Increasing MPG after installing lift and tires.

[Mountain Whiskey]

He thinks he's getting 10-11 MPG because his computer is programmed for 32" tires. I don't think anyone here is so dumb that they think recalibrating the speedometer will actually give you better fuel economy.

Hand calculating won't do him any good, because his odometer isn't accurate. In order for hand calculations to work, he would need to factor in the reduced revolutions per mile.

Yep. @Shots directed to the OP, I followed suit. I think most get it.

Good point on the hand calculation not working either. Well unless the old calculator works a little overtime. I'd have to take my socks off to keep that kind of count going!

 

[stevj]

Or he could slow down a bit.

Steve

 

[Ram12375]

Another way to look at it is you will be putting less miles on your truck if you do not recalibrate

 

[Shots]

....To improve milage:
1. If you tend to drive fast, drive slower.
2. Maintain proper air pressure in your tires.
3. Don't sit and idle too long, don't use remote start.
4. Make sure it is tuned up and running properly.

I'll add #5.
5. Don't drive up to traffic/intersections/etc and brake hard. I'm not saying to coast from a mile away, but the harder you're braking means you've wasted momentum and therefore fuel up to that point.
There is a whole thing on hyper-mileing. I'm not that guy and those people go to the extreme. At the same time there's no point in keeping rpm's up to maintain a speed that you're just going to slam on the brakes a few seconds later. Easy throttle, easy brake. That will give you the best efficiency.

He thinks he's getting 10-11 MPG because his computer is programmed for 32" tires. I don't think anyone here is so dumb that they think recalibrating the speedometer will actually give you better fuel economy.

Hand calculating won't do him any good, because his odometer isn't accurate. In order for hand calculations to work, he would need to factor in the reduced revolutions per mile.

I won't say anyone is "dumb" if they thought recalibrating the speedometer would improve mileage. I'd call them uninformed. If you don't know how it works and/or how it does calculations you're not dumb for not knowing. Which is why I pointed it out in the first place. I wasn't trying to imply anyone was unintelligent. Only that they simply may not have known, and therefore made a false assumption (OP or anyone else reading the thread).
There's a big difference between unintelligent and uneducated.
Washoe (a chimpanzee) was taught sign language in the '60s-'70s. She wasn't some genius level chimp, just a common primate. She knew something the other chimps didn't, which doesn't mean they were dumb/unintelligent. That just means the other chimps were uneducated.
The same holds true here. If you don't know the adjustment won't effect efficiency you could make an incorrect assumption. That doesn't make you "dumb" because you didn't know what someone else knew.
I would never say or imply that.

As for hand calculating. Yes you would have to account for the odometer error in your calculations too, as you noted. It can be done. It would be a pain, but not difficult. Just extra work. However, doing the extra math for a few weeks to figure out a true loss from the modification may make the OP happier about the mod.

 

[Idahoktm]

I won't say anyone is "dumb" if they thought recalibrating the speedometer would improve mileage. I'd call them uninformed. If you don't know how it works and/or how it does calculations you're not dumb for not knowing. Which is why I pointed it out in the first place. I wasn't trying to imply anyone was unintelligent. Only that they simply may not have known, and therefore made a false assumption (OP or anyone else reading the thread).
There's a big difference between unintelligent and uneducated.

As for hand calculating. Yes you would have to account for the odometer error in your calculations too, as you noted. It can be done. It would be a pain, but not difficult. Just extra work. However, doing the extra math for a few weeks to figure out a true loss from the modification may make the OP happier about the mod.

Dumb, as in a few of you thought I was an idiot for my first comment. The and follow up posts made me realize a few of you misunderstood what I posted, but I clarified in my next post.

As for the recalibration being worth it. It was an easy decision for me. I don't like having to do the math to figure out how fast I'm really going. The fuel computer is accurate for MPG and range. Some say it effects the shift points. It's so much easier to program a speedometer today than it was with mechanical speedometers, so why not? I also wanted to change a few settings like fog lamp dropout, tailgate ajar, off-road pages, etc.

 

[Mountain Whiskey]

Sooooo, Shots, I guess your not saying someone is dumb but just smart as a chimp. OK, makes sense to me! Way more polite.

 

[Shots]

Sooooo, Shots, I guess your not saying someone is dumb but just smart as a chimp. OK, makes sense to me! Way more polite.

LOL
Well since I don't know ASL, I guess a chimp is smarter than me too, so there's that.

 

[Shots]

Dumb, as in a few of you thought I was an idiot for my first comment. The and follow up posts made me realize a few of you misunderstood what I posted, but I clarified in my next post.

As for the recalibration being worth it. It was an easy decision for me. I don't like having to do the math to figure out how fast I'm really going. The fuel computer is accurate for MPG and range. Some say it effects the shift points. It's so much easier to program a speedometer today than it was with mechanical speedometers, so why not? I also wanted to change a few settings like fog lamp dropout, tailgate ajar, off-road pages, etc.

I agree with reprogramming it too. I wonder about shift points but that depends on how the PCM is programmed. But like you said, it's not hard to do, so you might as well.

