Tires, Gears, and MPG

[Jeeperjamie]

Yes, tested against 2 GPS apps and several roadside speed-checker stations.

When I shopped for my wheel/tire combo, I specifically searched for the lightest setup I could find in my budget. I don't recall exact #s but my new wheel/tire combo is +-3 pounds from stock. I'm sure this is helping my situation.

I'm running my stock wheels which are lighter than pretty much any after market ones. Also my Kanati's are about the same weight as the BFG KO2s your running, yours are 71 lbs a piece, mine are 72. That's not going to make a 2 or 3 mpg difference. I baby mine as well. If this is true you would be getting better Mpgs than one running stock wheels almost and be on 37's? How's that possible?

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[JD101]

I live in Michigan, fall temps , pretty flat , low elevation .
37x12.50 stt pro ,4.10s drove great , but maybe saw 16-17mpg on road trips at 70mph. 8th was barely used , 7th pretty much always . 2" front and 1.5" rear . Stubby bumper and fender chop , tazer speedo corrected .

5.13 . Everything drivability was improved even over stock. 8th always Mpg up to 17-18.

Current : winter gas and cold temps .
38x13.50 trail graps . 4" f , 2" r . 5.13s
City 11.8-12 , hwy (70mph) 14 maybe 15 .8th always . Tazer speedo corrected .

Stock 2000 mile road trip to upstate NY from MI . Fall temps , 33s , 4.10 ,70-75mph . 19.8 ave overall .

 

[Gren71]

Not like that. I'm not buying it.

I was getting 23-24 w/2in lift and stock tires and just dropped to barely 20 when i put on my soft top.

 

[Jeeperjamie]

I was getting 23-24 w/2in lift and stock tires and just dropped to barely 20 when i put on my soft top.

Yeah I know, 22 on 37's seems a little out there. I can buy maybe 19 on a long trip because we got 18.5 on a 8 hour round trip to the beach in back. I mean I guess anything's possible. I'd love to see a 10 minute video of the speedo showing the average Mpgs on the interstate as he is driving. Pictures are tough to go by.

 

[kw_rc]

I updated the post with the final numbers for the round trip and included the refuel. This allowed me to get the actual MPGs for the trip.

 

[kw_rc]

I'm running my stock wheels which are lighter than pretty much any after market ones. Also my Kanati's are about the same weight as the BFG KO2s your running, yours are 71 lbs a piece, mine are 72. That's not going to make a 2 or 3 mpg difference. I baby mine as well. If this is true you would be getting better Mpgs than one running stock wheels almost and be on 37's? How's that possible?

I wish I would have refueled once I got into Austin. I decided to see what the actual MPG was for the trip. I updated the post with the info.

 

[Gvsukids]

Not sure what you mean. I checked it on the highway. So it was probably between 60-70 mph.

As these are bricks, that speed is optimal.

 

[Josh00333]

Nice then! I’m jealous!

 

[bakobobby]

I like to read these numbers gives perspective. I have 37” tires 4.5” (more like 5”) lift and 5.13 gearing. Also tore off all the wind deflecting stuff so streamlining is non-existant. Lately in town seeing around 13-14 mpg. Was seeing 1-2 mpg more just a few weeks ago wanna say the gas maybe has changed and is giving less miles. All I can think of. Think best I have seen is maybe 17.5ish when I mostly was on the highway but have to stick to around 65mph were I am turning just over 2000rpm.

 

[bakobobby]

I was getting 23-24 w/2in lift and stock tires and just dropped to barely 20 when i put on my soft top.

That is interesting because it makes me think lift may not have as much influence on mpg as I expect. Do you still have the wind deflectors for the bumpers and fenders? Soft top maybe adds a good deal of drag? I wonder how much springs and shocks factor in. I am going to try running a tank on firm mode for my Falcon 3.5s then a tank on soft. My springs are supposed to be pretty soft compared to stock sport springs.

 

[Gren71]

That is interesting because it makes me think lift may not have as much influence on mpg as I expect. Do you still have the wind deflectors for the bumpers and fenders? Soft top maybe adds a good deal of drag? I wonder how much springs and shocks factor in. I am going to try running a tank on firm mode for my Falcon 3.5s then a tank on soft. My springs are supposed to be pretty soft compared to stock sport springs.

I do. To be fair I had JUST had my rear diff replaced under warranty so It was likely breaking it. ive put nearly 1,000 miles on since then and the MPG is starting to come back. For instance I followed my own experiment parameters today and got 23.4mpg for my drive to work. My truck average is currently 21.6mpg. That is with the soft top and the bumper wind deflectors. The lift certainly makes a difference. But I think the rake makes more of a difference than just having a lift. Thats just a belief and I have nothing to back that up, but my $0.02.

If your going to do an experiment Id just suggest doing your best to isolate as many variables as you can. weather, road traveled, driving style (use cruise control), distance measured, ect. If you can isolate more variables, it lends weight to your finding.

 

[bakobobby]

If your going to do an experiment Id just suggest doing your best to isolate as many variables as you can. weather, road traveled, driving style (use cruise control), distance measured, ect. If you can isolate more variables, it lends weight to your finding.

Makes sense. Luckily the weather here is about to go into 6 months of hot heat and sunshine. I have a pretty good loop I can do almost all in cruise control with some big uphill and downhill in it. About 100ish miles. I fill up at the same Costco always.

To be fair I had JUST had my rear diff replaced under warranty so It was likely breaking it. ive put nearly 1,000 miles on since then and the MPG is starting to come back.

Interesting if that is a thing I too may see some better mpg once I work in the 5.13s. Sitting around 750 miles. Drained and filled the diffs at about 500 after the gear swap too. Been babying them. I also have some issues with my transmission and I wonder if that could cause some loss of mpg. Basically its been slipping and has a tcc shudder going too now. Going into the shop Tuesday. Hoping the techs just did a poor job and didn’t put in enough fluid on set up.

 

[Gren71]

Interesting if that is a thing I too may see some better mpg once I work in the 5.13s. Sitting around 750 miles. Drained and filled the diffs at about 500 after the gear swap too. Been babying them. I also have some issues with my transmission and I wonder if that could cause some loss of mpg. Basically its been slipping and has a tcc shudder going too now. Going into the shop Tuesday. Hoping the techs just did a poor job and didn’t put in enough fluid on set up.

very possible that the trans issue could be part of the problem. Its one of those things that you wont really know until all the work is done and broken back in. For instance I was assured by my shop that there was no break in period for my rear dif, and that the oil didnt need to be changed until my next oil change. Im willing to believe that since that essentially how it happens from the factory. But ive certainly noticed the difference with the parts breaking in more.

over all ive learned that a handful of things really make a difference.
1 ) driving style (distance / lead foot / hill vs flat / ect)
2 ) tires (size and tread)
3 ) aerodynamics (crazy front bumpers w/winches, bed racks, ect.)

We all know that theyre not gas sippers. But there are things we can do to maintain better performance and MPG for sure. Everyone is different and wants different things. I personally enjoy 20+ mpg and the ability to tow, combined with beach driving and doors off. Others love their rock crawling. Each build will have its good and bads.

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