OPs trailer is level on the 2500? The 1500 would have had a lower stance so the attitude of the RV could also be contributing to a different tow experience with respect to the chucking.
    Last edited by MidwestCamper; 06-16-2019 at 02:52 PM.
    MidwestCamper

    Jim & Dawn
    Near Milford, Michigan
    2017 Imagine 2600RB
    2015 GMC Sierra 1500 Double Cab 4x4

  2. #22
    Site Sponsor Cate&Rob's Avatar
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    Good discussion Kim and Jim. You guys are both good at this !

    For what it’s worth . . . (a bit of an “apples and oranges” comparison) . . . My Ecoboost tows a lot more comfortably on premium fuel. I expect that this is because of better spark advance.

    Rob
    Cate & Rob
    2015 Reflection 303RLS

  3. #23
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    Quote Originally Posted by Cate&Rob View Post
    Good discussion Kim and Jim. You guys are both good at this !

    For what it’s worth . . . (a bit of an “apples and oranges” comparison) . . . My Ecoboost tows a lot more comfortably on premium fuel. I expect that this is because of better spark advance.

    Rob
    Rob,
    Your Eco boost was calibrated to run on premium fuel but can also run at a lower output on regular fuel for non-towing. Some companies will specify premium recommended where this is also the case. Any engine today that is calibrated to be on the edge of knock and even with a small amount of light knock will be the most efficient. If you towed on regular you would see and feel a difference in performance especially on grades. In the case of the 6.0L the test to run on premium is to see if excessive knock is present. If it was (test shows significant improvement), then further action at the dealer would be necessary. These systems are very complex and typically work excellent in protecting against low octane fuel and other fuel related issues.
    MidwestCamper

    Jim & Dawn
    Near Milford, Michigan
    2017 Imagine 2600RB
    2015 GMC Sierra 1500 Double Cab 4x4

  4. #24
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    Quote Originally Posted by Chiefblueman View Post
    Knock sensors working with ECUs in modern vehicles all but eliminate audible knock. When knock is detected via piezo knock sensors the ECU pulls timing back to quell knocking. This also can result in less power produced. Running a quality top tier premium gas should allow your engine to use more advanced timing and could result in better power. The higher octane fuel should reduce knock. If an engine is designed to run on regular, running premium generally will have no effect except that on your pocket book. Using high octane fuel which has a slower burn rate or flame front without advancing timing, timing curve and/or increasing compression ratio is ineffectual. This is why some engines today have dual power ratings, one on regular gas, the other on premium. I doubt the GM 6.0 is one of them.
    My guess is the additional nearly 1.5k lb curb weight difference would hamper performance between two engines of similar power ratings. 100 lbs will increase 1/4 mile acceleration by about .1 sec or about 1.5 seconds for 1500 lbs, a considerable amount. I would also surmise the tires and wheels on the 2500 have more rotational mass which can have a perceivable effect on performance. Gravity, weight and mass all affect performance.

    You've purchased a larger, heavier vehicle with a heavier drive train having more rotational mass requiring more power to spin it and using an engine with similar power ratings. For comparison, add about 2k lbs to your 1500 5.3 towing set up and report back. I suspect there is little wrong with your truck.
    If there is/was knocking, I have not heard it. I intend to try premium next time I need fuel but it takes me a while to empty a 36 gallon tank that is currently near full. I was also wondering about possible computer updates. I read something a while ago about a choice of setting the computer to optimize for mileage or power, but that may have been with regard to a diesel.

  5. #25
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    Quote Originally Posted by saguido View Post
    If there is/was knocking, I have not heard it. I intend to try premium next time I need fuel but it takes me a while to empty a 36 gallon tank that is currently near full. I was also wondering about possible computer updates. I read something a while ago about a choice of setting the computer to optimize for mileage or power, but that may have been with regard to a diesel.
    I guess I forgot to mention that if the knock/retard system is working properly you will likely not hear any knock or ping, whether caused by preignition or detonation. The system is there to prevent possible engine damage from improper or uncontrolled burn.

    I agree with Midwest Jim, try some premium fuel and see if that makes a difference. Take it to a dealer and have the ECU checked out. GM isn't going to give you a "power" setting but will make sure the ECU has the latest update and is functioning properly.

  6. #26
    Seasoned Camper
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    I can tell you from experience, for I have a 6.0 in a 2500. It will pull your load, don't worry about what gear you are in, the 2500 trans is geared much different and also the rear end is geared different! I can promise you the 2500 will out pull the 1500 with 5.3 engine! The 2500 6.0 is bullet proof also! You can hold it to the floor all day and it will keep on pulling! This is why GM stayed with this engine for so long! Many work trucks that are being abused in the field and dogging this engine and it keeps on running well into the 200,000's range!

  7. #27
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    Your post is encouraging and I am beginning to think that way also. I have a trip this weekend that is mostly interstate. It should be interesting.

  8. #28
    Seasoned Camper
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    Your trailer only weighs 800 lb more than my trailer, and I can run 60 mph up Chattanooga Mountain without trouble. I would say anything under 10,000 lb you will be fine with the 6.0. They are rated for 14,000 with a Fifth Wheel, but I would want a little more power for that kind of weight in the mountains. But, like I say, they will down shift quicker just because of the way they are geared, but keep the RPM's up with the way they are geared and they will pull very well! The 6.0 has a very flat torque curve.

  9. #29
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    Last weekend I ran about a 250 mile trip down I79 and Rt 422 in PA. I had about 1/4 tank of 87 octane in the tank when I filled up with 93 octane BP gas. Mileage actually dropped off about from around 9.5MPG to 8.5MPG, running 60-65 MPH. I filled up after the trip with 93 and the mileage is still down about 1-1.5MPG from the 87 octane gas. I had also replaced the stock air filter with a K&N. Was hoping to see improvement but I am honestly not seeing it....yet. I intend to burn through at least another tank to give it a good look, but I'm really surprised I didn't see an improvement in the numbers.

  10. #30
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    Quote Originally Posted by saguido View Post
    Last weekend I ran about a 250 mile trip down I79 and Rt 422 in PA. I had about 1/4 tank of 87 octane in the tank when I filled up with 93 octane BP gas. Mileage actually dropped off about from around 9.5MPG to 8.5MPG, running 60-65 MPH. I filled up after the trip with 93 and the mileage is still down about 1-1.5MPG from the 87 octane gas. I had also replaced the stock air filter with a K&N. Was hoping to see improvement but I am honestly not seeing it....yet. I intend to burn through at least another tank to give it a good look, but I'm really surprised I didn't see an improvement in the numbers.
    Saguido,

    What this is telling you is that you have not had any knock issues with your engine. Premium fuel has a slower burn rate than regular grade so with no knock being present, there could be some reduction in fuel economy. Had knock been present and learned in (spark reduction) you would have seen an increase in fuel economy with premium. The K&N filter however can be an issue. The oil from such filters can contaminate your mass air flow sensor and will not help with any part throttle performance anyway. Has the K&N just been installed the entire time or recently installed?
    Jim
    MidwestCamper

    Jim & Dawn
    Near Milford, Michigan
    2017 Imagine 2600RB
    2015 GMC Sierra 1500 Double Cab 4x4

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