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If you havent had your speedo recalibrated youll wanna do that. If you know anybody with a smarty that would be the easiest the only other way i know is through a dealer maybe somebody else has some ideas. To figure mileage you will want to fill up and reset your trip. Then the next time you fill up take the number of km your trip is showing and divide by the amt of fuel you just put in your tank. You can do it now and get a decent idea but wont be accurate until you get recalibrated.

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The ecm needs to be programmed for the larger tires to be accuarate. If it came stock with 245's or even 265's those 35's will show less milage than you are actually going. I am sure someone here can give a precise number that the odo would be off. you are going further every revolution on the 35's vs stock since the diameter is greater. i am not sure how much differance but ther will be some.

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Ive been using the odometer... it would be out you figure? - - - Updated - - - best I got was 600km or 650km I cant remember that was bone stock. now I filled up last night and I got 92 km and its still over full! is this good???? . I never once got into the throttle, kept my smoke down to none at all basically, and drove a steady 55mph. about 8 km of that is not highway. If i go fill up right now how would I calculate my miledge? i have my receipt from last night: (this was almost on the fuel light) litres: 95.38 price: $1.17/L total: $112.45 so how many litres would my tank hold? im confuseed on how to figure out my miledge. im gunna go top up my tank and see what I get! - - - Updated - - - this is my truck p.s

My tank holds 134.5 L but my truck is reg cab long box so yours might be different.
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I just got back from Ontario, OR and Nampa, ID for a 240 mile round trip and still got 19.8 MPG using my heavy winter 265/75 R16's... But I'm so spoiled to having much high numbers.

:think: Ive not been having any luck with my scangauge. Ive gone over the instructions several times hopiing i missed something but ive done everything to the t. The only time it shows believable numbers is when i have to be in the throttle to maintain a speed or when im acceslerating. But when im on flat ground and maintaining a speed it gets way outta whack. Its constantly off by 4 to 6mpg and its off by several gallons every fill up. Anybody have any luck with one of these with an automatic? I just dont know what i could be doing wrong...
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:think:

Ive not been having any luck with my scangauge. Ive gone over the instructions several times hopiing i missed something but ive done everything to the t. The only time it shows believable numbers is when i have to be in the throttle to maintain a speed or when im acceslerating. But when im on flat ground and maintaining a speed it gets way outta whack. Its constantly off by 4 to 6mpg and its off by several gallons every fill up. Anybody have any luck with one of these with an automatic? I just dont know what i could be doing wrong...

1. Pick one station and one pump. Make sure you use the same station, pump and parked the same direction.

2. Fill up till the handle cancels on its own. Use the slowest notch for best accuracy. Do NOT top off!

3. 1st fill up don't change the display just go through the process but remember no adjustments!

4. Return back to the station after a 1/2 to 3/4 tank is burned. Same station, same pump, Same direction!

5. Fill the tank again same way. Slowest notch and let it cancel. Do NOT top off!

6. Now adjust for offset.

7. Your done.

Like me when I do calibrations to my ScanGauge II I use Payette, ID Maverik station and pump #1. I pull it the same way each time and it I can hit the number dead on the nail each time. As soon as the handle cancels it right there. At the worse I've seen +/- 0.1 or 0.2... If still that close I leave it alone. Density change of fuel and temperature.

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The ecm needs to be programmed for the larger tires to be accuarate. If it came stock with 245's or even 265's those 35's will show less milage than you are actually going. I am sure someone here can give a precise number that the odo would be off. you are going further every revolution on the 35's vs stock since the diameter is greater. i am not sure how much differance but ther will be some.

i found my speedo variance with oversized tires to not be a linear calibration. what i found is that at sub 50mph it seems to be very accurate with the gps. 60>mph it seems to skew further the faster you go... thats my experience anyway..
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okay.. so I got 103km on my od. i filled up, took 14.98L If i read and did the math right thats pretty much 19 MPG on that 103km not?I just wanted to see if babying the truck helped! i got 1/4th my usual mileage (400km-450km) for $17.42 and my fuel gauge still over full! I never realized driving like a grandma and feathering the throttle andkeeping the boost and smoke down would make that big of differance!so If my od is out because of my tires would this make my miledge go up or down?my buddy has a new hyper tech programmer for sale for $100.00. it wont work on his cummins cause somebody cut the data link off on his truck! :doh:should I buy this and get my speedo set up right? also can that programmer help my truck out miledge wise?

