13.1mpg best I can get with 35’s. Questions inside…..

[Aonarch]

From the manual

CAUTION!

DO NOT use E-85, gasoline containing methanol, or gasoline containing more than 15% ethanol (E-15). Use of these blends may result in starting and drivability problems, damage critical fuel system components, cause emissions to exceed the applicable standard, and/or cause the Malfunction Indicator Light to illuminate. Please observe pump labels as they should clearly communicate if a fuel contains greater than 15% ethanol (E-15).

I am tuned for E-85.

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[dcmdon]

I find it ironic that people want huge heavy tires and wheels - then even think about mpg.
Sorry, but they are pretty much contradictory. There's a reason Jeep puts on the tires they do - CAFE and MPG - any variation from that will impact MPG negatively. 35 are bad mpg and then going to 37s?

Unsprung weight is bad for suspension and steering and heavier tires and wheels impact braking in a negative way - and for sure mpg. It's really pretty simple.

As far as mpg calculations - make sure to use an independent GPS to verify tire size input.
Don't go by measurements or what others may say to put in.
Plug in the numbers - and then verify with a GPS!
Very possible it's still wrong if you haven't actually driven a few miles and compared odometer to GPS readings.

While he's at it, he should use a GPS to measure the distance he travels when testing MPG.

If the tire size is off, the odometer will be off. So even he calculates MPG the old fashioned way (dividing the miles traveled by the gas the truck takes when you top it off) it will be off if the odometer is off.

I don't expect to get very good mileage with my Gladiator mainly because during the week its in an urban environment. My current car has an EPA combined rating of 24 mpg and I get 18 with it.

When I am up in NH with it, I average about 26.

 

[dcmdon]

I am tuned for E-85.

You do realize that you will get about 30% worse miles per gallon with E85, right?

My nephew has a hot rodded Golf R. When he runs normal gas he gets 300+ miles per tank. When he runs e85 he gets about 230 miles.

Alcohol has much less energy per gallon. So more is needed. Most high performance E85 kits include larger injectors because of the need to flow more fuel.

The fact that alcohol has much higher octane and allows more ignition advance doesn't even begin to make up for the lower energy per gallon.

 

[Aonarch]

You do realize that you will get about 30% worse miles per gallon with E85, right?

My nephew has a hot rodded Golf R. When he runs normal gas he gets 300+ miles per tank. When he runs e85 he gets about 230 miles.

Alcohol has much less energy per gallon. So more is needed. Most high performance E85 kits include larger injectors because of the need to flow more fuel.

The fact that alcohol has much higher octane and allows more ignition advance doesn't even begin to make up for the lower energy per gallon.

Who said I care about MPG?

I've been running E-85 since 07-08.

 

[dcmdon]

Who said I care about MPG?

I've been running E-85 since 07-08.

Its just important for people to know if they are considering using it.

How much per gallon does it cost you? In the northeast its expensive but I've heard that in the midwest it can be reasonable. I don't actually know numbers. My nephew just says its expensive.

 

[Aonarch]

Its just important for people to know if they are considering using it.

How much per gallon does it cost you? In the northeast its expensive but I've heard that in the midwest it can be reasonable. I don't actually know numbers. My nephew just says its expensive.

It's a dollar cheaper than 93 here.

In the corn belt it's super cheap.

E-85 gives great power, smoothness, and runs cooler.

 

[ShadowsPapa]

While he's at it, he should use a GPS to measure the distance he travels when testing MPG.

If the tire size is off, the odometer will be off. So even he calculates MPG the old fashioned way (dividing the miles traveled by the gas the truck takes when you top it off) it will be off if the odometer is off.

I don't expect to get very good mileage with my Gladiator mainly because during the week its in an urban environment. My current car has an EPA combined rating of 24 mpg and I get 18 with it.

When I am up in NH with it, I average about 26.

Yeah that's what i said. Compare odometer on truck to gps miles driven.

 

[Gren71]

When I was building mine I put a lot of thought into the front bumper as well. I noticed they had these on mine,

I removed them and rode around without them on the jeep before I decided on a front bumper and noticed my Mpgs started dropping ever so slightly a little bit every couple days. I couldn't keep it steady

I also noticed most of the people complaining about Mpgs didn't have that piece leading up from the bumper to the fenders, so I figured they probably put that on to help with Mpgs and I also saw that only Max Tows from what I could tell came with it, which would make sense to help with Mpgs while towing. I assume keeping air from flowing directly into the wheel wells and pushing it around them would be more aerodynamic so I made a decision to choose a full width bumper and one that would fill that gap back in. That was some the reason I chose the bumper I have and the fact that it only weighs 80lbs and the winch only weighs like 80lbs as well.

I'm not saying that this is totally what is helping me, it probably has to do with driving habits some as well as me letting the start/stop do what it's supposed to. I baby mine and am rarely over 75mph in it. Also wheel and tire weight, I particularly wanted the steel black wheels so I wouldn't want to swap them so I could stay on the lighter side and I chose one of the lightest 37's you can buy, not many out there that jeep the weight under 75lbs, mine are 72lbs a piece and I think the wheel weighs around 26lbs.

I could be just over thinking all of it but it seems to be working for me. I got another buddy who has 5aken this approach on his JL when I told him what I did and he has been able to gain a few Mpgs as well.

