# Losing MPG



## jrb3 (May 17, 2017)

One thing I should have added, I only drive the car Monday thru Friday for work. I spend way too much time in it to drive on the weekends. I have a few other cars I drive.


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## snowwy66 (Nov 5, 2017)

It's winter time. Everything gets worse mileage.

Unless you live in the south.


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## oregon_rider (Jul 21, 2017)

Nice to see a high mileage cruze...

My first guess would be fuel. Where do you buy your fuel? They may have changed supplier or the supplier may have changed blend/additives.

Winter fuel is blended with diesel #1 avoid fuel gelling - it has less btu's and mileage drops. 

I would change fuel filter, the air filter, and run a couple of tanks of stanadyne performance formula additive through her to clean injectors and fprv.

Beyond that - take it to the dealer or get scanner where you can get injector balance rates.

jeff


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## jrb3 (May 17, 2017)

Thanks, about time for an oil change so when it's on the lift, I'll do the fuel filter and air filter (which I don't need the lift for). I'll start trying the additive too.
Anyone know if you can get injector balance rates from Gretio or another app?


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## Valpo Cruze (Feb 23, 2014)

15 Causes of Poor Gas Mileage (and How to Increase Your MPG)


Many factors can contribute to high fuel consumption in cars and trucks. Here are 15 reasons why you're experiencing bad gas mileage...




cartreatments.com





The attached link has several areas to check and see what might be happening. Your graph shows that it has been a steady overall decline but still putting up great numbers. Might just be time for a total tune up. The next question to ask is will it be worth it. Spending $1000 or more to regain just a couple of MPGs . . . . .


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## MRO1791 (Sep 2, 2016)

Have you cleaned the intake, throttle valve, and EGR in all those miles? If not that could well be the issue. By now it's certain to have some restrictive build-up of crud. The LUZ 2.0 engine needs a clean around 50K miles or it starts getting strange. It likely is a longer interval for the 1.6, but I'd take a look. That can cause a slow and gradual decline in MPG. Other suggestions like air a fuel filters are good ideas as well. Not to mention a winter blended fuel having some impact on MPG. So many factors can affect small changes in MPG it can be difficult to nail down a single cause, and it could be many small contributors. Your overall MPG is not too bad, but this car is capable of 50+ hwy consistently.. so it's worth looking into what might be happening.


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## Barry Allen (Apr 18, 2018)

Engines naturally age and wear out, and fuel economy decreases. 

My prior vehicle was a 2009 Hyundai Accent and it went from averaging 32-35 mpg to ending at about 28-29 mpg when I reached 115,000 miles. In that car, oil changes were Mobil 1 0W-20 done every 7,500 miles. The car used minimal oil for the first 75,000 miles (maybe 1/4 quart low at oil changes) and then steadily accelerated to where it was consuming about 3 quarts between oil changes. Had I kept the car I was going to switch to just changing the oil filter every 7,500 miles and never drain the oil (just top it off) because it was consuming enough to not matter.


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## Barry Allen (Apr 18, 2018)

Right in the middle of the chart it looks like you had one tank of fuel where it was HAMMER TIME ON THE GO PEDAL!

I did that in Montana in 2019 when returning from Seattle. I wanted to see how fast the cruise control could hold and I can confirm it will hold triple-digit speeds for the entire length of the state.


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## Cruz15 (Mar 17, 2016)

In my car if my map sensor is not clean I lose mileage guaranteed.


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## BodhiBenz1987 (Jan 13, 2018)

jrb3 said:


> Thanks, about time for an oil change so when it's on the lift, I'll do the fuel filter and air filter (which I don't need the lift for). I'll start trying the additive too.
> Anyone know if you can get injector balance rates from Gretio or another app?


