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New tires, lost mileage, what should I do?

Old Mar 19, 2006 | 06:53 PM
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New tires, lost mileage, what should I do?

I just added 33" Toyo M/T's to my truck with 18 moto metal wheels and my truck looks awesome! I'll post pictures as soon as the weather clears up.

Unfortunately my gas mileage has gone way down. I knew that adding the bigger tires and the M/T's my mileage would go down a bit, so I am not surprised. Question for all of you is what can I do to increase my gas mileage? Would a new exhaust help? If so which one? What about the Edge tuner?? Intake? Any suggestions would be greatly appreciated!
 
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Old Mar 19, 2006 | 06:54 PM
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Magnaflow exhaust,X2 or Edge tuner, Volant intake should help you ALOT!
 
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Old Mar 19, 2006 | 06:59 PM
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Thanks for the advice! I will submit your list of items to the boss (my wife) Wish me luck. It was hard enough getting her ok on the wheels and tires, but if I can explain that this stuff will help my gas mileage I may get her buy off yet!
 
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Old Mar 19, 2006 | 07:01 PM
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From: Plano, TEXAS
Originally Posted by mjandjason
I just added 33" Toyo M/T's to my truck with 18 moto metal wheels and my truck looks awesome! I'll post pictures as soon as the weather clears up.

Unfortunately my gas mileage has gone way down. I knew that adding the bigger tires and the M/T's my mileage would go down a bit, so I am not surprised. Question for all of you is what can I do to increase my gas mileage? Would a new exhaust help? If so which one? What about the Edge tuner?? Intake? Any suggestions would be greatly appreciated!
Intake, and exhaust.. If you want more after that some new gears will help out..
 
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Old Mar 19, 2006 | 07:02 PM
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Originally Posted by mjandjason
Thanks for the advice! I will submit your list of items to the boss (my wife) Wish me luck. It was hard enough getting her ok on the wheels and tires, but if I can explain that this stuff will help my gas mileage I may get her buy off yet!

Good luck man!
 
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Old Mar 19, 2006 | 07:03 PM
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PICS!!!!
 
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Old Mar 19, 2006 | 07:06 PM
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Since you asked about a tuner I assume you do not have one. Putting larger tires on a computer controlled truck and not informing the PCM will agravate the miles per gallon loss.
Unless you had the dealer adjust the speedometer your bigger tires will falsify the distance traveled, thus making your gas mileage seem even worse.

A 5 percent increase in diameter will probably drop your mileage 10% around town while making it report 5% worse than you are actually getting, thus showing you 15% worse than before.

On the freeway you may get half of that mileage drop back, but you will still have the speedo error.
Chris
 
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Old Mar 19, 2006 | 07:07 PM
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Xcal 2 you can tune it to your tire size..so it'll fix ur odometer
 
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Old Mar 19, 2006 | 07:25 PM
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ChrisAdams thanks for the bit of advice, I didn't even think about how the PCM would be affected.
 
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Old Mar 19, 2006 | 07:35 PM
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Originally Posted by ChrisAdams
Since you asked about a tuner I assume you do not have one. Putting larger tires on a computer controlled truck and not informing the PCM will agravate the miles per gallon loss.
Unless you had the dealer adjust the speedometer your bigger tires will falsify the distance traveled, thus making your gas mileage seem even worse.

A 5 percent increase in diameter will probably drop your mileage 10% around town while making it report 5% worse than you are actually getting, thus showing you 15% worse than before.

On the freeway you may get half of that mileage drop back, but you will still have the speedo error.
Chris
yea.. I was gonna say that...
I'm suprised it wasn't the first thing posted.
 
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Old Mar 19, 2006 | 07:40 PM
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Originally Posted by ChrisAdams
Putting larger tires on a computer controlled truck and not informing the PCM will agravate the miles per gallon loss.
This is true if he is pulling his mileage strictly from the trip/on-board computer and its a good point of clarification, how are you calculating your MPG?

The only thing that matters is hand calculated: trip meter (if your trip meter is accurate) divided by gallons filled at the pump. Using the on-board "your getting 14.2mpg" is not a good short-term accurate calculation.

Heavier tires and wheels will always cost you mileage, you expected that right? Your best best is to see how far off your trip meter is by using mile markers on the highway to determine if its off (or a GPS to compare speed and distance traveled). That should be your starting point for your baseline.
 
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Old Mar 19, 2006 | 07:52 PM
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Originally Posted by JerryK
This is true if he is pulling his mileage strictly from the trip/on-board computer and its a good point of clarification, how are you calculating your MPG?

The only thing that matters is hand calculated: trip meter (if your trip meter is accurate) divided by gallons filled at the pump. Using the on-board "your getting 14.2mpg" is not a good short-term accurate calculation.

Heavier tires and wheels will always cost you mileage, you expected that right? Your best best is to see how far off your trip meter is by using mile markers on the highway to determine if its off (or a GPS to compare speed and distance traveled). That should be your starting point for your baseline.
If he is doing the math, the larger tire size will throw his numbers off. It has nothing to do with the trip computer. When you increase the diameter of the tire the odometer and speedometer go off by the same amount.
In simple terms, if he increases the diameter by 5% the odometer will read 5% less. Example, he drives 200 miles on the trip/odometer and fills up. Because of the error he installed by putting larger tires on he has actually gone 210 miles. So if he got 20 miles to the gallon he would put in 10.5 gallons, while the odometer claims he only drove 200 miles.
Thus his actual mpg is 20; his calculated shows mileage shows 19 mpg.

So when you increase your tires and don't adjust the PCM you get
1. Tire weight increases, making it harder to start running.
2. Gearing up, making your mileage around town worse, highway possibly better.
3. PCM shifting the transmission at the wrong points as it gets all its speed info from the VSS which is getting WRONG info from the tires.
4. Odometer/trip odometer/speedometer/trip computer are off by the amount of the increase.
Thus the numbers seem to jump a lot, but appear to jump even more.
Oh yeah, and the possibility of getting a ticket because your going faster than you think you are.

Chris
 
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