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Low MPG why?

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Old Jul 2, 2015 | 03:44 PM
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Default Low MPG why?

My vette has been giving me 15 mpg throughout the whole tank. The best I've gotten so far is 17mpg and that was a 300 mile trip. I've attached live data at idle from my obd2 scanner. Note the trims are in the negatives? Is this normal?


Thanks,
Aj
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Old Jul 2, 2015 | 08:10 PM
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Is it throwing any codes?

I usually get 16 in the city and 27 highway
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Old Jul 2, 2015 | 08:59 PM
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Originally Posted by brplatz
Is it throwing any codes?

I usually get 16 in the city and 27 highway

No codes at all.
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Old Jul 3, 2015 | 12:22 PM
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Bad batch of gas?
Running premium?
Tires properly inflated?
Using correct gear?
Heavy foot?
I get 16 in the city, in a Z, with a relatively heavy foot.
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Old Jul 3, 2015 | 02:52 PM
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We no know thing about your car. None of us are mind readers.

z06? year? mileage? auto? manual? mods? has it been tuned? Is this car new to you? if not, is this low mileage new? what did it used to get?
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Old Jul 3, 2015 | 04:45 PM
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Originally Posted by Sox-Fan
We no know thing about your car. None of us are mind readers.

z06? year? mileage? auto? manual? mods? has it been tuned? Is this car new to you? if not, is this low mileage new? what did it used to get?

2003 c5 z06, 54k miles, no mods, just bought the car, and its manual. I don't really have a heavy foot but I occasionally step on it.
I just went to Abel Chev to get the check valves fixed and some vacuum leaks. Other than that I believe its running rich because the exhaust smells but that just could be me. Sorry for the vague info in my previous post
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Old Jul 4, 2015 | 11:10 AM
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I know that you said no mods, but if it smells that bad I have to ask the obvious. Does it still have cats? 17 around town is normal. 17 on a 300 mile highway trip is not normal. And neither is a rich smell.

If you have an OBD2 reader are you O2 sensors reading right (note: this is pretty much a wild guess still)
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Old Jul 4, 2015 | 12:20 PM
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So the 17MPG for that 300 mile trip was from the DIC? Or did you calculate it the old-fashioned way? Were you using 6th gear?

My '02 C5 6-speed coupe will get 28-30 MPG on long trips and that's a manual calculation, not from the DIC. The car has a Vortec supercharger and a SuperChips tune. Around town it will get 17 MPG. On the track, maybe 8 MPG on a good day....

Wonder if you have one or more injectors dumping fuel??
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Old Jul 4, 2015 | 07:26 PM
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Originally Posted by c4cruiser
So the 17MPG for that 300 mile trip was from the DIC? Or did you calculate it the old-fashioned way? Were you using 6th gear?

My '02 C5 6-speed coupe will get 28-30 MPG on long trips and that's a manual calculation, not from the DIC. The car has a Vortec supercharger and a SuperChips tune. Around town it will get 17 MPG. On the track, maybe 8 MPG on a good day....

Wonder if you have one or more injectors dumping fuel??

I calculated it the old fashion way. I used 6th gear and was cruising at 70mph the whole way there. I'm not really sure wants going on. I posted some live data on the first post.
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