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I just did my third fill up, mileage dropped 1 MPG, and the DIC was way off, like 4 MPG off. And this with a 180 mile trip on rural roads, where the DIC indicated 42-43 MPG. I wonder if my last tank I didn't fill the tank the same. Do you guys fill til it clicks off, or keep trying to fill to the top? I usually fill on the slowest setting so I can check oil and wash windows, without worrying about fuel splashing out when it gets near the top. Mileage won't be accurate if I can't fill it the same each time.
 

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The best bet is to fill the tank until the pump shuts off, and then stop there. There isn't any practical way to fill any automotive to the same exact, precise level every time. Just let the combination of fill ups average themselves out.
 

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Couple things.

When the pump shuts off on its own, don't continue to fill. That's horrible for your EVAP system and will cause problems. Canister becomes saturated, tank pressures get messed up, fuel trims go out of whack, not worth ruining all that over filling your tank to the next whole dollar.

The DIC is always optimistic by 5-10%, assuming the DFCO(decel fuel cut-off) values are a little too high for averaging. We all have that problem initially. Somehow though, it seems to gradually start to fall in place as time goes on, you'll see.
 

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Just fill to the first click no need to go above that. I take it from your join date of April this year, you just bought your car. If so give it time to break in. MPG will improve. I have 24000 mi on my car and my LS is now averaging @30 mainly city driving. When I first bought my car I seemed kinda disappointed that I wasn't getting better mileage but it has definitely improved over time. Don't watch the MPG like the stock market; or you will drive yourself crazy. Time heals all MPG unless it is getting progressively worse but a MPG or 2 don't worry.
 

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I fill until it clicks, and just go to the next round number. The DIC has never been off by more than 2 mpg, but my last 3 tanks have been very accurate. It seems to be improving. There are some people that are reporting inaccurate readings, but I would not say that most people are finding it inaccurate. My Traverse and Malibu are always 100% accurate, and my Cruze seems to be getting there.
 

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My DIC's fuel consumed estimate is improving, but it is still slightly optimistic.
 

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"ONE CLICK" and done! So, when the gas pump stops, that's *it," don't try to sqeeze "in" anymore.

And, always use the "lowest/slowest" pump fill setting.

If you can't follow the above guidelines, then you seemingly are not really interested in obtaining (reasonably) accurate MPG numbers.
 

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23000 miles since December and my DIC is still consistently optimistic by 10%. I fill to the first click, wait 30 seconds or so, and can get another 1/3 to 1/2 gallon in until it clicks again. I guess the fuel needs to "settle" (for lack of a better word). Solves the "one hash below full" issue on the fuel gauge, too - which is an Eco Manual specific thing, I think.

I have an Eco manual, so grossly overfilling is less of an issue than the other models - we can squeeze another 3 gallons in the tank before we have to worry about that.
 

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Did GM do the same thing Chrysler did on my 1995 Jeep Wrangler? There was a 21 gallon tank and a 15 gallon tank. The difference was the 15 gallon tank had a longer fill and vent tube so more air is trapped in the tank and cannot escape. Thus reducing the fill capacity. People were pulling the fill tube cutting off the extra vent tubing to get the 21 gallon tank.
 

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Did GM do the same thing Chrysler did on my 1995 Jeep Wrangler? There was a 21 gallon tank and a 15 gallon tank. The difference was the 15 gallon tank had a longer fill and vent tube so more air is trapped in the tank and cannot escape. Thus reducing the fill capacity. People were pulling the fill tube cutting off the extra vent tubing to get the 21 gallon tank.
...basically (but, not exactly) yes.
 

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Did GM do the same thing Chrysler did on my 1995 Jeep Wrangler? There was a 21 gallon tank and a 15 gallon tank. The difference was the 15 gallon tank had a longer fill and vent tube so more air is trapped in the tank and cannot escape. Thus reducing the fill capacity. People were pulling the fill tube cutting off the extra vent tubing to get the 21 gallon tank.
There was quite the discussion about this a few months ago. Apparently, it's the vent close-off valve attached to the fuel pump. A bit more difficult a modification, as it requires one to drop the tank and change the fuel pump.
 

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My brand new Eco's first tank claimed 26.5 mpg all city driving with me putting my foot into the accelerator a few times. Sounds low by some of the figures in this thread but it's a 30% city mpg increase over the car I traded. It's an Eco automatic and I would be thrilled if it never drops below 25mpg but I'm hoping it even gets better. Thaking a trip mid September and anxiously awaiting great road mpg.
 
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