Correct Gas Milage - Computer Dash Calculations OR Hand Calculations??

[Maximus Gladius]

8.5 is not correct. 13.33L/113.7km = 11.7L/100km not 8.5L/100km. It is an impressive 23mpg but the accuracy is suspect because of the short distance and small amount of fuel. Pumps don't shut off at the exact same fill level every time. A difference of just 1/2 liter would bring your fuel mileage down to 13.83L/100km = 19mpg. Still good but not 23 or 28.

For better accuracy you could try waiting 30 seconds after it clicks off then trying to fill it more. You will also get better accuracy if you do it over a complete tankful. For best accuracy you do it over multiple tankfuls, keeping track of the total mileage and total of all the fillups then dividing.

I find the tank-to-tank mpg calculations jump around a lot for no good reason other than the most likely cause of not filling to the exact same level each time, but they average out over time.

I can see a problem in filling to the exact level every time and which one is correct without “over filling” or filling the EVAP canister which can’t be good. When one pump clicks off could be different to another so the idea that several tanks should be run to get the more accurate number is the best idea.

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[Maximus Gladius]

Looks like my math was wrong!! I missed one step as was pointed out by others! LOL.

So it does just come out as 20 mpg! Awesome

*This was just a test to see if yall were on your game! Carry on…..

 

[Maximus Gladius]

So we did identify a couple of things..
1. I really can’t do math and;
2. The correct math shows 11.6L/100 when my dash reads 13.6/100.

 

[BlackRuby23]

My Gladiator is really difficult to actually fill up. When the pump clicks off, the tank is not full. If I continue to slowly fill it following that, I can get another 3+ gallons in. I don't know why this is. This makes it near impossible to hand calculate mileage.

 

[bill61]

I have an Excel sheet that I track mileage on. I take a picture of my odometer, the price at the pump, and the final cost and gallons. Over time you can get pretty accurate. I have every fill up of my JKU since I bought it in 2017 and all my fill ups for my Gladiator.
The JKU dash accuracy varies a mile or two from my spread sheet each fill up. I only have 2 fill ups so far on my JT.

 

[Hootbro]

I have always hand calculated mine at full tank at first click of the handle and repeat.

Below are my two Gladiator Rubicons (over 300+ fill-ups) as recorded on Fuelly all hand calculated. 17 ish MPG was my average running a 80/20 HWY/CTY mix on 35's.

2020 Gladiator Rubicon

https://www.fuelly.com/car/jeep/gladiator/2020/hootbro/930052

2022 Gladiator Rubicon

https://www.fuelly.com/car/jeep/gladiator/2022/hootbro/1158871

Edit: If you put the cursor over the note icon, that was what my EVIC display mileage was. On one of the two, I did do a CSV file download of my data and extracted that on average, my EVIC was like 0.6 MPG high vs. the hand calculation.

 

[Stan H]

Which one offers the “correct” gas mileage numbers?

I have the 21 JTR, 3.6, 114k kms/71k miles.
Most people, if not all, have posted screen shots of their gas/fuel mileage and some are happy while others …not happy and I’ve always relied on the dash calculations to tell me what my gas mileage is doing.

Maybe it’s been said a couple times on here that the most accurate way of knowing is to hand calculate. Start with a full tank, or first shut off at the pump. Then drive and fill up again to first shut off at the pump. [ miles/kms divided by gallons/litres = mpg/…L/100 kms.]

So, in my 114k kms, I’ve only been watching the dash calculations… until yesterday. I filled up, had a short highway trip out of Calgary for the day then back last night and filled up again and hand calculated.

During the 113.7 km trip, my dash was showing me 14.5 to finish out at 13.6L/100km (17 mpg). The trip there was mostly strong headwinds and coming back it was relatively calm.

I stopped at the gas station and filled up again and came home and sat down to figure it out.

I drove 113.7 kms/13.3L = 8.5L/100 or 27.6 mpg! My dash isn’t even close. Now the real test is to drive at least half a tank, in the winter I don’t want to go lower than that. So, what have I done maintenance wise, mod wise to get to these numbers?

