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Discussion Starter · #1 ·
On a recent trip to Houston from Cali, I finally realized something. Like most people I was upset about my mpg and almost rented another car to take. Once I got to Arizona, I started paying closer attention to my trip counter and noticed I was only getting 0.9 on the trip compared to the mile markers on the side of the road. I thought it was a fluke but I did it for 100 miles and then 1000, where my trip was showing approx 90 and 900 respectively. Basically, the trip looses .1 of a mile for every real mile i drive. It sounds small but see what happens.......
MILES GALLLONS MPG ADJ MPG
240.2 8.78 27.3 30.1
162.7 5.89 27.6 30.3
250.1 8.91 28.0 30.8
261 9.28 28.1 30.9
99.9 4.66 21.4 23.6???
209 7.51 27.0 30.6
74.1 3.23 22.9 25.2
210 8.04 26.1 28.7
214.3 8.00 26.6 29.4
180 6.98 25.7 28.3
217.2 7.29 29.8 32.7
122.2 3.93 31.0 34.2
291.2 9.67 30.0 33.3

2709 27.03 29.7
2979

Also,keep in mind that on this trip, the speed limit is between
70-80 mph and if i would have driven like a grandma like some of you suggest then I literally would have gotten run over. I am talking to the dealer to try and get this resolved but I am a lot happier getting close to 30-31 mpg than i was at 27-28. My suggestion to you is to see if your trip is working correctly and recompute your mpg and you might be happier too. Hope it helps.....

_________________________________________________________________
I have now entered my zen-like relationship with my Box
 

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With the stock OEM tires the odometer is about 3-4% short. One needs to do as you did, and calibrate the odometer with a reliable outside measurement.

This is especially true if one has changed to other-than-stock-size-or-brand tires. :)

For Vanilla, my odo was 3% off with the original tires, and 6.1% off with my aftermarket, different size, different brand tires. To get accurate MPG I used to multiply my indicated miles by 1.03 to get actual, now I multiply by 1.06.

For the correction you need, the multiplier is 1.1, of course. :)

Tom
 

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Discussion Starter · #3 ·
its cool... i just didnt know there was a difference between trip miles and actual miles, must be my ignorance. also, my box came with the 18s and speed hasnt changed at all. but i am definitely a lot more happy about the mpg now
 

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If you also go with a larger tire (ie larger wheels plus tires) the trip will be less than actual. And your going faster than it says you are.
 

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Discussion Starter · #5 ·
actually, no i am not. i did a 30 min actual count and checked the speed through some calculations and it worked out fine. only thing wrong is the trip counter. just wanted to have people check theirs out cause it could be under or over. scion admitted to having a problem with this. havent checked the trip vs odometer yet
 

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Trip and odo are identical.

As provided by Scion, at highway speeds, the odo is approximately 3% short of actual and the speedo is about 3% optimistic (this varies, depending on manufacturing tolerancees).

When I went to one size larger tire on 15" wheels (went to stock bB size: 185/65TR15), I increased the diameter by 0.7 inch. That corrected my speedometer to "right on" at 60-70MPH, but doubled the error in my odometers (to 94 indicated = 100 actual).

So long as I know the error exists, and how much to correct for, there is no problem.

(And no, there is NO wheel/tire combination that will give correct readings on both odo and speedo at the same time. Also, there appears to be no easy way to correct or re-calibrate the odo so that indicated and actual are the same.)

BTW, the repair manual for the xB actually SPECIFIES how much error the speedo is DESIGNED to have at different speeds.

Tomas
 

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al74dart said:
I will also be adding a fuel additive called Ethos FR, 1 ounce per 10 gallons of gas that has been proven to give you better gas mileage and cleaner exhaust emissions. I was so impressed with the reviews that I just signed up to buy it at a discount for myself. After I signed up I was talking to my friend about it and he told me he had used it and it did infact improve his mileage about 10%. Here is a link so you can take a look at it and deside for yourselves.
http://www.gasclubusa.net/go/daviddameron/ :)
This is some info on the same topic from a few weeks ago, a few other people have posted positive testament about the product. The link didn't work for me.

Incidentally, I noticed about a 5% error in my odometer. I'm getting better gas milage than I thought but you have to keep that in mind when planning your suggested maintenance schedule. Another bonus, when it's time to sell/trade-in you will show less than actual miles too!
 

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TheOtherGuys
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When I had my Scan Gauge installed in my ride my speedo was about 5mph faster than the ECU was telling the scan gauge. Example: Speedo said 55 scan gauge said 49mph. I'm running 18's w/ 215/35/18 tires.
 

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oldwhitedude said:
My '05 BCP xB has 26k miles on it. I put new Denso Irridium spark plugs in and my mileage went from 30.95 to 32.05. The plugs cost $10 each but were simple to change. My wife and I drive in often heavy traffic in the Puget Sound region of Washington state. We don't really pay attention to how hard or softly we drive.
The $40 dollars spent plugs, if spent on gas, would only get you about 13.5gallons or about 405 extra miles. In the long run, this makes good sense since plugs last a while; fuel additives might not save money in the long run since they do not last like plugs, etc.
 

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For those surprised that the speedo is not 'right on,' here is the calibration spec from the repair manual showing how far off the speedo is required to be to be in spec...

 

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^^^ Seems about right^^^
 

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I completely forgot I can test it on the dyno! DUH! When I put it back on, Ill let you guys know how off it is. I am running stock tires right now at 36psi of pressure. Dont forget to check your pressure guys. It sounds like a small thing but can make a significant difference.
 

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Padanky, im glad you said that re: your scan guage. I just recently installed an OBDII reader by Brockway Engineering (quite impressive, im posting pics in lil while) and my car speedo was 3 miph faster than the ecu was reading. I did get 17" wheels with 215/40/r17's, which i was sure would affect things but i didnt know how much.
 

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FYI ... im running a 215/45R17 set up ... and at every speed trap im running exactly what is showing on my speedo. MPG .. im getting roughly 32 to 33. Thats with the OEM Autolite plugs changed every 25K miles. Gapped to .44 where as the OEM JDM plugs ( NKG i believe ) are gapped to .32 You can get the Autolite plugs at Wally World, 2 for $2.96.
 

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Discussion Starter · #16 ·
i appreciate all the ''help'' and all i was trying to do is share this info with people who didnt know. my stock vs my 18s is VERY insignificant as far as a difference there cause i actually measured them out. i am now getting 33-36 mpg depending on where and how i am driving. this is just a reply to the post in another thread wondering if the problem with mpg was user or manufacturer......the answer is both.
 

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Played with my trip on a 200 mile trip this weekend and found that it was off about 7.8-8.0%.
 
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