MPG indicator question.....
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New User
Joined: Oct 2010
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MPG indicator question.....
We got an excursion that is lifted with 40 inch tires. This bad boy is a beast!! We noticed on the built in MPG indication, that according to that, we are only getting 4-8 mpg driving around town. My question is, a) does having a lift with 40 inch tires hurt your mpg....and b) is it possible that the indicator is just way off? 4 mpg seems pretty extreme.
Here's a picture of our little girl next to it....
Here's a picture of our little girl next to it....
Thread Starter
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New User
Joined: Oct 2010
Posts: 5
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When we get up to about 20, we are really going 30 mph. So its off by about 10. Sorry, i'm Eran's wife who posted this questions, and so I don't know alot about this stuff. Does it calculate it wrong if the speedometer is off?
Thanks for your patience with my lack of knowledge about all of this!
Thanks for your patience with my lack of knowledge about all of this!
More Turbo
Joined: Jan 2009
Posts: 530
Likes: 2
From: LI, NY
There are a few things going on...
A 40" tire rolls a lot further for each revolution than the stock 32" tires. The speedometer & MGP calculator do not know about the big tires, so they are off by 40/32. You go 25% further than shown. Your actual MPG is also 25% higher than indicated.
The new tires are heavy making it harder to accelerate.
The tires are wide, so more rolling resistance.
The differential gear ratio was chosen for 32" tires, it's harder to accelerate now. Like starting in 2nd gear.
But you effectively have a huge overdrive ratio, as reflected in ford2000ex's post.
A 40" tire rolls a lot further for each revolution than the stock 32" tires. The speedometer & MGP calculator do not know about the big tires, so they are off by 40/32. You go 25% further than shown. Your actual MPG is also 25% higher than indicated.
The new tires are heavy making it harder to accelerate.
The tires are wide, so more rolling resistance.
The differential gear ratio was chosen for 32" tires, it's harder to accelerate now. Like starting in 2nd gear.
But you effectively have a huge overdrive ratio, as reflected in ford2000ex's post.