1. I drive the same brick you all do.
2. Mods like rock sliders and 315/70/17 tires - dealership calibration done. GPS matches odometer. Mods and tools I cart around = 250 lbs.
3. I do use an octane boost (technically it doesn’t change the octane # like choosing different grades of gas at the pump, it’s a “power” boost and doesn’t contain the bad stuff our book says to avoid)
4. I replaced spark plugs back at 60k kms with OE.
5. I installed an oil catch can and capture 210-250mls oil at every 5000 km oil change. I’m no longer burning this oil.
6. Swapped out oxygen sensors for OE at 110k kms.
7. Changed out the ERG valve and recalibrated it a couple weeks back.
7. Performed an ECM relearn, throttle body relearn, transmission quick learn.

That’s pretty much it.

I just changed my O2 sensor today .. I will let you know going to drive 64.5 miles to work .
This is what the thing looked like .

 

[Maximus Gladius]

I just changed my O2 sensor today .. I will let you know going to drive 64.5 miles to work .
This is what the thing looked like .

I found this:
https://www.google.com/search?q=whi...sors&ie=UTF-8&oe=UTF-8&hl=en-ca&client=safari

Does any of this apply? Have you noticed coolant consumption?
[edit] I’m betting this is an upstream sensor in the photo? Do both upstream sensors look like this or just one side? The downstream shouldn’t look this way, right?

You could get an oil analysis done too to identify coolant internal leak or not.

 

[SC Notary]

We are in our seventh Jeep. Gas mileage concerns were gone after our CJ-5 in 1980.

 

[Labswine]

We are in our seventh Jeep. Gas mileage concerns were gone after our CJ-5 in 1980.

I use the fuel economy to make sure everything is working properly. If it suddenly drops significantly, there's a problem somewhere that needs to be addressed. Sometime issues crop up with no idiot lights flashing in your face from the instrument cluster.

 

[Y-Guy]

I use a app called Road Trip to track all my gas and vehicle expense. While I really don't care, it does show me if I am having an issue, I know the range I expect during the time of the year. My last fill up was just after a couple of weeks of bitter cold temps and snow. I ran my remote start a lot during that time, and MPG reflected it.

 

[Stan H]

I found this:
https://www.google.com/search?q=whi...sors&ie=UTF-8&oe=UTF-8&hl=en-ca&client=safari

Does any of this apply? Have you noticed coolant consumption?
[edit] I’m betting this is an upstream sensor in the photo? Do both upstream sensors look like this or just one side? The downstream shouldn’t look this way, right?

You could get an oil analysis done too to identify coolant internal leak or not.

No consumption .. I haven't done the other side upstream yet just the master upstream on bank 1. I will order the other 3 soon.
Yes that is my upstream bank 1 sensor

 

[Stan H]

I just changed my O2 sensor today .. I will let you know going to drive 64.5 miles to work .
This is what the thing looked like .

Here is what it was getting traveling and then 17.6 after whole trip.

 

[bgott]

Use your trip odometer to hand calculate. The big average meter on the range/current gauge will screw up your hand calculations, especially if your last tank was towing or climbing mountains, etc.

BlackRuby23, they are designed to have that air space in the tank after fill- up. Don’t top it up. The gas in the station’s underground tank is stored where it’s nice and cool. You then pump it up into your tank where it goes into a space that has been heated up over a nice, hot highway. The gas needs expansion space.

 

[brsnow2585]

I keep an eye on the average gauge more to figure when I need to stop or if I'm going to make it, the last 1/3 of the fuel gauge seems to go a lot quicker. I use the 2 trip meters, #1 reset every fill-up, #2 reset on oil change. '22 Rubicon diesel, steel bumpers, winch, Mopar lift, approaching 35k miles, stock wheels and tires, so I'm running heavier. I mostly watch the computer between tanks to watch for unexpected differences. I tow/haul on and off but know the numbers to expect. I've hand calculated on and off and they match up close enough that I'm not concerned. ~18-19mpg tow/haul, ~22-23mpg unloaded, been adding Lucas injector cleaner occasionally, that jumps it up to ~25-26mpg on that tank. Says it boosts the cetane, ~$5 per tank. Haven't done the hand calculations on that, kinda moving target with diesel prices swinging so wildly. Drove from Illinois to Texas a couple weeks ago, saw prices all over an 85 cent range, luckily only had to hit one of the really high ones.

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