I would imagine Gretio has the balance rates though I haven't looked for them yet. I can get them on my ScanGauge II as an X-Gauge. I agree with others to start with the simple stuff ... fuel filter, air filter, additive, and maybe try a different station in case the one you used changed suppliers. I had a little spell last spring/early summer where my economy was consistently down and I think it had to do with the sudden shift in supply/demand during the pandemic (stations selling winter fuel longer and maybe shifting suppliers, since less fuel was sold for a while). It did go way back up in late summer. Yours does seem to have a steady decline which suggests its more something that's building up over time. I second MRO1791's suggestion that it could be your intake, EGR, and associated bits are getting pretty built up with gunk and getting less and less airflow. Even with your relatively high mileage I would not expect actual engine wear to the point of that kind of mileage drop. My 33-year-old car with 314k miles was getting as good mileage as it ever did when I stopped driving it five years ago. It helped when I cleaned a couple decades of soot out of the intake manifold on that one!


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## phil1734 (Aug 30, 2019)

Well the graph should rule out any cyclical changes in fuel blend or ambient conditions, and I hope for all our sake 50,000 miles or two years isn't the life span of the engine internals.

But in addition to other recommendations for a bit of cleaning, there have been a handful of Gen 2 owners (both gassers and diesels) that have had sticky brake caliper pins, myself included. I believe in all cases only the front calipers were affected. If that is your case, your first sign of trouble will be uneven wear on the inside of the rotor.


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## Barry Allen (Apr 18, 2018)

phil1734 said:


> I hope for all our sake 50,000 miles or two years isn't the life span of the engine internals.


It wouldn't be the total lifespan. It could just be the start of a slow, steady decline in perfect performance until, some time in the future, it becomes unacceptable.


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## snowwy66 (Nov 5, 2017)

It'll get better in the summertime. 

I've never seen brakes be the cause in my 12 years of wrenching. Brakes would have to be dragging and heating up.


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## phil1734 (Aug 30, 2019)

snowwy66 said:


> It'll get better in the summertime.
> 
> I've never seen brakes be the cause in my 12 years of wrenching. Brakes would have to be dragging and heating up.


But he has data for two years and it has shown a steady decline at an increasing rate. Am I the only one seeing the graph that goes from Spring 2017 to late 2020? This is not a seasonal fuel-blend issue.

And how much drag do you think it would take to chip away a few MPG on one of these cars? Combined with the increased abrasiveness of some rust, do you think burning through a set of front brake pads in under 30,000 miles _might_ be indicative of a little bit of drag? Because if so, I have news for you: What a dang mess!!! Front & Rear pad & rotor...


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## snowwy66 (Nov 5, 2017)

phil1734 said:


> But he has data for two years and it has shown a steady decline at an increasing rate. Am I the only one seeing the graph that goes from Spring 2017 to late 2020? This is not a seasonal fuel-blend issue.
> 
> And how much drag do you think it would take to chip away a few MPG on one of these cars? Combined with the increased abrasiveness of some rust, do you think burning through a set of front brake pads in under 30,000 miles _might_ be indicative of a little bit of drag? Because if so, I have news for you: What a dang mess!!! Front & Rear pad & rotor...



That's not news to me. 
I turned wrenches for 12 years for a living. 

Ford Taurus chews up brakes every 20k..But they aren't dragging.


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## 6speedTi (May 18, 2018)

I recently did a highway run. I filled up to the top a a Chevron station. I drove about 300 plus miles. I can't remember exact mileage but on the return trip I topped off at the same station using the same pump the same top off method. My onboard computer put me at avg 54 mpg. My actual based on the pump readings put me at 58 mpg. I never seen it this high on the past. I've always used Shell fuel. This time I used Chevron. Was there a difference in fuel chemistry between Shell and Chevron? Florida law does not mandate for service stations to post cetane ratings. So I can only assume they are both rated at 40 cetane. Although this was a one time switch over it is possible different oil companies use different fuel chemistry and cetane ratings. Try switching brands to another major oil company and see if you get any difference in mpg's. Make sure your driving habits are similar when you compare.


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## Carminooch (Mar 23, 2018)

I’ve had issues with my intake and my egr system getting VERY choked up with soot. I noticed my fuel economy was decreasing. I would be curious to know after the miles you put on, how clogged up your egr, intake, MAP sensor, and how your MAF looks.

Have you considered looking into that? Pop off the black plastic intake pipe at the egr and have a look at the valve inside.


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## MP81 (Jul 20, 2015)

I've never found our fuel economy to increase when I clean the EGR valve and the throttle plate every ~45k miles - it just helps with smoothing out how the car runs on cold starts.

