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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)
5/19 thru 4/20 - 49.88 (53 fill ups)
5/20 thru yesterday - 47.75 (40 fill ups)

My last # look like this:
Last 10 - 45.84
Last 20 - 46.88

Any area I should be looking at, like a leak or something? Also, anyone have any idea why Gretio wouldn't up some items on the dashboard, but will when you click in to modify?
290277
 

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Discussion Starter #2
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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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2014 Cruze Diesel, 2007 Cobalt, 1981 Camaro Z28, 2017 Volt
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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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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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