MPG Calculations Are Just Plain Wrong
#1
MPG Calculations Are Just Plain Wrong
In an earlier thread, I was trying to understand why the miles-per-gallon calculated by the car was higher than the actual (i.e., how many miles I drove between fill-ups divided by the actual gas I put in)
I can understand the calculation being off a bit in any single tank, particularly if there wasn't a complete fill one time and the car took more gas another.
BUT...
As I compare the computer readout with my actuals over several consecutive tanks, I'm ALWAYS coming up with a difference.
Simply put...
The car is regularly reporting MPG approximately 2 higher than what I compute.
Last tank was almost pure highway. Drove 383.5 miles. Car said my MPG was 30.1 as of the time I pulled into the gas station. I expected to take something like 12.7 gallons. Instead, I took more like 13.6 - MPG turned out to be 28.2
If this was a one time fluke I'd shrug it off - but now I'm thinking there's just something unreliable in how it calculates MPG.
Have others had a similar experience with the car over-reporting its MPG?
I can understand the calculation being off a bit in any single tank, particularly if there wasn't a complete fill one time and the car took more gas another.
BUT...
As I compare the computer readout with my actuals over several consecutive tanks, I'm ALWAYS coming up with a difference.
Simply put...
The car is regularly reporting MPG approximately 2 higher than what I compute.
Last tank was almost pure highway. Drove 383.5 miles. Car said my MPG was 30.1 as of the time I pulled into the gas station. I expected to take something like 12.7 gallons. Instead, I took more like 13.6 - MPG turned out to be 28.2
If this was a one time fluke I'd shrug it off - but now I'm thinking there's just something unreliable in how it calculates MPG.
Have others had a similar experience with the car over-reporting its MPG?
#3
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Originally Posted by CGTSX2004
The car is always going to be a little more optimistic. I track my mileage and have noticed the same thing. Essentially, it boils down to the fuel sensor in the car being more optimistic than it should be.
#4
everyone knows that the computer readout is always wrong(regardless of car)...the only real way is to do it the old fashion way and fill up your car(reset mile counter) drive around for awhile, then top it back off at the sae gas station and pump..
divide the miles driven by gallons used.
divide the miles driven by gallons used.
#5
2006 DGP Sold 10/24/2012
Originally Posted by amg212
The car is regularly reporting MPG approximately 2 higher than what I compute.
Have others had a similar experience with the car over-reporting its MPG?
Have others had a similar experience with the car over-reporting its MPG?
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#8
do you realize that complaining about 29mpg instead of 31mpg is like splitting hairs? who cares? 2 less mpg over a tank = ~30 miles less. i'd say that you guys shouldn't worry about $2 every time you fill up, but then again, i see more and more posts about how you're 18 and daddy bought your TSX, how it won't go 167mph, etc etc.
ugh.
ugh.
#9
Originally Posted by frescagod
do you realize that complaining about 29mpg instead of 31mpg is like splitting hairs? who cares? 2 less mpg over a tank = ~30 miles less. i'd say that you guys shouldn't worry about $2 every time you fill up, but then again, i see more and more posts about how you're 18 and daddy bought your TSX, how it won't go 167mph, etc etc.
ugh.
ugh.
BTW, I haven't seen any posts lately regarding a 167mph tsx o.O?
#10
Drifting
Originally Posted by sccpu3d
Well, im not really complaining or anything, but i could see 30 miles less is about 1 gallon, and if you fuel up every 3-4 days, thats a difference of 104 gallons to every year. Then again, its only about 300 bucks difference every year, which is basically 1% of the car
BTW, I haven't seen any posts lately regarding a 167mph tsx o.O?
BTW, I haven't seen any posts lately regarding a 167mph tsx o.O?
#11
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Originally Posted by amg212
As I compare the computer readout with my actuals over several consecutive tanks, I'm ALWAYS coming up with a difference.
Simply put...
The car is regularly reporting MPG approximately 2 higher than what I compute.
My only other complaints involve the GPS navigation, but I guess that is another thread.
The car itself is great!
#12
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My MID says an average MPG of 18-19MPG, and when I do it the old fashioned way I caculate 18-19MPG. Now.....don't get me wrong, I am not happy with this....should be getting at least 20-23. I do mostly highway mileage. Anyone else find these low MPG with 3G TL's?
PS: Love the car in every other possible way
Edited: Sorry just realized this was a TSX forumn
PS: Love the car in every other possible way
Edited: Sorry just realized this was a TSX forumn
#13
Originally Posted by amg212
I expected to take something like 12.7 gallons. Instead, I took more like 13.6 - MPG turned out to be 28.2
#15
Originally Posted by sauceman
Gas stations are regularly inspected by weights and measures agency, .
#16
Originally Posted by BBriBro
How do you know the gas pump is accurate? That is just one more variable to consider. Maybe you only pumped in 12.7, but they charged you for 13.6, if it errs in their favor, I doubt they'll be in any hurry to recalibrate it.
I have no idea what the standards are for those things, just throwing out another thing to consider. .
I have no idea what the standards are for those things, just throwing out another thing to consider. .
edit - i see the moderator already replied to your post.
#17
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Originally Posted by BBriBro
I'm sure that's true, but how would you know if it was off ? We've all seen it where if you put a full 5 gallons in a 5 gallon can it will be flush with the threads in the cap, I can't imagine that the "full" mark would be right at overflowing, with no air space, just too many variables in my opinion.
#18
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I worked at a gas station for almost two years in college. We were inspected by weights & measures four times during that period and never needed to recalibrate anything. And these were with some fairly old and crappy pumps. Unless you are filling up at a REALLY old station I doubt there will ever be any measurable drift between W&M checkups.
What I *would* expect variation in is the amount of gas you can fit into the tank on any particular day. Between thermal variations in the density of gasoline and some random factor in when exactly the pump stops I wouldn't be surprised to see a variance of half a gallon or more.
What I *would* expect variation in is the amount of gas you can fit into the tank on any particular day. Between thermal variations in the density of gasoline and some random factor in when exactly the pump stops I wouldn't be surprised to see a variance of half a gallon or more.
#19
Maybe the takeaway is simply this...
The MPG calculation on the car will always lack precision - and if you're looking for precision, you're out of luck.
However, if you want a good guideline, it is useful.
(e.g., 29 vs 31 is splitting hairs, but 29 vs 23 makes a difference)
The MPG calculation on the car will always lack precision - and if you're looking for precision, you're out of luck.
However, if you want a good guideline, it is useful.
(e.g., 29 vs 31 is splitting hairs, but 29 vs 23 makes a difference)
#21
Originally Posted by jpt
What I *would* expect variation in is the amount of gas you can fit into the tank on any particular day. Between thermal variations in the density of gasoline
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