It's entirely that, slowly, over time, your foot has been going down just a touch more than it used to.

I found this to be the case with my Volt last winter - wondering why my range didn't seem to be as good as it once was (comparing winter to winter). Turns out, it's mostly with how I drive. I know that I can get where I need to and back and have tons of range left, so I am far more apt to utilize that electric torque for fun (or out of frustration) than I would have the first year or two of owning the vehicle. If I behave myself, it's right where it used to be. But that's less fun, so...


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## Barry Allen (Apr 18, 2018)

6speedTi said:


> I recently did a highway run. I filled up to the top a a Chevron station. I drove about 300 plus miles. I can't remember exact mileage but on the return trip I topped off at the same station using the same pump the same top off method. My onboard computer put me at avg 54 mpg. My actual based on the pump readings put me at 58 mpg. I never seen it this high on the past. I've always used Shell fuel. This time I used Chevron. Was there a difference in fuel chemistry between Shell and Chevron? Florida law does not mandate for service stations to post cetane ratings. So I can only assume they are both rated at 40 cetane. Although this was a one time switch over it is possible different oil companies use different fuel chemistry and cetane ratings. Try switching brands to another major oil company and see if you get any difference in mpg's. Make sure your driving habits are similar when you compare.


Having an uncle that works in the oil/chemical industry, I know Things™ about petroleum refining. I'm no PhD, but just enough knowledge to be dangerous.

Since the implementation of ULSD, diesel fuel has fairly strict product standards. It all conforms to ASTM D975 in the USA, and there are no brands or refineries that are making any "magic" diesel fuel that is better than anything else that meets the spec. The minimum cetane is 40, which is somewhat ridiculous that it hasn't been increased to help emissions, but I digress. Most diesel fuel coming out of the refinery is achieving about 44-46 cetane with base fuel properties and various additive packages blended with the different brands. Fuel blends with biodiesel can often add one or two points to the cetane number, so maybe approaching 50.


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## jrb3 (May 17, 2017)

Thanks for all of the replies. 111k, the first few oil changes were done at the dealer, I've done the maintenance since besides a bad DEF batch (WalMart brand, now I make sure I only run Blue DEF) which required a dealer visit where they drained the tank (Feb 2019). Interestingly enough, they didn't do the recall for ECM / filter at that time and it's hasn't been done. Maintenance has been oil changes (based on DIC), fuel filter changes (DIC @25% - I kind of remember reading that fuel filter calculation isn't great), antifreeze flush, air filter, cabin filter and a set of tires.

I'm still on original brakes (+50% all around), clutch, flywheel, slave, master, etc... so besides not being the most comfortable car, it's been reliable. Before anyone asks why I don't think it's comfortable, mine's an LT with leather prep package. In my opinion seats have always kind of sucked and I've always heard the Chevy struts clunk. Every front wheel drive Chevy I've owned over the last 15 years has the same clunk. Highway miles are a great thing.

I'm pretty sure it's not seasonal, it's been a steady decline from May 2017 to now. I'm going to run some additive to see if it's injectors and then when I get it on my lift to do the oil change, see if there is anything with a lot of soot. I can try a new station, but I use QT. Which brings up a new question - QT is Tier 1, which I think is a gasoline only, anyone have any idea what that means for diesel?


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## Barry Allen (Apr 18, 2018)

jrb3 said:


> I kind of remember reading that fuel filter calculation isn't great


Mine tracked right to 40,000 miles, but had thought it was calibrated to call for a change after 1,000 gallons of fuel. Maybe it's a little conservative, because it was just under 900 gallons when I was at 0% for the fuel filter change.


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## Barry Allen (Apr 18, 2018)

jrb3 said:


> QT is Tier 1, which I think is a gasoline only, anyone have any idea what that means for diesel?








TOP TIER™ Diesel Fuel Brands







www.toptiergas.com





There are only four brands listed as TOP TIER™ diesel fuel:
Costco Wholesale (select US locations)
Fast Stop (select US locations)
Fast Stop Express (select US locations)
Kirkland Signature (select US locations)

Kirkland is the house brand of Costco, so I'm unsure why it's listed as separate.

