The computer uses the signal from the #1 injector to calculate fuel mileage. It's not a weighted average, but there is an assumption about fuel density.

Which brings up another possibility. I got my best fuel economy ever in my IS on my trip to New Mexico after a fill up near Tucson. With the cruise set at 80 mph, I got 30.5 mpg, just like in the picture. The best I have ever seen on California fuel after absolutely babying the drive for maximum economy was 29.0 mpg. Lately it's been hard to break 26 mpg even on a long freeway speed trip.

I suspect there is less ethanol in Arizona gas, and less oxygenates in general which means their fuel has more specific heat and will always give better mileage than the evil watered down **** they sell us in California for absurdly jacked up prices (yes, gas was $0.55 a gallon cheaper in AZ too!) CARB screws us with fuel that costs more to make & buy, gets worse mileage, and salts the wound with smog inspections after four years.

Get branded a high emitter because your car is a Supra and you get Test Only on your renewal despite only getting 12 mpg from the gas they sell that used to give 18 mpg in the same car. But I digress.

I completely believe it is possible to get the mileage KMRIS350 is claiming in Arizona, even zooming around a little. I don't doubt it a bit.

 

Has anyone ever validated the estimated tank MPG? I would love to believe it's accurate as I get 22.5-23.5 in town displayed on the LCD panel with my 350

 

i got 28mpg once that showed on the dash. my average driving local was about 320 per tank; average freeway 400 to 415 per tank. The highest I've gotten was 427!!! I was very surprised how a 3.5L can do so well.

 

the tank avg resets everytime you fill it up...also when i fill up my car I dont fill it up all the way I usually put in around 20$. Does that have anything to do with my mpg. btw my tank avg is 13.7 hahah i dont get it

 

100% city driving I get 19.5-20.0 mpg

 

I have nothing to add about your low mileage but can only give you what I've been getting on my IS250. I routinely get 25 mpg when driving mostly in the city but on the highway......well here's a good example. Driving down to San Diego and back, a distance of about 180 miles, and driving in the range of 65/85 depending on traffic the computer returned 33.2 mpg for the entire trip. Just what I was hoping for when I opted for the 250 over the 350. This is even a little better than my C-230 Mercedes returned which was in the area of 30/31 mpg driving the same speeds and route....

 

Do you do lots of short trips? I've found that nothing kills gas mileage on this car more than short trips in cold weather.

 

i normally top out at 320 miles with 60% city and 40% highway on my 350. which i believe avgs out to 19-20 mpg. but i havent had my first oil change yet so maybe after the 1st change itd get better.

 

Your fuel economy should gradually improve as the engine breaks in, but there is no magic about the first oil change that would cause a sudden jump in mileage after that service.

 

Wow... Apparently however I have been driving is EXTREMLY bad for my MPG . I have a 250 w/ 2,850 miles on it and I have NEVER Gotten over 22 MPG... I drive to school everyday which is like 2 miles away and to friends houses and such... Apparently short trips is the worst thing you can do to your car ;(. I figured I would at least be getting 24 on average. But normally I get about 18 - 19 MPG on every fill-up ;( I cant imagine what I would be getting w/ the 350!!