You state "mostly highway at less than ideal speed..." Does this mean mostly highway driving at less than 45 mph? 43-45 mph steady driving would net you the highest mpg as this is where the trans upshifts to 5th (assuming the automatic). Speeds above the mid-40s incur more wind drag and therefore lower mpg.First two fill-ups.
Miles - Fill-up - MPG
295 - 10.2 - ~29 (mixed road conditions where I'd avg ~21 with my previous car V6+mods)
218 - 09.1 - ~24 (mostly highway at less than ideal speed and a NY traffic jam+detour)
^^ Hmm...notice anything strange about those numbers? 29 is too high for mixed and 24 is way to low for mostly highway. I can't believe I'm the only person who complains about the fuel mileage being impossible to accurately calculate in this car.
Exactly.There may be something in the design of the filler neck that causes some pumps to shut off sooner and others later, but if you just average your mpg over many tanks it minimizes the possible error.
There may be something in the design of the filler neck that causes some pumps to shut off sooner and others later, but if you just average your mpg over many tanks it minimizes the possible error.
Exactly.
The trip computer in my 2012 has been pessimistic every tank except one (through 1,600 miles); usually it reads low by 0.6-1.0 mpg.Brought over my Scangauge2 from my other car, which btw threw a CEL at first. Had to set the engine size properly and reconnect. Will have to calibrate it with the next two fill-ups or so but look forward to observing the car’s fuel consumption behavior.
The opposite. Let's just say this was NJ turnpike and I'm cruising at 3500-4000 RPM in a manual (evil)You state "mostly highway at less than ideal speed..." Does this mean mostly highway driving at less than 45 mph? 43-45 mph steady driving would net you the highest mpg as this is where the trans upshifts to 5th (assuming the automatic). Speeds above the mid-40s incur more wind drag and therefore lower mpg.
I agree. There are many conditions that affect observed MPG. Just posting for reference. I've rented the auto Mz5 on 3 week-long occasions and avg <20 fun-filled MPGs (nana)Another thought...due to differences in tank fill-ups from different gas stations, different pumps (shut-off mechanisms), and differences in your fill-up techniques for the two fill-ups, a one gallon shift from tank #2 to tank #1 would result in higher mpg for tank #2. It's very difficult to accurately compare just two tanks of gas.
Is there an option to calibrate the OEM trip/MPG computer? How would you adjust for aftermarket wheels –which I think you have. Maybe I’m a glass half empty kinda guy but I rather computer be pessimistic than optimistic.The trip computer in my 2012 has been pessimistic every tank except one (through 1,600 miles); usually it reads low by 0.6-1.0 mpg.
Different tire sizes won't affect the trip computer, per se, as the computer calculates distance based on the number of axle/wheel revolutions, not the actual distance traveled. The upshot is:Is there an option to calibrate the OEM trip/MPG computer? How would you adjust for aftermarket wheels which I think you have...
Not quite sure I understand your explanation here as the distance traveled is directly proportional to the revs/mile X tire circumference. A different size tire will affect your trip computer calculations as the multiplier will be off with any size not matching stock tire circumference.
What I mean is the relationship between speedometer/odometer readings and your trip computer results will remain constant without regard to tire circumference, because all three are calculating distance based on axle revolutions, not the distance covered with each revolution.Not quite sure I understand your explanation here as the distance traveled is directly proportional to the revs/mile X tire circumference. A different size tire will affect your trip computer calculations as the multiplier will be off with any size not matching stock tire circumference.
What I mean is the relationship between speedometer/odometer readings and your trip computer results will remain constant without regard to tire circumference, because all three are calculating distance based on axle revolutions, not the distance covered with each revolution.
Keep in mind that the mpg computer must calculate fuel using engine load as well...
Maybe that's why I'm always getting better than the trip computer readout. I tend to fill up pretty close to the brim.The float in the tank can only travel up and down so much, so any fuel amount above and below that travel will go uncalculated...
Opps, I ‘meant’ TRIP in terms of MPG, not odometer. I meant to ask if/how do you adjust the OEM MPG computer for the large diameter wheel size.Different tire sizes won't affect the trip computer, per se, as the computer calculates distance based on the number of axle/wheel revolutions, not the actual distance traveled. The upshot is:
...Auto manufacturers program most cars (speedometers/odometers/trip computers) to read "optimistic" by 2-3%. This means if your speedo reads 50 mph you're probably doing an actual 48.5-49.0 mph - - to keep you on the safe side of the law, etc.Opps, just realize I tyupe
...When your odometer reads 50,000 miles, you've really only gone about 48,500-49,000 miles.
...Thus, your MPG calculations are generally optimistic by 2-3% because you really haven't driven quite as far as you thought.
I lucked out with my aftermarket wheels/tires (225/40-18) because my speedometer is close to dead on, as confirmed by carefully observing my speedo when driving by several different roadside radar displays. So, even though my tire size results in accurate speedometer readings, the trip computer's average MPG computations are still off. I agree, it would be nice to fine-tune the trip computer's average MPG computations, but I won't hold my breath for that. (yawn)
