Have you noticed a change in mpg as reported by the car?

 

I believe the computer uses the latest average mpg to calculate/project the next total range. It is meaningful if you drive the same way as before and the same road/car conditions etc. - it is an estimate.

 

I get better mpg when the weather was warmer and less than colder. Inconclusive data at the moment still.

 

No cars accurately show MPG for it is impossible for the metering system to properly measure such small amounts of fuel. I have found that my previous hybrid Priuses (Prii?) all were extremely overstating the MPG by more then 20%, and so much so that on PriusChat, they developed a simple algebraic formula to correct this. On the Lexus, it is off, but only a small amount, so just accept it. It is intentional by design to make you think you are getting better mileage and be happier with the car. The worst really is the BS on EV cars, where they base the MPGe on National Average Cost of ~$0.12 per kWh, while in sunny So Cal Edison land, this cost is more then 5x as high at ~$0.70. So a car that claims 100 MPGe really is getting 20 MPGe. Fortunately they have plans that bring it down to ~$0.30 but if you dare to turn on your home AC between 4 and 9pm, all your savings are lost. There is no winning, but it is the lies that are bothersome. The sticker should be based on averages WHERE THE CAR IS SOLD, both in cost of gas and electricity. But if they did that, the EV car sales would plummet. My $0.02.

 

Thanks for the reply.

I had forgotten about this thread - and learned to live with the discrepancy. I was talking to my dad and he found a mechanic online who answered the question the same way you did - it is certainly not measuring gas at the tank, it is calculated based on injector opening and closing times, duty cycle, fuel pressure, fuel return line, intake manifold pressure, ambient conditions, etc. So clearly this cannot be accurate with all these variables and minuscule volumes, and I've accepted that being off 5-8% is not too bad. I'm still getting really good mileage based on my own calculations (33 mpg averaged over a whole year, but about 36 mpg in the warmer months and suffering in the dead of winter).

 

I've tracked and calculated MPG for every fill since owning the car now almost 15 months and over 6,000 miles. Which means it's not even broken in yet. My dash shows the running average as 46.3 (just ticked the .3 this morning. Was .2 prior). My calc runs very close to the car's stated MPG. Now--I really hyper mile around town where I get the best MPG of course. But as stated--so many variables. The biggest being driver behavior.

 

good to know MPG improved over the course of 5 fill-ups :-)

 

My 16' RX 350 was incredibly accurate with my calculated values (+/- 0.25 mpg). My NXh is +/- 2.0 mpg