Ive always wondered of those air dams would make more an issue after a lift. Since a lift creates a small gap at the top of the dam. I still have my JTMT front bumper and have occasionally considered throwing it back on to see.

 

[ShadowsPapa]

Ive always wondered of those air dams would make more an issue after a lift. Since a lift creates a small gap at the top of the dam. I still have my JTMT front bumper and have occasionally considered throwing it back on to see.

How would a lift create a gap?
A lift drops the axle down, or pushes the frame up, however you want to look at it.
The air dam is connected to the bumper. The bumper is solidly bolted to the frame. The body is attached to the frame. The relationship between frame and body is not changed. The relationship between axle and body is changed.
You can drop the axle clear down a foot with a lift and it won't change the frame-to-body measurements.

Only changing fenders would change that.

 

[ShadowsPapa]

Its just important for people to know if they are considering using it.

How much per gallon does it cost you? In the northeast its expensive but I've heard that in the midwest it can be reasonable. I don't actually know numbers. My nephew just says its expensive.

It's not something they can simply start using anyway.

Even if it was, say that Jeep had "flex fuel" vehicles that could use it, it's a LOT cheaper in some cases, a fair amount cheaper in others.
The guy I got my Silverado from years ago said he kept a small spreadsheet and it had the typical difference in mpg he got with his truck and he could plug in the current E85 price vs other gasolines and it would tell him where the break-even point was - at which point would the degrease in mpg offset the big cost/gallon difference. He said at times when gas was really cheap it didn't pay in economy but then he got more power with E85 for towing so he'd sometimes use it anyway for the extra 20 hp or so he got with it.

I used it in my own Chevy and realized the extra hp when towing especially on the hills here in Iowa - on east I80 it made a difference.

Right now the price spread varies from about 3% to 39% depending on state, station and so on. In other words, you can find E85 a dollar or more cheaper than E10 or straight gas.
At those rates, E85 saves you even with the lower mpg.

In Iowa it's a range from 3% to 17% depending on location and station.
I've seen it a bit cheaper than $2.69 myself but here's one example of the current spread -

E85 straight gas percentage spread E15 gas
$2.69 $3.23 17% E15:$3.04
Kwik Star, 3205 Willow Creek Ct Clear Lake IA

 

[NachoRuby]

Its just important for people to know if they are considering using it.

How much per gallon does it cost you? In the northeast its expensive but I've heard that in the midwest it can be reasonable. I don't actually know numbers. My nephew just says its expensive.

E85 is pretty cheap here too (Pennsylvania). I'd tune for it, but I want to keep my powertrain warranty. Once I hit 60k, I'll probably get tuned too. Sometimes I run e15, because it's also much cheaper here, to the point that it offsets the mpg hit. I lose maybe 1 mpg on e15 compared to normal gasoline which is e10 here where I live. E15 is warranty safe, though.

 

[Gren71]

How would a lift create a gap?
A lift drops the axle down, or pushes the frame up, however you want to look at it.
The air dam is connected to the bumper. The bumper is solidly bolted to the frame. The body is attached to the frame. The relationship between frame and body is not changed. The relationship between axle and body is changed.
You can drop the axle clear down a foot with a lift and it won't change the frame-to-body measurements.

Only changing fenders would change that.

?? Just noticed a gap after the lift. Couldn’t explain it.

 

[AP Double]

I'm running 37's on mine, Kanti trail hogs, they weigh about 72lbs a piece with stock wheels and about 3-1/4 inches of lift. Max Tow with 4.10 gears I average 17-17.2 normally total mix of about 50/50 Hwy City driving. Got over 18 on our last couple trips to the beach and mountains. I live in the Piedmont area of North Carolina and there are rolling hills around here.

Video was when I was running 37 12.5 17 Goodyear kevlar MTRs

Mine as it currently sits, I also let the Auto start stop do it's thing, I never turn it off and utilize it when I can. You will be surprised at the Mpgs you can save by using it like your suppose to, these things really drink has for some reason when sitting idle.

This is super helpful. Do you know what those stock wheels weigh? I’m pretty sure that these are the wheels coming on my JT (on order). I was thinking about putting 35’s on them but also wondering if it’s okay to put a 12.5” wide tire on these stock wheels, which I think are 7.5” wide. Have you had any issues with that? Any crowning at full highway air pressure?

 

[Jeeperjamie]

This is super helpful. Do you know what those stock wheels weigh? I’m pretty sure that these are the wheels coming on my JT (on order). I was thinking about putting 35’s on them but also wondering if it’s okay to put a 12.5” wide tire on these stock wheels, which I think are 7.5” wide. Have you had any issues with that? Any crowning at full highway air pressure?

No, no crowning and these are my second set of 37 12.5 17 tires I've had on them. I was running Goodyear Kevlar MTRs before. Got about 4,000 miles on the Kanati's and they are wearing evenly so far and look like they are brand new still. I run 33lbs of pressure in them which seems to be the sweat spot and was the same pressure I ran in the Goodyear MTRs as well. I'm pretty sure the stock steel wheels weigh right at 26lbs a piece.

 

[Jeeperjamie]

@AP Double here's a spec sheet from DISCOUNT TIRE that gives you a idea of what can be mounted on different size wheels as far as tire size and width.

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