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Discussion Starter · #1 ·
I recently started using Fuelly again, after a several year break. I was curious how the indicated MPG on the Sienna display compared to actual MPG from calculating on fuel-ups, so when recording in Fuelly, I added notes for the indicated MPG, and started resetting the indicated MPG at each fuel up. I'm only 4 fuel ups in, but this is what it looks like so far:


Currently, I've been doing a lot more highway driving than I have been, with some 45 mile commutes that are mostly highway and/or freeway. 60 MPH if I take the highway route, 75 MPH if I take the freeway route.

2014 Sienna LE with 122,500 miles, with new spark plugs a couple thousand miles ago. Running new Michelin CrossClimate2 tires.
 

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Discussion Starter · #5 · (Edited)
Yes, I have been noticing this (typically) 5% difference, and I remember seeing the same deviation on the Prius as well. So we could conclude it's not a Sienna thing, and not a hybrid thing; it's a Toyota thing.

BTW, is it some kind of a welding apparatus that you have in the cubby on the rear left?
Not just Toyota. My Honda Pilot over-reported roughly the same if I remember correctly, but while I tracked much driving in the Pilot on Fuelly, I didn’t track indicated MPG vs actual.

And no, not welding. There’s a first aid kit, a 5 pound ABC fire extinguisher, some shopping bags, and a set of very crappy jumper cables I once found on the side of the road.

My plan is to mount a vehicle fire extinguisher bracket, which I have. To mount this, I plan to pull back the plastic and bolt in a simple metal bracket behind the plastic, that I can bolt the fire extinguisher bracket to, so the fire extinguisher is securely fastened and not just sitting there loose.

Eventually the van will be converted into a campervan, but I wanted to carry a fire extinguisher regardless of if it is a campervan or not. You never know when you might need it, either for your own vehicle or someone else’s.
 

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Discussion Starter · #8 · (Edited)
If you do cumulative mpgs over multiple tanks, the difference closes significantly.
Do you mean the difference in the dashboard indicated average MPG, or MPG between tanks? The first seems unlikely, the latter, well, I'm not certain the difference closes, there can be a lot of variation between different fill-ups, depending on many factors. Predominately how much highway/vs city driving.

You really need at least 3 or more tanks to get a true idea of mpg.

Also you need to consistently fill to the same level in the tank each time.
You mean like this? 66,818 miles tracked, with 227 fuel-ups. ;)


Or this? 20,184 miles tracked, 124 fuel-ups.


Additionally, I have 8172 miles tracked on a 2007 Honda Accord, 13,979 miles tracked on a 2004 GMC Envoy, and 50,300 miles tracked on a 2013 Honda Pilot. For all vehicles, I believe I tracked the entire time I owned that vehicle, unless I forgot to log a tank (rarely). When we sold the Honda Pilot and I bought my 2020 Chevy Silverado, I decided to not track MPG. Put 42,000 miles on that, sold it, and bought the Sienna. I didn't track that initially, so I'm just starting back into tracking MPG now, but I'm certainly not new at MPG tracking.

This thread in particular was mostly about tracking the differences between vehicle displayed MPG vs actual MPG calculated from fuel-ups.

I always fill my tank until the fuel pump shuts off. I don't "top up", the only time I manually add more is the rare occasions a fuel pump auto-sutoff isn't working right and shuts off way too early.

Well, one more exception to that, and that's my motorcycle. The nozzle doesn't sit in the tank, you have to hold it, and trying to use auto fill-up doesn't work great cause the gas foaming shuts the pump off WAY too early. So on my motorcycles, I've always filled up manually until the gas level touches the neck of the tank opening. That's probably much more consistent than filling any of my automobiles. I still own that motorcycle I pictured the fuel-ups from, but it hasn't been ridden in a long time, except for a couple of moves. I'm going to be getting back into riding that this spring, and yes
 

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Discussion Starter · #12 ·
I wonder if it would be different if the fuelly app could connect to the obd to measure fuel coming out of the injectors.

