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Discussion Starter · #1 · (Edited)
First - pictures from the fill up.

View attachment 5098 View attachment 5099 View attachment 5100

This tank started with a 15.3 gallon fillup with an estimated 3/4 of a gallon in the tank to start with. This means the Cruze ECO MT's total fuel capacity is ~16 gallons, despite the advertized 12.6 gallon tank, giving it the same tank as the other Cruze trims. The additional half gallon is the fill pipe.

I didn't see the fuel needle move for 250 miles. This is to be expected for a 16 gallon tank with in a car getting 47 MPG as this is how far you have to go to get the fuel level down far enough for the gage float to start moving. Once the fuel need started to move I discovered that the range at any time varied very little; 740 - 750 miles. This indicates the gas gage needle to drop linearly with the distance driven. I had suspected this but this was the first tank I actually kept an eye on the relationship between Trip A, DTE, and the needle on the gas gage.

When I filled up, I had been sitting on "Low" for DTE for about 20 miles. Since the "Low" triggered at 698 miles, this means I had about 25 miles, or about half a gallon, to empty. Given that I started at 16 gallons, this means I used 15.5 gallons of gas, for a 46 mpg tank. The DIC reported 15.1 gallons used, which is 2.5% low. Given that I drove up to Rocky Mountain National Park and back on this tank as well as 360 miles of commuting, this is actually rather accurate.

Deceleration Fuel Cutoff (DFCO) really works. When I drove up to Rocky Mountain National Park I dropped from an average of 48 MPG to 38 MPG. Coming back I made it back to over 46 MPG for the tank. My car was in DFCO most of the way back. Also, DFCO works on the Cruze ECO MT from idle to well over 3000 RPM. I discovered this using engine breaking. When the car comes out of DFCO at high RPM, there is a slight surge of power when the injectors are restarted. I had no power surges until I was close to 4000 RPM. The ECO MT will coast a long way in 6th gear, especially when approaching idle RPMs - neutral is definitely not needed to coast in this car.

The Trip Odometer MPG and the Game display appear to never show the same MPG. Obviously once the Game display starts its running average the two won't show the same. The Game display in my car always shows a lower mpg than the trip odometer.

Finally, my first click-off today was at 11.4 gallons. Given that I had about 1/2 gallon when I started filling today, that means the first click off was at 11.9 gallons, half a gallon below the vent system's guick shutoff at 12.6 gallons. Without actually seeing how the fuel pump assembly's vents are placed I would guess the gage float covers a gallon of the tank's capacity. This also correlates with the fact that from 60 miles to empty to my fill up the needle sat on or just below the empty line, explaining why the car is unable to give you a DTE when you're down to a gallon or so of fuel.

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Before anyone says that filling into the fill pipe can cause problems with the vapor recovery system, I'm aware that there is a small risk of this. When I did the previous fillup, I was trying to fill the actual tank and I stopped before the gas reached the fuel nozzle, but not by much. I wanted enough gas for my road trip as well as commute most of the following week. I definitely did not expect to hit 700+ miles on the tank. I was hoping for low 600s. Those few ECO MT owners who are getting better than 50 MPG should be able to get close to or more than 800 miles on a tank. This is by far the best range of any personal vehicle I have run across.
 

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Wow, I'll have to remember that for trying to get out to my relative's on 1 tank of gas.

And, that's amazing! Diesel-like fuel mileage on unleaded gas.
 

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Discussion Starter · #3 ·
I forgot two items. The gas was the second straight tank Shell 91 octane and the only mod I've made is to run the tires at 40 PSI cold. Personally I'd rather get higher MPG to reduce my commute costs.
 

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me likey!!!! goin into chev tomorrow to pick up a part and im gonna lay some pressure on my service manager to find out A) why the tank pretends to be smaller, and B) how to finally rectify this issue so that my full size tank easily and safely takes a full tanks worth of gas......
 

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Now we have to find the easiest way to fill the Eco's 15.6 gallon tank normally. It's only an 21 extra pounds for these 'extra' 3 gallons. Perhaps the transportation legals told Chevy that they 'do not want 750 miles' between fill ups.

I do not know how 'all the posts' for this subject area can be put together, meaning I do not know where in this forum to see responses to my previous posts. In this way I might be able to see answers to the question above: How do we fill this Cruze Eco 6M gas tank to 15.6 gallons with no restrictions or risk? Thanks.
 

