# Diesel mpg dropped to 30 mpg graph



## GMMillwright (Mar 5, 2011)

I think the fuel economy range (vertical axis on the right of screen) is automatic. If your economy was higher, the range would adjust accordingly. Try driving on the highway for 20 - 30 miles. Economy should go up, and the economy range should adjust itself.


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## Maverick4052003 (May 10, 2016)

Ya I've done that accualy I drove to PA over the weekend best I could get was 38 mpg. Cruze been like this now for over a month I miss the 50mpg.


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## Maverick4052003 (May 10, 2016)

This is my normal 30 mile commute from home to work today. I didn't get 30 mpg driving to work I used to get over 50 and would only have to fill up once every 9-10 work days.


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## diesel (Jun 8, 2013)

I moved this to the diesel section. You are likely seeing a DPF regen happen. It will lower the fuel economy significantly for a few miles.


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## Maverick4052003 (May 10, 2016)

OK I'll try some dpf cleaner from autozone?


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## Maverick4052003 (May 10, 2016)

This is been going on for the last few thousand miles my mpg had dropped to half what I used to get if that


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## silvertank (May 26, 2015)

Run a cleaner thru it mine does it whenever something major changes trans fluid change it did it the about 200 miles then i changed the fuel filter and same result, put a cleaner thru the tank should go back up


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## IndyDiesel (May 24, 2015)

How many miles on the car? I wouldn't add any cleaner to it. Yikes. Have you changed your fuel filter?


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## Maverick4052003 (May 10, 2016)

I didn't change the filter or add any cleaner it has 36,xxx miles. Maybe this weekend I'll try changing the fuel filter .


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## diesel (Jun 8, 2013)

Maverick4052003 said:


> OK I'll try some dpf cleaner from autozone?


No!! There is no such thing. (Well there is, but it's supposed to be squirted through the DPF after you've removed it. Not a viable option in your case, IMO. Nor is it necessary.)



Maverick4052003 said:


> This is been going on for the last few thousand miles my mpg had dropped to half what I used to get if that


Winter fuel and colder temperatures will drop the MPG noticeably in the diesels. See if it picks up as warmer weather happens. If not, a trip to the dealer may be in order. 



silvertank said:


> Run a cleaner thru it mine does it whenever something major changes trans fluid change it did it the about 200 miles then i changed the fuel filter and same result, put a cleaner thru the tank should go back up


Nobody should use a DPF cleaner. Especially don't put it in your fuel tank. All sorts of havoc is sure to ensue.


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## ChevyGuy (Dec 13, 2014)

I doubt if dealers will take a MPG issue seriously, and none under warranty/no charge. (If they do find something then it will be free, but if they find nothing, you'll have to pay for them to look at it.) Too many variables - and far too many bad drivers who want to blame the car. I can't say as I blame dealer.

But for kicks and grins, take a look at How Many Under-tightened Diesel Intake Clamps.


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## Maverick4052003 (May 10, 2016)

What about the royal purple injector cleaner


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## diesel (Jun 8, 2013)

Maverick4052003 said:


> What about the royal purple injector cleaner


That's a whole different ballgame. That appears to be a fuel additive. DPF cleaner is not a fuel additive.

There are widely differing opinions on fuel additives on this forum. I, for one, have 167K miles on my diesel, and the only thing that' ever gone into the tank is... diesel. it still runs like the day I drove it off the lot brand new.


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## Maverick4052003 (May 10, 2016)

I'll change the fuel filter and see if that changes anything


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## boraz (Aug 29, 2013)

diesel said:


> Winter fuel and colder temperatures will drop the MPG noticeably in the diesels.


my mpgs are same year round

same route year round


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## diesel (Jun 8, 2013)

boraz said:


> my mpgs are same year round
> 
> same route year round


Isn't it always winter in Canada, though?


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## Cruz15 (Mar 17, 2016)

My mileage has dropped drastically as well and its warmed up dramatically.
My instant mileage has some wonky consistent rise and fall that it never had before.


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## CruzeDan (May 17, 2015)

My mileage has been terrible (relatively to my normal performance) as of late. Got a CEL two days ago for the O2 sensor. Fixed it today, mileage seems to be much better. Cause and effect? To early to tell so far.


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## Maverick4052003 (May 10, 2016)

My 2014 diesel cruze milage is crap


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## Maverick4052003 (May 10, 2016)

That's with the royal purple cleaner and I've orderd the fuel filter


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## diesel (Jun 8, 2013)

Maverick4052003 said:


> My 2014 diesel cruze milage is crap


OK, I just noticed something that may be significant. On that same graph, my upper number is 50 not 30 like on yours. have you calculated by hand? I am willing to wager your MPG is higher than you think...

If you look at your very first post, the first one you posted with 8K miles on it shows 50 at the number at the top of the graph and the second one shows 30. have you had any software updates done that could affect the DIC? 

Try filling up (preferably to the rim of the filler next, so you know you have exactly the same amount of fuel when you refill it the next time - it takes a few minutes due to the foam) and then manually calculating.


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## Maverick4052003 (May 10, 2016)

I'm doing that now an the updates I haven't done any that I know of the cruze used to get better milage showing 50 mph at 30,000 miles this changed. I'm sure I know it's eating fuel economy I'm going to the pump once a week when it was once about every 10-14 days. The car eco meter used to ride in it at a healthy 70 mph 50mpg all day high way that's all went to ****. In changing fuel filter that don't work then in trading it in.


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## obermd (Mar 3, 2012)

Have you talked to your dealer about this. This is a 40% reduction in fuel economy, which should be sufficient to get a dealership to look at the car.


