jooksing82

Any notice that the mpg reported from the car is higher than it actually is?
I track the mpg with an phone app every time I fill up. and notice a that the car reports a higher number every time. i.e. the phone app gives me 24 mpg while the 400h tells me 26.5 mpg.

The phone app is just a simple calculator/ data recorder of (miles driven)/(gallons of gas added) .

I will post my actual comparisons later when i get a few more comparisons. I know its an estimate but I feel there is a problem if the system is consistently reporting higher values.

chrispham

I would be interested to see that. I just purchased my RX400h about two weeks ago and absolutely love it. So far, I am seeing an average of around 26.5mpg but I live in an area that has a LOT of hills. I think if I were to live in an area like Texas the mpg would skyrocket but I could be wrong.

jakenbake

26.5?! The highest I have gotten in everyday driving is 22. But then again, I drive hard.

jooksing82

These are my last few gas fill ups from the phone app. 24.3, 24.5, 23.6,24.8,23.4,22.8,25.7, 25.3,24.3 9 summer time

here are my past winter numbers in Chiberia 17.9,17.7, 19.4, 19.5, 21.1, 21.6

I drive in heavy traffic (get best mileage...) ride my brakes fro 25 miles.... =(

I get about 22 when I drive highway speeds more.

is your 22mpg from the screen or actual gas fill ups?

chrispham

My 26.5 is is per tank. I notices the mpg's are going up pretty good on highway miles. I don't really drive in heavy stop and go city traffic. I've just had the car for around two weeks but I may start jotting down mpg's every time I fill up just to see what they look like. My mpg's are from the screen. But the second time I had to fill up, I double checked manually and the screen was correct on the mpg.

jakenbake

I have only ever gone by the screen. But I did reset my my mileage last time I filled up so I will do the math when i get gas in a couple days.

I'm curious about oil. I read somewhere that someones mileage jumped up 2mpg when they switched from regular to synthetic. Wondering if anyone uses synthetic and had the same results.

thomas1

Mine here in California is close, maybe off about 1 mpg. And our gas sucks. I average about 24.5.

alex1372

My fuelly - http://www.fuelly.com/car/lexus/rx40...lex1372/313496

takeshi74

Yup -- there are prior threads on this. Not just with the 400h but other models as well. Variance has been from 0.19 MPG to 3.26 MPG for me.

Neither method of calculating is going to be 100% accurate. The problem lies in expecting them to be the same given the differences in how the values are calculated.

jakenbake

Just went and filled up my gas tank. The instrument cluster said 21.6mpg and when I did the math it got 21.8mpg...Pretty dang accurate.

chrispham

I was told by the previous owner and also the Lexus dealership that the 400h I just bought takes synthetic oil. I just assumed it was mandatory like my Porsche. I'm guessing some people are using regular oil like the poster above? I am going to stick with synthetic. It's a ton more but worth it I think.

As far as mpg's. I am still averaging abot 26.6 per tank. I think I am on my 4th tank now. Can't seem to get it over 27, even trying to drive like a Prius owner ;-)

maseace

My info screen reported an average of 1.2 mpg higher than actual calculations from the pump receipts, over the past 2 years. It varied from 4.1 mpg higher to 3.5 mpg lower.

Weighit

I think some of that may be how full you fill the tank. I can have the pump quit, and if I rock the car, shake it a bit and then continue I can add 1.2 gallons of gas after the initial click off. Had I pulled the nozzle and divided miles driven to gallons added my mileage would be different than filling the tank right up. For my last 10 fill ups I'm at 21.8 mpg with the a/c running 100% of the time here in the Arizona heat. As winter approaches and the a/c can be shut off, that mileage will improve.

jooksing82

I like this layout.. I think i will need to switch the fuel logging app.

I got similar results, I understand the reasons of inaccuracies. My problem with it is that the error should not always be one sided...

For the record I am using Syn oil. Mobil 1!!! I do drive like a Prius Owner.. actually most Prius I seen fly past me! the Missy hates my "slow" driving.

I can understand how the way I fuel can affect the number on the current fill up, So I am consistent in the way I fuel up. I never top it off now, and I use the same gas station. The way you fill up should not affect your mileage by much when you average it over several thousand miles.... the little inconsistencies should get averaged out.

Here are my results over the last few months (winter months)

Actual mileage/Reported milage/Difference/% Error
18.3 mpg 19.7 mpg 1.4 mpg 7.00%
18.8 mpg 20.9 mpg 2.1 mpg 9.92%
18.7 mpg 20.4 mpg 1.7 mpg 8.26%
22.8 mpg 24.5 mpg 1.7 mpg 7.02%
18.3 mpg 20.2 mpg 1.9 mpg 9.59%
22.3 mpg 25.1 mpg 2.8 mpg 11.23%
21.9 mpg 23.8 mpg 1.9 mpg 7.92%
23.2 mpg 24.7 mpg 1.5 mpg 5.93%
22.2 mpg 23.6 mpg 1.4 mpg 5.85%
21.7 mpg 24.1 mpg 2.4 mpg 10.11%
25.8 mpg 27.6 mpg 1.8 mpg 6.44%
25.2 mpg 28.2 mpg 3.0 mpg 10.51%

AVG Mileage/AVG Reported/ AVG Difference/AVG Error
21.6 mpg 23.6 mpg 2.0 mpg 8.3%

The results are from ~3500 miles.