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DTE Accuracy

Old 11-02-2018, 05:33 PM
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Default DTE Accuracy

I have read about the superduty DTE being inaccurate for those of us with long beds and the 35 gal. gas tank. My question is the MPG reading is off as well. Normally it reads about 8% too high. It will read 10 but hand calculates 9.2! Is this error also due to the DTE problem? My friend has a 2015 6.7 short bed with the smaller tank and his MPG is accurate.
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Old 11-05-2018, 07:35 PM
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The DTE is a function of the computer, MPG and speedometer/odometer working in unison. The problem (not Ford Super Duty specific) is that if the MPG is off at all, so is your DTE. This happens due to a speedometer/odometer being off. It's a snowball effect. And, it doesn't take much to be off.

I've found my MPG to be off by about 7% as well in my F250. The fuel tank always takes a bit more than the "gallons used" number and the truck's MPG is always a bit higher than hand calculated. Now, I've only had the F250 for 6 weeks but noticed this with each fill up so far.

My F150 was like that as well. When I first got it, the DTE and MPG was off significantly. When I went from 32" to 33" tires, everything straightened out......with one change. I wanted to make sure my speedometer was accurate so I got a Hypertech speedometer calibrator. Testing the speedometer against a handheld GPS and my cell phone GPS, I was able to dial in 60mph for 60mph. Low and behold, every fill up after that, the computer and MPG was remarkably accurate.

I would bet, there's a bit of tolerance at the Ford plant for speedometer accuracy. You have to figure these trucks can come with tires that measure from 31.5" to 33.4" in diameter and that alone will throw the speedometer off a lot.
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