Inaccurate mileage report?
05-22-13, 01:43 PM
#1
Intermediate
Thread Starter
Inaccurate mileage report?
Has anyone else checked the MPG Since Last Fillup numbers against computing the actual miles driven and fuel used manually? I find the (2011 460) numbers to be consistently 2 mpg or more higher than actuality. To be as accurate as I could I used the same pump at each filling, letting it stop automatically when full. I now wonder at the accuracy of the "total mpg"--which shows 14.1 for 15,000 miles. I drove 5000 of those, and never got more than 12.5 mpg (by the Lexus meter.)
05-22-13, 02:43 PM
#2
All 4 of my Lexus cars and my previous Toyota Prius and Avalon display MPG consistently exaggerated 5%.
I log every fill-up and compare MPG calculated via pencil to what the car displays.
JR
I log every fill-up and compare MPG calculated via pencil to what the car displays.
JR
05-22-13, 02:47 PM
#3
Has anyone else checked the MPG Since Last Fillup numbers against computing the actual miles driven and fuel used manually? I find the (2011 460) numbers to be consistently 2 mpg or more higher than actuality. To be as accurate as I could I used the same pump at each filling, letting it stop automatically when full. I now wonder at the accuracy of the "total mpg"--which shows 14.1 for 15,000 miles. I drove 5000 of those, and never got more than 12.5 mpg (by the Lexus meter.)
http://www.fuelly.com/driver/flyct/ls460
JR
05-22-13, 04:25 PM
#4
Gas Mileage
I have owned three Lexus vehicles and a dozen Toyota's over the years. Mine all have been pretty much right on. The miles left until empty is based on when the gas tank low light comes on, not when the tank is completely. Presently drive a 2012 LS460 AWD and a Toyota 4Runner. I check them occassionally and the numbers jive. They sometimes vary by a few tenth's.
05-22-13, 04:59 PM
#5
"letting it stop automatically when full'
it is almost impossible to fill the tank to the exact same level from fill-up to fill-up. This probably accounts for the discrepancies. It is virtually impossible to get an accurate mileage figure unless you fill the tank to the exact same spot each time. Letting the gas nozzle stop the fill automatically does not insure that the fill level is exactly the same each time.
I have a Scan Gauge and I've used it on two of my other Lexus vehicles, and the onboard computer was actually always quite accurate compared to the Scan Gauge.
it is almost impossible to fill the tank to the exact same level from fill-up to fill-up. This probably accounts for the discrepancies. It is virtually impossible to get an accurate mileage figure unless you fill the tank to the exact same spot each time. Letting the gas nozzle stop the fill automatically does not insure that the fill level is exactly the same each time.
I have a Scan Gauge and I've used it on two of my other Lexus vehicles, and the onboard computer was actually always quite accurate compared to the Scan Gauge.
05-22-13, 05:03 PM
#6
Here's a link to my 5000 or so miles tracked on my 2009 LS460.
http://www.fuelly.com/driver/flyct/ls460
JR
http://www.fuelly.com/driver/flyct/ls460
JR
05-22-13, 07:24 PM
#7
We track all our cars. http://www.fuelly.com/driver/flyct/
JR
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06-03-13, 06:28 PM
#9
Intermediate
Thread Starter
How accurate is mpg reading.
[SIZE="2"]Sorry for the delay. I'll try to respond to all now. Lavrishevo-Congrats on 29.1 mpg. The question is the accuracy of the reading. EllliotB-Your points would be well taken if there were but a few samples. I have filled it up as described dozens of times, consistently about 15% off, if I did the math right. If the instrument said 14 mpg, for example, the actual would be about 12 mpg. Vally101--with respect, going by the "low" light cannot be as accurate as actual miles driven and gas used. FLYCT--5% off isn't bad.
To all--Thanks for responding. I didn't mean it to be a contest, just an exchange of info.
To all--Thanks for responding. I didn't mean it to be a contest, just an exchange of info.
06-03-13, 08:11 PM
#10
Got you beat. This is after traveling 200+ miles at 75 MPH with my 2009 LS460 with the Air Conditioning on. At 60 MPH it's even better.
Jr
06-03-13, 09:06 PM
#11
Intermediate
Thread Starter
It sure reads good. But we still don't know if it's accurate. Where were you able to do 75mph for 200 miles? I think Lexus wouldn't claim 30 mpg at that speed.
06-03-13, 10:11 PM
#12
Yes, I did 210 miles with cruise set to 74 MPH (speed limit 70 MPH). There was 10 miles where I had to slow to 65 MPH due to reduced speed limit of 60 MPH for construction, and it included one stop for bathroom break. I do this trip often. I-75 from Ft Lauderdale to Bradenton Fl. It's very flat terrain at sea level to 65 ft MSL max. No hills other than overpasses.
After the 210 mile trip I drove an additional 125 miles of city driving before filling up. Fillup took 13.51 gallons for the 335 total miles. The car displayed average since last fillup of 26.0 mpg but when calculated via pencil it worked out to 24.8 mpg. Typical 5% display error. Calculated 62% highway, 38% city driving.
Tailwind vector on the 210 mile trip was 10 MPH. Without the tailwind the displayed average mpg usually reads between 28.5-29.5mpg at the cruise speed.
With my CT200h the wind factor is more significant.
JR
After the 210 mile trip I drove an additional 125 miles of city driving before filling up. Fillup took 13.51 gallons for the 335 total miles. The car displayed average since last fillup of 26.0 mpg but when calculated via pencil it worked out to 24.8 mpg. Typical 5% display error. Calculated 62% highway, 38% city driving.
Tailwind vector on the 210 mile trip was 10 MPH. Without the tailwind the displayed average mpg usually reads between 28.5-29.5mpg at the cruise speed.
With my CT200h the wind factor is more significant.
JR
Last edited by FLYCT; 06-04-13 at 06:23 AM.
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