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okay.. so I got 103km on my od. i filled up, took 14.98L If i read and did the math right thats pretty much 19 MPG on that 103km not? I just wanted to see if babying the truck helped! i got 1/4th my usual mileage (400km-450km) for $17.42 and my fuel gauge still over full! I never realized driving like a grandma and feathering the throttle andkeeping the boost and smoke down would make that big of differance! so If my od is out because of my tires would this make my miledge go up or down? my buddy has a new hyper tech programmer for sale for $100.00. it wont work on his cummins cause somebody cut the data link off on his truck! :doh: should I buy this and get my speedo set up right? also can that programmer help my truck out miledge wise?

If I remember reading correctly you also cleaned your IAT sensor. I read this whole post because I have been having ther same problem with my 98.5 . She is getting around 13, I am going to clean that sensor later and see if it helps. If anyone has any other ideas about how to bring my mileage back up I'm all ears :shrug:. I also have bigger tires,315's to be exact, she also has: Edge Juice Box, new +100hp injectors,BHAF,Stock turbo, and an Air Dog 150. She runs around 18psi for fuel pressure but it bounces around a lot. I just got a new TPS that I am going to put on today too. I can get a little smoke out of her but only if I stand on it from a dead stop.
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1. Pick one station and one pump. Make sure you use the same station, pump and parked the same direction.

2. Fill up till the handle cancels on its own. Use the slowest notch for best accuracy. Do NOT top off!

3. 1st fill up don't change the display just go through the process but remember no adjustments!

4. Return back to the station after a 1/2 to 3/4 tank is burned. Same station, same pump, Same direction!

5. Fill the tank again same way. Slowest notch and let it cancel. Do NOT top off!

6. Now adjust for offset.

7. Your done.

Like me when I do calibrations to my ScanGauge II I use Payette, ID Maverik station and pump #1. I pull it the same way each time and it I can hit the number dead on the nail each time. As soon as the handle cancels it right there. At the worse I've seen +/- 0.1 or 0.2... If still that close I leave it alone. Density change of fuel and temperature.

I thought it was better to top off? I always fill up to the neck with just enough room for 2 stroke oil or just about 3 inches down into the neck and fill up with 2 stroke when I get home.

okay.. so I got 103km on my od.

i filled up, took 14.98L If i read and did the math right thats pretty much 19 MPG on that 103km not?

I just wanted to see if babying the truck helped! i got 1/4th my usual mileage (400km-450km) for $17.42 and my fuel gauge still over full! I never realized driving like a grandma and feathering the throttle andkeeping the boost and smoke down would make that big of differance!

so If my od is out because of my tires would this make my miledge go up or down?

my buddy has a new hyper tech programmer for sale for $100.00. it wont work on his cummins cause somebody cut the data link off on his truck! :doh:

should I buy this and get my speedo set up right? also can that programmer help my truck out miledge wise?

I would get it and try it out, you could always get your money back out of it if you dont like it.

If I remember reading correctly you also cleaned your IAT sensor. I read this whole post because I have been having ther same problem with my 98.5 . She is getting around 13, I am going to clean that sensor later and see if it helps. If anyone has any other ideas about how to bring my mileage back up I'm all ears :shrug:. I also have bigger tires,315's to be exact, she also has: Edge Juice Box, new +100hp injectors,BHAF,Stock turbo, and an Air Dog 150. She runs around 18psi for fuel pressure but it bounces around a lot. I just got a new TPS that I am going to put on today too. I can get a little smoke out of her but only if I stand on it from a dead stop.

We have almost the same truck but im running 305/70/17 and bigger injectors. When mine was an automatic the best I could get was about 16 mixed hwy and city but with this 5 speed I get a hair over 18 driving the same way. I dont drive like an maniac but i dont drive like Mike either. Check my fuelly link out in my sig below, it says 16 because it was always low with the automatic but check the graphs out on the link to see how it changed.
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I thought it was better to top off? I always fill up to the neck with just enough room for 2 stroke oil or just about 3 inches down into the neck and fill up with 2 stroke when I get home.

The purpose is this:

same pump, same direction, same everything. filling it until it kicks off on it's own gives you the most accurate 'constant' for calculating MPG. If you tend to fill it beyond that point, then that 'constant' now becomes a 'variable'. You can easily add another gallon by 'topping it off', which will skew the mileage accuracy.