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Well what if you put the filler neck from all other trims if I'm not mistaken it's smaller than all other trims .

Sent from my Droid
 

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Discussion Starter · #8 ·

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Discussion Starter · #9 ·
Now we have to find the easiest way to fill the Eco's 15.6 gallon tank normally. It's only an 21 extra pounds for these 'extra' 3 gallons. Perhaps the transportation legals told Chevy that they 'do not want 750 miles' between fill ups.

I do not know how 'all the posts' for this subject area can be put together, meaning I do not know where in this forum to see responses to my previous posts. In this way I might be able to see answers to the question above: How do we fill this Cruze Eco 6M gas tank to 15.6 gallons with no restrictions or risk? Thanks.
Very slowly. The problem is the ECO MT's fuel pump assembly was modified to change how the tank vents during fill up. By filling slowly you take advantage of that nice large vent call the fill pipe. Note - if the pump has one of those stupid accordian vapor recovery shrouds you will need to hold it back from the car's fill pipe with your hand.
 

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Increase your tire pressure to max sidewall and you will get over 50 mpg....
This will likely cause elevated tire wear at the center of the tread. I experienced this on a previous car with inflation less than 10 psi over the GM recommendation (i.e., still below the max sidewall value). I no longer go higher than 5 psi over the GM recommendation.
 

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Discussion Starter · #14 ·
This will likely cause elevated tire wear at the center of the tread. I experienced this on a previous car with inflation less than 10 psi over the GM recommendation (i.e., still below the max sidewall value). I no longer go higher than 5 psi over the GM recommendation.
This depends on the brand and model of the tire. I fully suspect that some tires will buldge in the center when running at sidewall max. They shouldn't because the max sidewall PSI is supposed to be the tested limit for all tires produced in that model. A few will fail at this pressure simply because of manufacturing defects.
 

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Thanks for the links. I'm still going to play it safe. While not the same tires, my observations were with a set that lasted over 60,000 miles. I'll be eager to see the tread depth records for the Eco tires after 20-30 thousand miles.
There are many people who think they're playing it safe, like my family friend Rachel. She even knew exactly what the tire pressure needed to be, and she was 1psi low, and that can be argued as a consequence of the colder temperature that day. Her shoulders front and rear were SCRUBBED on tires that she owned for less than half a year.

I haven't yet seen uneven tire wear in the center from "over-inflation." Most of the time, it's a lack of tire rotation. I have however seen uneven tire wear on the shoulders from under-inflation.

5,700 miles on my Eco now and you'd figure I would have noticed even a slight difference with the digital tire depth gauge that measures in increments of 1/64", but it's still completely flat across the tread.
 

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My 17s showed a max of 44psi and they were at 35 from the factory so I ran them up to 45 hot. I drive over 500 miles a week so I should be able to tell pretty soon any adverse side effects. The ride stiffened up some, but not enough to complain about.

Sent from my SAMSUNG-SGH-I997 using AutoGuide.Com Free App
 

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There are many people who think they're playing it safe, like my family friend Rachel. She even knew exactly what the tire pressure needed to be, and she was 1psi low, and that can be argued as a consequence of the colder temperature that day. Her shoulders front and rear were SCRUBBED on tires that she owned for less than half a year.

I haven't yet seen uneven tire wear in the center from "over-inflation." Most of the time, it's a lack of tire rotation. I have however seen uneven tire wear on the shoulders from under-inflation.

5,700 miles on my Eco now and you'd figure I would have noticed even a slight difference with the digital tire depth gauge that measures in increments of 1/64", but it's still completely flat across the tread.
By "playing it safe," I meant that I don't go more than 5 psi above recommended (i.e., my bogey is 40 psi). It never gets down to 35 psi or below. You're definitely right that going too low is bad news.
 

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i did the over fill trick this weekend for a road trip. gauge showed empty. first click was at 10.6gallons. after 10 long minutes i got another 5 gallons in there and it was still going in, i got tired and gave up knowing it had to be close to full. 5 gallons of wasted space...

got 580miles with the gauge at 1/8th tank. i filled it to the first click and then added in the 5 gallons i put on top of the first click before for a hand calculated 39.7 mpg. i am happy with that. 70+mph with the air on the entire time. also for the most part the cruise was set and it was hilly so there was some to be had there if i wanted to kill the cruise. best mpg so far, car only has 1900miles on it.
 
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