Finding Top Tier diesel fuel is hit and miss. It's labeled on the pump, but you can't really find a map of locations as far as I know. Costco lists their locations and there isn't one anywhere near me. Fast Stop (funny enough, headquartered in my current city) has a new thing that is a list of some stations - the closest one is about a 2 hour drive south of me.

Costco is certainly buying their fuel from multiple suppliers due to their geographic spread across the USA. This virtually guarantees that Top Tier diesel is an additive package just the same as the gasoline is. Costco is getting bulk deliveries of diesel fuel and the additive package is either added at the rack when the tank truck is loaded, or maybe it's poured into the underground tank when it's delivered. Additives put in the fuel blend at the rack is likely, because a metering pump just adds an injection of additive for every XXX gallons of diesel that is flowing into the tanker truck, and it's mixed on the drive to the station and mixed as it's dumped into the underground tank.

I don't know about Fast Stop, but the geographic spread of their Top Tier stations listed appears to be sporadic. It's also likely to be an additive package that's probably a choice by individual stations. Who knows what the total cost is, but maybe a couple cents per gallon?

If you want to put your own additives into whatever diesel you buy, Stanadyne is available on Amazon for less than $100 for a 12-pack case. You could pour 1/4 bottle into each tank of fuel, or even 1/2 a bottle if you want to double-dose it. The bottle treats up to 60 gallons, so 1/4 bottle is right in line with the instructions to be a little extra dose. 1/2 a bottle is certainly a good additive package if you have symptoms that call for some extra injector cleaning. I had one tank of fuel I bought from a station I thought was OK, and I had problems where the engine was shuddering at steady city cruising speeds. A bottle of Stanadyne split into two tanks of fuel cleared the problem up for me, so that's my two cents on the subject.


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## CRUISE-CRUZE (Nov 8, 2010)

If you from an optimistic perspective you are actually able to keep the same MPG!


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## jrb3 (May 17, 2017)

I just wanted to update this. I've run cleaner through it, changed the oil, but did not change the fuel filter or change fueling location.
Last 10 (I've filled up 9 times since my first post) is 48.10 / Last 20 is 47.08. Getting better, still not 50+ consistent average like when I got it, but better. I've never owned a diesel that got worse mileage then when new. As break in happens, they have all gotten better.


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## phil1734 (Aug 30, 2019)

Out of curiosity, did you ever check the backside of the rotors? It unfortunately has to be the backside, which usually means pulling off the wheel and peaking behind the backing plate back to get a glimpse. Looking through the wheels will tell you nothing.


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## Cruz15 (Mar 17, 2016)

Are you an aggressive driver? Have others called you a spirited or aggressive driver? Are you heavy? I weigh close to 300 lbs so Im no light weight.
You should clean your map sensor, or replace it at the dealer. What happens every couple months of ownership? Is there weird construction or dust storms?


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## rcruze (Mar 22, 2018)

For what it is worth...pre 100k miles I did a best of 62.5 mpg over a 50 mile stretch. Post 100k my average did seem to drop. More of a high 40's low 50's. But I assumed it was more due to the new roads I was taking to work or a few other changes (another set of tires, tire pressure etc)

Then when I got to about 130k it started going back up again. Now at almost 150k I am again averaging high 50's and climbing...


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## Barry Allen (Apr 18, 2018)

It's been my knowledge through word-of-mouth that gasoline engines tend to lose fuel economy as they age because of regular wear. In my most recent vehicle where I tracked fuel economy, that was true. I had a Hyundai Accent purchased new and the best fuel economy numbers were in the first 50k miles of ownership. After that, it never again achieved that and had a steady, slight decline all the way to about 115k when I sold the car. Over that time period, oil consumption also increased - the car went from consuming about 1/2 a quart of oil every 7,500 miles to reach a consumption of 2-3 quarts every 7,500 miles. My guess is the engine was experiencing normal wear.

I've been told that diesel engines don't wear out as quickly because of the lubrication properties of the fuel. Diesel fuel is an oil, so the fuel injected into the cylinders functions as a lubricant with the piston rings rather than in gasoline engines where the fuel is a solvent.

