2015 Duramax Fuel excessive fuel consumption

2015 Duramax excessive fuel consumption

Good Morning everyone. We have a '15 GMC 3500 Duramax. I had a full tank when I left the house and started driving to work, I get about halfway here and realize I am down to less then 3/4 of a tank. The truck burned somewhere around 8-10 gallons of fuel in about 20 miles. I stopped/pulled over to look under the hood and under the truck. It doesn't look like it's leaking any where. I flipped the switch on my aux tank and filled the truck back up. Gauge reads full. I get to my office and it's already down to 3/4 of a tank. Again, it doesn't look like it's leaking out anywhere. You can literally watch the gauge move. This seems crazy. Do I have some sort of Regen problem, that it's burning that much fuel in such a short time? Been looking around on other forums/google and cant seem to find my exact problem. Anyone have this problem or have an explanation. Thank you....

I would think if it is burning that much fuel you would see alot of black smoke.

dave10a said:

I would think if it is burning that much fuel you would see alot of black smoke.

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I'd agree. It would be all over the tip and down the side of the truck. But everything is looks normal.

I know on the older DMax engines if an injector was bad it would leak diesel into the crankcase and make oil as they would say. Check your oil level and see if its high. Keep in mind that if this is happening the oil will be diluted and may be hard to see on the dip stick. And, like I said, this may not even apply to the newer engines. I had an 03 and went through 3 sets of injectors and the second set leaked into the crankcase.

On another note, the inside of the motor was squeaky clean

Check to see if it is "making" oil. My bet is that it is. If its not leaking fuel, and its not burning it, it is retaining it.

farside291 said:

I know on the older DMax engines if an injector was bad it would leak diesel into the crankcase and make oil as they would say. Check your oil level and see if its high. Keep in mind that if this is happening the oil will be diluted and may be hard to see on the dip stick. And, like I said, this may not even apply to the newer engines. I had an 03 and went through 3 sets of injectors and the second set leaked into the crankcase.

On another note, the inside of the motor was squeaky clean

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I plan on checking that at lunch, just haven't had a few minutes to go out there.

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Shortest Straw said:

Check to see if it is "making" oil. My bet is that it is. If its not leaking fuel, and its not burning it, it is retaining it.

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How much could the crankcase possibly retain? I'd say by the time i got to work, I'd burned somewhere around 15 gallons of diesel, according to the gauge (if it's reading correctly). My other thought was it might be reading incorrectly, but when I transferred fuel from my aux to the the main tank, the gauge read fine, and showed the tank being filled up. This is all very puzzling.

It is possible that it is making oil and the dipstick will tell you that along with the "paper towel" test. Put a drop of oil from the dipstick on a paper towel and give it a few minutes. If you have an oil spot with a fainter "halo" around it, the halo is fuel. There are a number of "signs" with bad injectors and one is "hazing" from the exhaust at idle. If you have white smoke at idle, you may have an injector issue. A shop or even some parts stores can read the injectors. That is not a true test because return rates need to be tested also but if you have one or more at + or - 4 at idle and + or - 6 in drive with the foot on the brake you may have an injector issue. All diesels can have this problem but some early Duramax's were more likely, mainly the LB7, which yours is not.

The other possibility is the gauge so before you panic about injectors you might consider having the gauge checked and that can be tested with most equipment in a shop or dealer. My Edge will give me fuel tank measurement and injector readings.

A search of the Internet on Duramax and bad injectors will bring up a day's worth of reading material.

Agree with checking your motor oil for diesel.If you were dumping this much fuel into your exhaust system from a faulty regen,you would not doubt here the hot exhaust making an exploding sound like it’s back firing.
I had this happen to my Ford diesel,faulty regen cycle and fuel was dumped into hot exhaust causing fuel to explode in the hot exhaust.
As soon as possible check for diluted motor oil and if so ,do not drive in this state,this will tear your pistons apart and Diesel engines are expensive.
Keep us posted as to your findings.

rhodies1 said:

Agree with checking your motor oil for diesel.If you were dumping this much fuel into your exhaust system from a faulty regen,you would not doubt here the hot exhaust making an exploding sound like it’s back firing.
I had this happen to my Ford diesel,faulty regen cycle and fuel was dumped into hot exhaust causing fuel to explode in the hot exhaust.
As soon as possible check for diluted motor oil and if so ,do not drive in this state,this will tear your pistons apart and Diesel engines are expensive.
Keep us posted as to your findings.

