I had an oxygen sensor replaced.
Prior to that I got 20 mpg in the city for my CX7.
Now I am getting 21.5 mpg.
Could that increase be due to the replacement of the O2 sensor?
Thanks.
Yes it could. Warmer weather could also be part of it.
Only got 20MPG ? Every time ? Must be something wrong with my vehicle because I get a range from 31.4 to 35.3 and sometimes more or less than those. Also it is about time for the fuel mixture to change from cold weather to warmer .
Yes every time. I get 28 hwy when using the cruise control.
My 2009 has a 2.4 Liter turbo charged.
Sounds like your cx7 must be newer or have smaller engine
Here are the specs.
2009 Mazda CX-7 · Specs
Overview
MSRP $23,900 - $28,400 ·
Fuel economy Up to 17/23 mpg (city/highway)
Thanks for the info. Do cars get lower mpg in colder weather?
Yes they do . Which is why I suspect you are not checking your miles per gallon the proper way . Very few vehicles get the same MPG every tank and most do not exceed the city / highway rating every time.
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Your mpgs sound about right. Folks with the 2009 average 18 mpg on Fuelley:
Mazda CX-7 MPG - Actual MPG from 123 Mazda CX-7 owners (fuelly.com)
In a CX-7? A car that big gets 35mpg?
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If you do the same sort of driving, same routes and driving habits, your mpg will be fairly consistent. Not necessarily spot on but within a fairly narrow range. Mine certainly is.
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+1
While it varies a bit depending on the season, within a season my gas mileage varies very little, probably because my driving patterns and behaviors are quite consistent.
As an example, in local driving, my mileage in the winter is 23-24 mpg, but once the weather warms-up, my mileage for local driving is almost always in the 25-26 mpg range. For longer trips, no matter what the season might be, my typical mpgs are in the 27-29 range.
I said my vehicle ( I don’t have a CX7 ) . The point being that it is rare that someone gets the same MPG every time and exceeds the rating every time . Which goes back to I doubt if he is checking his MPG correctly since he asked if winter weather reduced miles per gallon.
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Oh, I see. I rarely bother to check mileage by dividing miles by gallons anymore. I just use the readout on the instrument panel. Whether it’s accurate or not isn’t important, just that the reading is consistent.
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+1
I consider the mpg readout to be a “cheap and dirty” diagnostic tool. If it took a nosedive, and if I hadn’t been in stop & go driving, that would indicate a possible problem, IMHO.
But, after doing repeated comparisons of the readout with actual paper & pencil calculations, I have confirmed that the readout is a consistent .4 mpg optimistic. That’s close enough for me.
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Sounds about dead on. I mean, when was the last time your pencil was calibrated? 
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Yes, a lot lower.
I know how to check my mpg. Been doing it over 40 yrs. Who said anything about getting the same mpg every tank? 
That’s impressive that the gauge is so accurate compared to manually calculating mpg
. 
Better than my Hyundai, which is 7% optimistic.
I stopped doing manual calculation after the first few months.
On a road trip getting a real 30 mpg it displayed ~32.
Puttering around town in the winter getting 20 mpg it displayed ~21.5.
You did by stating one number for city and one for highway and then asked if colder weather reduced mpg. If you were checking you would have a range from low to high .
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Where’d he say that?