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## boraz (Aug 29, 2013)

diesel said:


> OK, I just noticed something that may be significant. On that same graph, my upper number is 50 not 30 like on yours.


thats why he made the thread


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## diesel (Jun 8, 2013)

boraz said:


> thats why he made the thread


My point is that I think the "50" is a fixed number. Even when I did my winter experiment to try to get under 10 MPG, my top number was still 50. It has always been 50, regardless of the average. I am thinking the "30" isn't really "30". I hear what he's saying about filling up more often, but I still think an actual manual consumption test is in order. I think the "30" is a bug. 

Hope that makes sense! I tried to find the pic I made as a sample of what I am saying (back a couple winters ago), but I can't locate it.


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## justin13703 (May 2, 2016)

diesel said:


> My point is that I think the "50" is a fixed number. Even when I did my winter experiment to try to get under 10 MPG, my top number was still 50. It has always been 50, regardless of the average. I am thinking the "30" isn't really "30". I hear what he's saying about filling up more often, but I still think an actual manual consumption test is in order. I think the "30" is a bug.
> 
> Hope that makes sense! I tried to find the pic I made as a sample of what I am saying (back a couple winters ago), but I can't locate it.


Mine changes back and forth between 50 and 30 too depending on what the mileage was for the time of the graph.


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## diesel (Jun 8, 2013)

Here is what I was talking about. I finally found that picture from my "see how low I can get my MPG" experiment. I managed to get it down to 10 MPG for 25 miles, but you can clearly see the upper number on the axis of the graph is still 50.


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## putercents (Apr 1, 2016)

diesel said:


> Isn't it always winter in Canada, though?


 EH? you making fun of the fact we all live in igloos? Americans are just lucky that we are not very good firebugs or your White House would be an ash pile!! lol


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## Cruzator (Dec 31, 2014)

I've been looking for this thread for a while, just to convince me that I'm not loosing my mind. My car has always had 50 as the upper number on the right side of the economy trend graph. A few months ago, my battery went dead and when I got it started again, I noticed the upper number was 30 MPG. I didn't think much about it and thought it would change. I have driven for a couple of months now with fuel economy between 45 and 49 MPG (calculated) and showing 46 MPG on my trip average and also the 500 mile averages, with 25 and 50 mile averages in the 70's (due to my long down hill decent from the mountains every day). The number on the right has never gone back to 50 MPG, although the graph bars appear to be accurate with the 50 MPG reading. I have tried resetting it, and it still stays on 30. Maybe I should unhook the battery again. Does anybody have any ideas on how to get this back to 50 on the display? Not a big deal, but I would kind of like it to be correct.


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## Rivergoer (Mar 30, 2017)

Cruzator said:


> I've been looking for this thread for a while, just to convince me that I'm not loosing my mind. My car has always had 50 as the upper number on the right side of the economy trend graph. A few months ago, my battery went dead and when I got it started again, I noticed the upper number was 30 MPG. I didn't think much about it and thought it would change. I have driven for a couple of months now with fuel economy between 45 and 49 MPG (calculated) and showing 46 MPG on my trip average and also the 500 mile averages, with 25 and 50 mile averages in the 70's (due to my long down hill decent from the mountains every day). The number on the right has never gone back to 50 MPG, although the graph bars appear to be accurate with the 50 MPG reading. I have tried resetting it, and it still stays on 30. Maybe I should unhook the battery again. Does anybody have any ideas on how to get this back to 50 on the display? Not a big deal, but I would kind of like it to be correct.


This original thread took a lot of detours around the OP's point, which is exactly what you're reporting...the Y axis is now showing 30 MPG instead of the normal 50 MPG. That has got to be some sort of glitch.

As @diesel pointed out with a photo a couple of posts above, his Y axis remained at 50 MPG always, even when he forced his MPG well BELOW 30 MPG for 30 miles. My '14 CTD always shows 50 MPG on the Y axis too (70K miles on the odometer).

Since your issue started after the battery went dead, it would definitely be worth a try to disconnect the battery for a minute or two then reconnect and see if it 'reboots' the DIC. 

If that fails, I'd find a dealer that will look into the issue. The Y axis should ALWAYS be 50 MPG. The Gen 1 CTD is NOT a 30 MPG car by any stretch of the imagination (unless you're lead-footing it in city traffic 7 days a week).


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## Cruzator (Dec 31, 2014)

Thanks, Rivergoer. I agree. I will give that a try.


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## Aranarth (Oct 18, 2016)

Just wanted to note, my graph is also 30miles by 30mpg. I'm pretty sure it used to be 30miles by 50mpg when I first got the car.
I wonder if the glitch is from the most recent ecu update with the NOX 1 sensor recall...

I don't use the graph anyway I use the range remaining, trip 1 and trip 2 to monitor my fuel economy over a long distance.

I also clear my fuel used and fill up to that amount each fill up.
Trip 1 is fillup to fillup and trip 2 is oil change to oil change.

I use the instant fuel ecomony and 25mile average when actually driving. 

My typical average fuel economy noted by trip 1 is 42 to 44 mpg (650 to 700miles). 
Freeway 25mile average is typically 48 to 55 mpg near the end of my 58mile one way commute.


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## Cruzator (Dec 31, 2014)

Thanks, Aranarth. I typically don't use the economy trend either and use the trip meters the same as you. FYI, mine did this long before the last ECU update, after the battery went dead. I did try unhooking the battery and hooking it back up, but nothing changed. ODD that your did the same thing.


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## Aranarth (Oct 18, 2016)

I don't remember if you mentioned it or not...
What is your fill-up fuel economy using the trip?


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## Cruzator (Dec 31, 2014)

Displayed is usually around 46, figured around 48 to 49. Just crossed over the 50 mpg best score for 500 miles.


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