Engine knock/pinging on 89 octane

[Volman197020]

I know there a bunch of threads on 5.7 octane usage, but I didn't see one specifically on this topic. I have a 2019 Bighorn Crew Cab 4x4.

I have a pretty long (250 yds or so) and steep hill at the entrance to my subdivision. I had noticed some knocking under load while going up the hill. Top speed is max 20 mph. Had been running 87 consistently (which isn't necessarily something I should have done). I ran it dry and filled up with 89. $75 given the current fuel gouging.

While going up the same hill, I still hear the knocking. In fact it seems worse.

1. Should I hear a difference immediately?
2. If not, should I run 93?

Thanks in advance for your advice.

 

[Fatherof3]

I know there a bunch of threads on 5.7 octane usage, but I didn't see one specifically on this topic. I have a 2019 Bighorn Crew Cab 4x4.

I have a pretty long (250 yds or so) and steep hill at the entrance to my subdivision. I had noticed some knocking under load while going up the hill. Top speed is max 20 mph. Had been running 87 consistently (which isn't necessarily something I should have done). I ran it dry and filled up with 89. $75 given the current fuel gouging.

While going up the same hill, I still hear the knocking. In fact it seems worse.

1. Should I hear a difference immediately?
2. If not, should I run 93?

Thanks in advance for your advice.

There shouldn't be any need to run 93 . The computer will take a little time to adjust for the different octane , I don't know how much time though . I've always ran 91 octane on my Hemis but I don't believe it's necessary .

 

[Lufty]

Volman- do you always get gas at the same station? I would maybe try a different gas station if so.
We run 91 (ethanol free) in our hemis and boat like Fatherof3. I don’t think you need 93 either but maybe that station got some bad gas. I think some or maybe all pumps now mix/blend the 87 and 93(91) to make 89 now.

 

[5thGenLoco]

89 is recommended but, 87 is acceptable. I would drive it some more and possibly change gas stations/brands before I'd worry too much.

 

[tidefan1967]

If its lugging up that hill(and yes 20 MPH in a higher gear is lugging) with MDS active I could see you getting a little spark knock. If the fuel grade change doesn't help I would suggest downshifting to a lower gear to get the RPM up a little bit and I bet that it would help tremendously. Working a gasoline engine at a low RPM like that could possibly cause some pre-ignition problems.

 

[Volman197020]

Volman- do you always get gas at the same station? I would maybe try a different gas station if so.
We run 91 (ethanol free) in our hemis and boat like Fatherof3. I don’t think you need 93 either but maybe that station got some bad gas. I think some or maybe all pumps now mix/blend the 87 and 93(91) to make 89 now.

I don't always use the same one, but the one I used this time was a Shell station. I am in TN ( therefore the "Vol" in Volman..ha). In 99% of the stations in my area the only ethanol free option is 87. I filled up with 89 containing ethanol.

 

[Volman197020]

If its lugging up that hill(and yes 20 MPH in a higher gear is lugging) with MDS active I could see you getting a little spark knock. If the fuel grade change doesn't help I would suggest downshifting to a lower gear to get the RPM up a little bit and I bet that it would help tremendously. Working a gasoline engine at a low RPM like that could possibly cause some pre-ignition problems.

I am usually in 2nd at the bottom of the hill, and depending on the weight of my right foot, it may shift to 3rd. I am assuming that when MDS is active I would see ECO on the panel (?). I have never seen my MDS kick on in any gear under 5th. It does lug a little if it shifts into 3rd near the top of the hill.

 

[tidefan1967]

The ECO light and MDS technically don’t have anything to do with one another. The ECO light just indicates that you’re driving in manner that will save gas. The only way to disable MDS is with the gear +/- buttons on the lower right part of the steering wheel.

 

[silver billet]

The ECO light and MDS technically don’t have anything to do with one another. The ECO light just indicates that you’re driving in manner that will save gas. The only way to disable MDS is with the gear +/- buttons on the lower right part of the steering wheel.

Nope; the ECO and MDS is 100% tied to eachother in 5th gens. ECO = MDS. If you disable MDS with the +/- the ECO light will never come on.

When my truck goes into MDS, 3 things happen in the same microsecond; I feel a tug, the exhaust changes, and the ECO light comes on. When MDS goes off, the exact same 3 things happen again; a tug (bigger one when it goes off), exhaust change, and ECO light goes off.

 

[brian42]

89 is recommended but, 87 is acceptable. I would drive it some more and possibly change gas stations/brands before I'd worry too much.