That may be true in the past when there wasn't so much emissions equipment that essentially feeds the engine it's own waste (soot recirculated into the intake with EGR). Newer diesel engines have oil that fills up with soot and other abrasive particles much faster than older engines where most of the soot went out the exhaust pipe. The end result is that oil changes are very important to modern diesel engines because you have to get all the trash/soot out of the engine oil by changing it on a regular basis.


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## Carminooch (Mar 23, 2018)

Hey I’m not sure if I can report a significant improvement on my MPG just yet but I removed and cleaned my plugged up MAP sensor and holy smokes it makes a big difference in the cars “peppiness”. 

I posted a new thread here just the other day showing how plugged up mine was. Consider cleaning yours out to see if it makes a difference in MPG. Super easy to do


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## jrb3 (May 17, 2017)

I just wanted to update this. 126k miles and my MPG is improving. I bought a new MAP, but have not installed it. After reading through all of the comments (thank you), I used Opti-Lube Single clean (I've used opti-lube before when I had my Dodge Cummins). I've been using their XL with every fill up. I can't remember why I didn't use Summer blend. I think I was just trying to keep my initial investment down, but it would be cheaper per fill up. I have no idea if the addititive is doing anything or not. No real way to analyze. Anyway, MPG is coming up, even with AC wide open the last couple of months. Trend is 10 fill up moving average. I don't remember what my first chart was.


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## rcruze (Mar 22, 2018)

You seeing an improvement at 126k mimics the improvements I saw right around the 130k mile mark. Imo I think the drop, then slow climb back is normal...

Now at over 150k I could make a good case that my mpg is back to "normal"


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## jrb3 (May 17, 2017)

I thought I would update. 301st fill today. Averaging 49.52 over the life of the car. Trend line is last 10 fill ups.


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## Barry Allen (Apr 18, 2018)

My car isn't doing so great lately:


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## bigsox (4 mo ago)

jrb3 said:


> I have a 2017 6 speed diesel that I bought in May of 2017. I've filled up 195 times, probably 175 of those at the same station. I drive 75 miles one way to work (150 miles a day) and hand calculate every fill up. I don't drive in stop and go traffic, it's 67 miles highway. Although when COVID shutdowns were full blown, I fought the temptation of hammer down, and drive around 75-80, tire pressures at 36-37 psi. I have a couple of miles under 111k. My cars done 189 regens, just did one today, with an average of 587 miles between. My 12 month fill up averages are like this:
> 
> 5/17 thru 4/18 - 51.51 (50 fill ups)
> 5/18 thru 4/19 - 50.36 (52 fill ups)
> ...


 its your DPF, is getting plugged. I had the same thing on my 2014 cruze diesel. around 200k KM fuel mileage was getting shitty. @ 250k KM it went into limp mode. changed out the DPF and fuel mileage went way up.


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## Barry Allen (Apr 18, 2018)

bigsox said:


> its your DPF, is getting plugged. I had the same thing on my 2014 cruze diesel. around 200k KM fuel mileage was getting shitty. @ 250k KM it went into limp mode. changed out the DPF and fuel mileage went way up.


Things like this make me wonder if I should spend the money up front to tune the engine and put in a straight pipe.


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## schmove1 (Feb 12, 2019)

I went through what I thought was the same thing. My last service I did the fuel filter, oil change, air filter, and something I hadn't really put much thought into. Tire air pressure.
I've come to find out the fuel mileage on these cars are crazy sensitive to changes in tire pressure.
My tires (newest set. 1 change from originals) are max psi of 44. 
When the tires were changed the dealer filled them to 35. Mileage hit the toilet from 54 to 47mpg.
Filled them to 38-39 and the mileage went 49.
Now they are at 42 (2 pounds under max) and the mileage is back up to 52.
Just my experience with the same commute over the last 4 years of ownership. Using cruise at 70.


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## Barry Allen (Apr 18, 2018)

I think the problem for me was the air filter. I mistakenly thought I had changed it a while ago and when looking at maintenance records it's been about 40,000 miles. The filter in the car was thoroughly dirty and I put a new one in, so will see what happens.


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