Or Just take the indicated readings and take away about 1mpg. The fuel tank/vapor recovery system is like filling up a balloon. The ECU doesn't have all of the variables to correct for that. It thinks it's using less gas than what you are putting in.

Measuring the fuel coming out of the injectors is what the ECU is already doing, so I'm not sure how the fuelly app would do it differently? (or rather, it's counting the time the injectors are open I believe)

In any case, I don't have the Fuelly app. I just text Fuelly. The text format is <shortcut code> <miles> <price> <gallons> <comments. For example, my latest fuel up I sent Fuelly this text message:
T 122419 2.869 15.892 22.4 MPG indicated. Kwik Trip 88 octane 15%. 10% was 3.249.
Where T is the shortcut letter I chose for my Sienna, and 122419 was my current odometer reading. All Fuelly does is divide miles driven on the tank by the gallons filled, which is easy enough to do by hand but more convenient to use Fuelly cause then it's logged and available for quick viewing.

After sending the above text message, Fuelly replied back with this text message:
Fuel-up Added! MPG: 22.1, Avg MPG: 21.2 Best tank so far! More stats on Fuelly: <link to my Sienna page on fuelly>
This shows up on my Fuelly account like this:
Rectangle Font Parallel Screenshot Circle


The first entry is blank because I decided to use odometer tracking this time, instead of trip odometer. Previously I used trip odometer, in which case you simply send the miles on that tank instead of odometer reading. You can configure you choice per vehicle.

In your Sienna, is this rectangular recess (where the extinguisher et al sit) the original storage cubby for the middle-middle-seat, with a further/deeper recess for the tire repair kit? Because in the 2021+ Sienna w/o the factory-installed spare, it would be :)
It is for the 8th seat, yes, as I have an 8-passenger van. I don't believe there is a further/deeper recess. I have a FWD van, not AWD, so I have a doughnut spare tire mounted under the van, and no tire repair kit. Just the typical cheap lug wrench and scissor jack, plug a strap for securing the full-sized damaged tire in the cargo area behind the third row, so it can't fly around if you get in an accident (a full size spare cannot fit under the van, so if you use the spare from under the van you have to carry the original tire in your passenger compartment). These items are located on the passenger side of the van, in the rear, behind a removable slotted panel that's also the air inlet to the rear HVAC blower unit.
 

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Discussion Starter · #14 ·
that is quite unfortunate... LOL.

let's face it, these are basically heavy SUVs, they are not made to get good MPGs. Plus, it looks like you have some additional equipment, which it fine, but really negating the seat removal. It is what it is. But without a doubt, the computer will ALWAYS produce "false positive" MPGs. It is only positive results for the manufacturer . It is only there to make you feel better, when the results are far less. I understand you know this is true.
Well the seats are probably 150 lbs. Currently I may have like less than 50 pounds of stuff. I'm not too concerned about MPG. It's going to go down when I build my campervan, between stuff on the roof adding air drag and hundreds of pounds of extra weight.
 

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Discussion Starter · #17 ·
My 2013 XLE came with the standard 235/60R17 tire size which when doing a highway mileage marker test indicated 1 mile on the odometer at the .9 mile road marker. As far as I know Toyota MPG stats are based on the odometer reading which obviously is incorrect. Speedometer was also off.
A couple of years ago I replced the OEM tires with 235/65R17's, a taller tire, which is spot on with the highway mileage markers. Unfortunately, as you probably guessed, my MPG dropped about 10%.
To answer the question which I'm sure I'll get on whether the taller tires rub or not, the answer is that when the steering wheel is totally turned to the left or the right (locked out) there is a very slight rub that can be heard.
That’s interesting. Usually odometer readings are much closer than that.

Have you tried using the trip odometer vs GPS over say a ten or twenty mile distance?

I do have stock 235/60R17 tires. I will check the odometer accuracy. I haven’t checked that yet. But, what I have checked is that while the speedometer is off, reading high with the stock tires, it is lying. The OBD speed, read using a scan tool, is essentially spot on with the GPS speed read by the phone running the scan tool! So the van seems to know the actual speed I’m driving, and displays a speed slightly higher than that.
 
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