I only have one tank on my TCH and who knows how the dealer topped off the first tank. I calculated low 32MPG the guage said just over 33MPG. Currently I the reading for my second tank is 34.8 MPG, I will still go a few more days on this tank and will top it off the same way I did the fist fill up, so I should be able to see how off the guage is, but as many of you have several tanks are you trusting the guage or manually calculating it? My 04 and 04 Acura TLs were almost spot on for MPG reading, my Infinit I30 and I35 were off usually by 2 MPG. What is the feeling on the TCH?

I've only filled up 4 times so far, but I've found the indicated MPG to average about 1 mpg higher than I manually calculate. Click on my TCH MPG below and you will see my tank info. I've been adding comments to each tank so far.

I've done 4 tank fill-ups and so far the computer has been about 1 MPG higher than the manual calculation.

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As I just filled up today for the first time, others will fill you in more acurately than me, but my average was 33.9 and my actual was 34.8 - I was surprised by this as most, I think have the actual slightly lower...

Nash - what kind of driving conditions do you mostly drive in (Hwy, county hwy, cit) Your tank averages have to be from mostly highway! Great work!!

My manual calculations have been .1 MPG higher then the computers (second tank today not including the dealers fillup).

Pretty darn accurate.

Seven tanks; Car computer has always been slightly higher, by an average of 0.85 MPG.

I have just updated my excel sheet with my milage and tank info. I typically have been anywhere between 0.5 and as much as 2 miles per gallon off between the indicated tank average and my calculated average. To be consistant I mainly use the same station and try to give two squeezes after the pump kicks off. I have been above as well as below the indicated with the actual differences.

However, working backwards I have taken the "indicated" mpg and calculated the theoretical gallons used to get a number and then use the actual miles and I calculate the lifetime tank "indicated" with these numbers. Currently my lifetime tank indicated is 39.42 mpg over 7880 miles. My actual lifetime calculated actual is 38.63 mpg.

Now the problem is, with these numbers I am also assuming the odometer is correct but other posts as well as my observations from mile post on the interstate is that the odometer is also off by as much as 7%. If that was true then my indicated 7880 miles would actually be 7328 miles and thus my actual FE would be 35.93 mpg.

Also my 36,000 warranty would really be a 33,480 mile warranty.

What numbers do we use????? I'll stick with the odo reading and the actual gallons pumped. Right or wrong, they are the most arguable numbers to use. They are also comparable with other vehicles as most all spedo's have error.

Yes, I noticed the speedometer is off by a few MPH. When the speedo says I'm doing 60, I am really only doing 57 MPH. And I tested this 2 ways. Once by using mile markers and a watch and several times with those side of the road radar displays the police put out to slow you down. Of course that would throw off any MPG calculations based on the odometer.

You don't think Toyota has set the speedometers wrong on purpose to inflate the MPG numbers, do you?

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Tire pressure also plays a role.
Over inflated tires (like some of the folks here who are running 40 something lbs instead of the manufactures recommended 32 lbs) can mess with the speedometers calibration.

There are a lot of variables involved.