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I sure do appreciate everyone's thoughts, Thank you. I just checked the oil, and it's right on the money, level wise. Color was good (dark brown) and the dipstick was bone dry above the oil level marks. I did what Lynn1130 suggested with letting a drop hit the paper towel to look for any "halo" but i didn't see anything. I'm going to stop and get more diesel on the way home to see if it is indeed using as much fuel as its showing on the gauge. That should help narrow it down even more....

Just a thought... It may be stuck in a regen cycle

Re: 2015 Duramax excessive fuel consumption

Have the fuel tank float arm and sender checked.


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billyjoeraybob said:

Just a thought... It may be stuck in a regen cycle

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This has crossed my mind as well. Makes sense...

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JohnDar said:

Have the fuel tank float arm and sender checked.


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Yes, exactly. Im going to get some fuel on my way home, which should help narrow it down more.

Just a thought... It may be stuck in a regen cycle

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Possible, and if so you will see the RPM higher than normal at idle and it will have a 'burning rubber" smell. But that would still be a bunch of fuel usage even for regen. I still like the faulty gauge idea.

If fuel is getting into the engine oil, you will be able to smell diesel fuel on the dip stick. Also if you are getting that much into the crankcase your oil pressure will be much lower. If so you best get the problem fixed sooner than ASAP.

CoveredWagon said:

If fuel is getting into the engine oil, you will be able to smell diesel fuel on the dip stick. Also if you are getting that much into the crankcase your oil pressure will be much lower. If so you best get the problem fixed sooner than ASAP.

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I checked the oil, it's was dead on. And there didn't seem to be a drop of fuel on the dipstick. After much discussion with others here, i am hoping its float, sensor, or something along those lines. I cant imagine something major with only 27k miles. But who knows....

You know, its got 27K, bring it back to the dealer and let them fix it.

Are you able to monitor your def level? My ford only tells me when it is good or under half. I know not everyone believes in getting a monitor but I do. My Edge showed me when our pickup was stuck in regen last year. I monitor two different egt sensors and when the exhaust temp holds at about 600 plus degrees higher than the turbo's=regen.

My Edge showed me when our pickup was stuck in regen last year.

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I have the Edge also and it does give you some advantages over the info from the DIC but it is also pretty easy, at least with the Chevy, to tell when it is is regenerating. Your idle is about 500 RPM higher than normal idle. For someone who has a new vehicle some of these indicators are not "out of the ordinary" to them so they don't key on them. If you have had a vehicle for awhile you notice, for instance, when the idle jumps 500-600 RPM, your exhaust gas temps go up and the truck smells different, I know it is in regen.

The OP pretty much cleared up the fuel in oil question and without some hazing and fuel smell in the exhaust, injectors issues are pretty much out. My 04 always had a slight diesel smell in the exhaust but then it did not have any emissions equipment on it. It was before all that garbage was required. When I had injector issues, and it happened twice in 110K miles, it hazed and smell badly of diesel. It did not make oil, but it did use oil and it never did that when it was running correctly. My 14 has NO diesel smell anywhere except if I happen to spill a little fuel when filling.

With the low mileage that the OP has, I would be very surprised if he had injector issues. The newer diesels are pretty much free of injector issues.

My Duramax is a couple years older, but my fuel gauge is doing the same thing. It's the sender. I finally got a code telling me that. However, I tried something that sounds like snake oil but it worked. I dumped a bottle of diesel injector cleaner in the tank. This actually fixed the problem. I used Stanadyne Diesel injector cleaner.

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DirtyMax88 said:

I checked the oil, it's was dead on. And there didn't seem to be a drop of fuel on the dipstick. After much discussion with others here, i am hoping its float, sensor, or something along those lines. I cant imagine something major with only 27k miles. But who knows....

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How does the oil pressure compared to before the problem? If it’s same o same o then I’m guessing you aren’t losing the fuel into the crankcase.