I always put my 2 stroke oil in just before I refuel, anyway; this allows the incoming fuel to mix with the 2 stroke well.

Another issue with completely filling your tank is that you leave no room for expansion/contraction of the tank and its contents. I've experienced completely filling the tank during the day, just before getting home, and getting up after a cold morning to find a little fuel had pushed out onto the ground due to the tank contracting.

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If I remember reading correctly you also cleaned your IAT sensor. I read this whole post because I have been having ther same problem with my 98.5 . She is getting around 13, I am going to clean that sensor later and see if it helps. If anyone has any other ideas about how to bring my mileage back up I'm all ears :shrug:. I also have bigger tires,315's to be exact, she also has: Edge Juice Box, new +100hp injectors,BHAF,Stock turbo, and an Air Dog 150. She runs around 18psi for fuel pressure but it bounces around a lot. I just got a new TPS that I am going to put on today too. I can get a little smoke out of her but only if I stand on it from a dead stop.

Come to think of it, my fuel pressure jumps around like 2-3 psi. But if I stand on my truck I can roal coal like crazy! Or as my buddy would say "youtube worthy" :P. I was a few minutes behind schedule this morning and I drove 75 mph the whole way to work and that 14 liter top off and then some is gone in 39 km's.
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:think: Ive not been having any luck with my scangauge. Ive gone over the instructions several times hopiing i missed something but ive done everything to the t. The only time it shows believable numbers is when i have to be in the throttle to maintain a speed or when im acceslerating. But when im on flat ground and maintaining a speed it gets way outta whack. Its constantly off by 4 to 6mpg and its off by several gallons every fill up. Anybody have any luck with one of these with an automatic? I just dont know what i could be doing wrong...

I have an auto as well and have exactly the same problems you have. Even with 'filling at the same pump etc'.
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i found my speedo variance with oversized tires to not be a linear calibration. what i found is that at sub 50mph it seems to be very accurate with the gps. 60>mph it seems to skew further the faster you go... thats my experience anyway..[/quote

I thought differences in speedo readings was a "percent" of actual. so, If you are off 5%, running at 50mph with larger tires you actually are going 52.5.... 2.5 faster than 'indicated'

at 60mph you are actually running 63 or 3 faster than indicated.

So, yes, that does make it worse the faster you go, and is still entirely 'linear'

Now, I haven't a clue to what it's doing when compared to 'GPS'.... (are the 'refresh' rates in those contraptions keeping up with ACTUAL conditions?):shrug:

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The most I can give is running out to a tire calculator and getting the figures... http://www.miata.net/garage/tirecalc.html But the problem is not all tires are the same. These calculations are rough estimates. Like my 265/75 R16's are suppose to 31.6 Inches but there not there closer to 32" inches when new. So even looking at the 235/85 R16's it suppose to 31.7 inches. Just the 0.1 of inch is equal to 1 rev per mile difference or 0.2% percent offset. But my truck already has a 0.5 MPH offset with the stock size and the ScanGauge II requires 1% offset to be even close to the GPS. So this shows even I'm not excluded from the offset problems. Even though mine or very very minor it does impact the hand math up to +/- 0.5 MPG offset. Here is a older video I did showing some offset.

http-~~-//www.youtube.com/watch?v=pq0XG5qRLsM

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true.

If I stay all city driving for the entire tank, the odometer and GPS are very close, usually within a mile or two..

If I add some highway driving in, or a lot of it, the difference I've seen can be as high as 35-40 miles more on the GPS than the odometer.

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I thought it was better to top off? I always fill up to the neck with just enough room for 2 stroke oil or just about 3 inches down into the neck and fill up with 2 stroke when I get home. I would get it and try it out, you could always get your money back out of it if you dont like it. We have almost the same truck but im running 305/70/17 and bigger injectors. When mine was an automatic the best I could get was about 16 mixed hwy and city but with this 5 speed I get a hair over 18 driving the same way. I dont drive like an maniac but i dont drive like Mike either. Check my fuelly link out in my sig below, it says 16 because it was always low with the automatic but check the graphs out on the link to see how it changed.

Mine has the auto tranny, so it sounds like I'm not gonna get much better mileage than where I am now, bummer :( I don't know if its the tps, which was tested by the dealer and was bad, but the truck surges alot at low throttle. Hopefully a new TPS and cleaning the IAT will bring it back around. Getting a little frustrating :ahhh:.
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