And for clarification, I didn't assume you meant it would affect efficiency, I was just making sure the OP and/or other people who stumbled onto the thread didn't take it that way. I can see where it got confused though.

 

[Scram1500]

Another way to look at it is you will be putting less miles on your truck if you do not recalibrate

Which could technically be considered a felony

THE FEDERAL ODOMETER TAMPERING STATUTES

www.justice.gov

 

[theblet]

Which could technically be considered a felony

THE FEDERAL ODOMETER TAMPERING STATUTES

www.justice.gov

It’s only a crime if you get caught

 

[Ram12375]

Which could technically be considered a felony

THE FEDERAL ODOMETER TAMPERING STATUTES

www.justice.gov

Not recalibrating after changing tire size is a felony?

 

[theblet]

Not recalibrating after changing tire size is a felony?

Tampering with the odometer is, not tampering with the tires.

 

[ahallag88]

Seems like a pretty easy choice to me.

OP, just to be clear about the whole computer adjustment thing. This isn't actually improving your efficiency, it's just accurately reporting the mileage so your calculations are accurate instead of reading lower than what you're actually getting. You'll still be using the same amount of fuel.

Correct. I understood that it would just give me an accurate reading.

 

[Shots]

Not recalibrating after changing tire size is a felony?

Tampering with the odometer is, not tampering with the tires.

Obviously it depends on each state what is considered odometer tampering but here in Ohio:

4549.42(A) No person shall adjust, alter, change, tamper with, advance, set back, disconnect, or fail to connect, an odometer of a motor vehicle, or cause any of the foregoing to occur to an odometer of a motor vehicle with the intent to alter the number of miles registered on the odometer.

There are two key pieces I see in our law which need attention.
1. "No person shall... ...tamper with... ...an odomoter.... ....or cause any of the foregoing to occur..."
By changing the tire size without adjusting the odometer you have caused tampering to occur because the truck is logging less miles than are being driven. So you may not have directly tampered with the odometer, but you have "cased the foregoing to occur."
2. "....with the intent to alter the number of miles registered on the odometer."
This is important too. Maybe even more so. Although the modification may have caused tampering to occur, Ohio requires intent for it to be a felony. If you're changing the tire size because you like the look, or feel you need bigger tires and you fail to reprogram the computer to the correct size because you didn't know it effected the odometer, or because you simply didn't want to spend the money, that isn't intent to tamper with the odometer. That's doing a modification with an unintended result. If you're changing the tires and not reprogramming the computer with the purpose of logging fewer miles, that is a felony.

I suspect it would be extremely hard to prove intent, but I'm no attorney.

 

[Shots]

Interestingly though the US code doesn't list that intent:

"49 U.S.C. § 32703(2). A person may not— (1) advertise for sale, sell, use, install, or have installed, a device that makes an odometer of a motor vehicle register a mileage different from the mileage the vehicle was driven, as registered by the odometer within the designed tolerance of the manufacturer of the odometer;"

"A person may not... ...install, or have installed, a device that makes an odometer... ...register a mileage different from the mileage the vehicle was driven."
Oversize tires without reprograming is a "device" which would cause the truck to read less miles. So technically sounds like it fits the federal prohibition.

 

[OCD Solutions]

If that were the case, tire dealers would be required to adjust the odometer or become accessories to a felon?

 

[Lpsouth1978]

OP, I would just get AlfaOBD and correct the tire size. It is VERY easy and corrects the Odometer, speedometer, and MPG calculations. You will then also be able to change a number of additional things. For example, on my RAM, I changed the running lights to the amber turn signals (looks SOOO much better), enabled the Off-road pages, and turned on the tailgate ajar warning.

On another note, I did a 3"front/2" rear lift/level and have 35" Yokohama Geolandar A/T G015 295/65r20 tires. My MPG averages 15.5-16.5 with mostly in town driving to/from work.

 

[Shots]

If that were the case, tire dealers would be required to adjust the odometer or become accessories to a felon?

Good question. Do they get a loop hole by saying they assume the owner will have it adjusted? Similar to tint companies claiming they assume the 5% tint they install on all the windows (including the windshield) will be used off road only. How about the shop that lifts a truck so high it exceeds the legal bumper heights? Companies make modifications to vehicles all the time that are illegal, and somehow aren't considered accessories to it. Or maybe they are, and nobody pursues it.

Who know, but that's a good question.

 

[theblet]

Good question. Do they get a loop hole by saying they assume the owner will have it adjusted? Similar to tint companies claiming they assume the 5% tint they install on all the windows (including the windshield) will be used off road only. How about the shop that lifts a truck so high it exceeds the legal bumper heights? Companies make modifications to vehicles all the time that are illegal, and somehow aren't considered accessories to it. Or maybe they are, and nobody pursues it.

Who know, but that's a good question.

There’s probably a clause when you sign your vehicle paperwork that absolves them of any liability. Lawyers are lawyers for a reason

 

[Shots]

No doubt, and they know very few people actually read it all.