NikonGuy

iTrader: (1)

Not sure if true for anyone else but so far I have had two fill-ups and in car mileage is a bit higher than actual calculated mileage (miles vs gallons at pump)

Most recent one in-car was 28.4 but actual was 26.2, a variance of around 8%. To me that is pretty high variance in numbers.

I have a 2008 IS250 with 75K BTW.

jonathanz

iTrader: (2)

my 2012 IS250 AWD computer show 20.4 but my math is 18.8

darkdream

There are numerous treads on this. All manufactures are higher than actual. Some vary as much as 20%.

JohnLX300

iTrader: (2)

I have an 2008 IS250 with 74k, same issue. Although I have to say I have been trying to keep track with an Excel spreadsheet. After about 10 fill ups. On average my actual gas mileage is about 3mpg less that what is stated in the car under my driving conditions/style.

Noeh

iTrader: (3)

Same here, about 2mpg lower every time.

VTsuckah

iTrader: (1)

My calculated mileage is actually about 0.2 mpg above what the computer calculates and displays.

Bichon

My hand calculated MPG is consistently higher than what is displayed on the trip computer too.

robtwo

The wider the gap generally means dirtier injectors.

Also consider each pump doesn't stop at the exact same spot. So this type of measure has a lot of errors in it. Pump, Pump stop point, miles, actual miles, user error etc.

jdmSW20

iTrader: (12)

usually my car is around the general ballpark of what im actually getting so i just leave it at that. its close enough. but like stated above there are so many variables into it, i just stick with the ballpark figure and keep it moving

FSportIS

iTrader: (13)

I don't think so. My brand new 2012 car would not have dirtier injectors than a 2006 car lol.

After several months of testing this, I can confirm this:
IS250 2012, On average: computer shows: 25, actual: 22.6 over the course of 3 years. It is 2.4 MPG higher than actual.

IS350 2006, on average: computer shows 19, actual: 19. It is spot on almost EVERY TIME over the course of several months. The margin of error is about 0.1-0.2. I'm very surprised.

I speculate that on IS250, computer displays 2+ MPG better than actual and on IS350, computer displays more accurately may be 0.1 or 0.2 higher. The ones who have almost accurate results are driving IS350???

Gerb

^ how do u decide which car to drive lol. You have a 250 and a 350. Why not drive 350 all the time?

jsh139

I haven't calculated the long-range MPG calculation, but in my car the "tank MPG" is very accurate by my calculations. It's usually spot on, or a few decimal places off.

FSportIS

iTrader: (13)

I drive them both. Fordaily commuting to work with bad traffic, IS250 to save gas. Weekends, autocross, track, IS350 for fun

IS250 is a lot more pristine, clean with more cosmetic mods so it is daily driver for show so I drive this to work

FSportIS

iTrader: (13)

I believe you drive the IS350 then. My IS350 is spot on and accurate while the IS250 almost always displays 2+ more MPG lol.

Why do Lexus do this, trying to fool people into believing that IS250 has way way better MPG than IS350?? In reality is, the difference is only 1-3 MPG difference.