Top Tier is also recommended. Are you using a name brand station (Chevron, Shell, Costco, etc.) or a mom and pop (EZ-Fuel, Joey's Pit Stop, etc.)?

The ECO light and MDS technically don’t have anything to do with one another. The ECO light just indicates that you’re driving in manner that will save gas. The only way to disable MDS is with the gear +/- buttons on the lower right part of the steering wheel.

I'm not sure about previous generations (or other vehicles) but the ECO light is the MDS indicator for the DT trucks. Most trucks don't come with it activated (the ECO light) so you have to enable it in your settings.

The only ways to disable MDS (without 3rd party things like TazerDT) is the +/- gearshift buttons or Tow/Haul mode.

 

[tidefan1967]

Nope; the ECO and MDS is 100% tied to eachother in 5th gens. ECO = MDS. If you disable MDS with the +/- the ECO light will never come on.

When my truck goes into MDS, 3 things happen in the same microsecond; I feel a tug, the exhaust changes, and the ECO light comes on. When MDS goes off, the exact same 3 things happen again; a tug (bigger one when it goes off), exhaust change, and ECO light goes off.

So if I disable the ECO light then the MDS won’t engage? I’ll have to try that on the way home from work tonight. It certainly wasn’t that way with the 4th gens.

 

[brian42]

Sorry I wasn't clear: MDS is an automatic function so there's no setting to enable/disable it (otherwise tons of people would have done that already).

The setting is only for the ECO light on your dash and does not disable MDS:

uConnect (radio touch-screen) - Settings - Display - Fuel Saver Display in Cluster

I edited my previous post (#10) to be more clear.

 

[Richard320]

I would think you'd hear a difference right away. Reason: on 87 it would have detected some pinging and retarded the base timing. So with the higher octane and retarded timing, pinging should disappear.

I would try another brand/station next fillup and also try a little heavier foot going up the hill. Keeping the trans down and the RPM up should eliminate the knock.

 

[brian42]

You can also use the gear selector (+/-) to keep it in a lower gear and the revs up.

 

[silver billet]

So if I disable the ECO light then the MDS won’t engage? I’ll have to try that on the way home from work tonight. It certainly wasn’t that way with the 4th gens.

Turning off the ECO light via uconnect just turns off the light on the dash. It doesn't stop MDS from activating.

 

[tidefan1967]

Turning off the ECO light via uconnect just turns off the light on the dash. It doesn't stop MDS from activating.

So basically what I said in my first post, just an indicator that one is driving in a fuel saving mode, no connection to MDS whatsoever and I guarantee has absolutely no bearing on fuel economy whatsoever except in someone's mind. So basically, no exactly the same as in the 4th gen models.

 

[SD Rebel]

So basically what I said in my first post, just an indicator that one is driving in a fuel saving mode, no connection to MDS whatsoever and I guarantee has absolutely no bearing on fuel economy whatsoever except in someone's mind. So basically, no exactly the same as in the 4th gen models.

No, the Eco light is the indicator of MDS operation on this generation of trucks. In other words, if you activate the Eco Light (its off by default), and you see it on, it means the truck is in 4-cylinder mode.

They are just saying that turning off the indicator light on your dash has no effect it's operation. Again, it's just an indicator of MDS operation, nothing to do with controlling its function.

The only way to turn off MDS is selecting 8th gear on the gear limiter or activating Tow/Haul mode.

 

[silver billet]

So basically what I said in my first post, just an indicator that one is driving in a fuel saving mode, no connection to MDS whatsoever and I guarantee has absolutely no bearing on fuel economy whatsoever except in someone's mind. So basically, no exactly the same as in the 4th gen models.

What @SD Rebel said. The light appears under 2 conditions; 1) you've selected the option to have it show up on your dash via uconnect, and 2) the truck is in MDS at the current time. Both those conditions need to be true.

But MDS will still go on/off regardless of what the little light is doing.

Think of it like a hot engine warning light; preventing the light from turning on doesn't mean your truck won't overheat, that's independent of the light. But if you choose to display the light, then the light will go on/off depending on the temperature of your truck.

 

[theblet]

You shouldn’t get an knocking on 87 since it’s acceptable. 89 is recommended for max performance.

 

[Ramtrx]

You can turn mds off or keep from engaging either with tuner or the gear switch and put it on 8th. Also if you are pinging on any grade fuel you need to have it looked at. Mine pings like crazy with or without tune under medium to heavy throttleor different fuels. Turned out to be bad lifter. So something to think about