JCHAG
Calling BS since 1999
I wanted to share my observations and see if anyone had any insight or an opinion on the possible cause of my MPG discrepancy. *Spoiler* - My concerns do not pertain to the average MPG stats displayed by the MID. I have on occasion seen mine be spot on accurate, and at other times be off by over 3MPG. Because of this, I do not keep track of what the MID says, I calculate each fill up by hand.
I own two 2013 Sonics, both manual hatchback turbos. One is an LTZ with sunroof and one is an LT with Mylink. Both have about 2000 miles each, and the average hand calculated MPGs are:
Cyber Gray LTZ, 1946 miles, 30.6 MPG
Summit White LT, 2192 miles, 33.7 MPG
My driving style and tire pressure are exactly the same on both cars. The only differences that I can think of between the two is that I have run the AC or front windshield defrost about twice as much while driving the LT, and I have had a passenger or two a couple of times in the LT, and never in the LTZ. The LT has only been run on 87 octane gas, and I have filled up the LTZ from empty 3 times in the LTZ using 93 octane. For what it's worth, I generally see a 3MPG increase when using 93, but that has nothing to do with my concern today because I'm comparing lifetime averages on both cars.
I am at a loss for what might be causing the LT to be more fuel efficient, when it occasionally has to lug around 200-350 extra pounds of human cargo, and has its engine working harder with twice as much use of the AC and defroster.
I realize the LTZ is heavier than the LT with its larger wheels and tires, fog lights, seat heater elements, and extra letter in the emblem, but is this weight (along with the added weight of the sunroof and its components) so significant that it should yield at least 3MPG difference on average?
Im also curious about how wheel and tire size can impact the observed speed of the vehicle and if this has an impact on observed miles traveled in the Sonic. In my experience with previous vehicles, changing the tire size always affected the speedometer. For example, it I set my cruise control at 60MPH, but my portable GPS says I'm actually traveling at 57MPH, after 60 minutes my odometer would have advanced 60 miles, not 57. In addition to making my car reflect more miles on the odometer than it actually had, It also made it impossible to calculate my fuel economy accurately because the speed differential was non linear. In the Sonic, is the speedometer calibrated for the wheels and tires installed on it at the factory? Is it possible that a 15 inch wheel equipped Sonic LT is traveling slower than the speed reflected on the speedometer thus making the odometer reading inflated resulting on better calculated MPGs? Or a 17 inch wheel equipped Sonic travels slower than reflected on the speedo meaning less than actual miles on the odo resulting in lower MPGs? To confuse the matter further, is it possible than an odometer will reflect true miles traveled even if the speedometer is lying, or does the odometer rely only on the speedometer to calculate it's reading?
I own two 2013 Sonics, both manual hatchback turbos. One is an LTZ with sunroof and one is an LT with Mylink. Both have about 2000 miles each, and the average hand calculated MPGs are:
Cyber Gray LTZ, 1946 miles, 30.6 MPG
Summit White LT, 2192 miles, 33.7 MPG
My driving style and tire pressure are exactly the same on both cars. The only differences that I can think of between the two is that I have run the AC or front windshield defrost about twice as much while driving the LT, and I have had a passenger or two a couple of times in the LT, and never in the LTZ. The LT has only been run on 87 octane gas, and I have filled up the LTZ from empty 3 times in the LTZ using 93 octane. For what it's worth, I generally see a 3MPG increase when using 93, but that has nothing to do with my concern today because I'm comparing lifetime averages on both cars.
I am at a loss for what might be causing the LT to be more fuel efficient, when it occasionally has to lug around 200-350 extra pounds of human cargo, and has its engine working harder with twice as much use of the AC and defroster.
I realize the LTZ is heavier than the LT with its larger wheels and tires, fog lights, seat heater elements, and extra letter in the emblem, but is this weight (along with the added weight of the sunroof and its components) so significant that it should yield at least 3MPG difference on average?
Im also curious about how wheel and tire size can impact the observed speed of the vehicle and if this has an impact on observed miles traveled in the Sonic. In my experience with previous vehicles, changing the tire size always affected the speedometer. For example, it I set my cruise control at 60MPH, but my portable GPS says I'm actually traveling at 57MPH, after 60 minutes my odometer would have advanced 60 miles, not 57. In addition to making my car reflect more miles on the odometer than it actually had, It also made it impossible to calculate my fuel economy accurately because the speed differential was non linear. In the Sonic, is the speedometer calibrated for the wheels and tires installed on it at the factory? Is it possible that a 15 inch wheel equipped Sonic LT is traveling slower than the speed reflected on the speedometer thus making the odometer reading inflated resulting on better calculated MPGs? Or a 17 inch wheel equipped Sonic travels slower than reflected on the speedo meaning less than actual miles on the odo resulting in lower MPGs? To confuse the matter further, is it possible than an odometer will reflect true miles traveled even if the speedometer is lying, or does the odometer rely only on the speedometer to calculate it's reading?
