MPG & How does the computer establish miles remaining?

[ff73148]

I have 2022 RT Limited with 1750 miles. Many people have told me it takes a while for the engine to break in and get better gas milage. My question is about the fuel gauge. On the speedo it will show how many miles you have left with the remaining fuel in your tank. How does the computer establish this number? For example I was on a highway ride and the fuel gauge showed a bit over a quarter of the tank with 77 miles left. When I stopped for gas the tank only took 3.5 gallons. Obviously the numbers don't work out. Any ideas?

[YPILOT]

I have 2022 RT Limited with 1750 miles. Many people have told me it takes a while for the engine to break in and get better gas milage. My question is about the fuel gauge. On the speedo it will show how many miles you have left with the remaining fuel in your tank. How does the computer establish this number? For example I was on a highway ride and the fuel gauge showed a bit over a quarter of the tank with 77 miles left. When I stopped for gas the tank only took 3.5 gallons. Obviously the numbers don't work out. Any ideas?

That actually sounds about right. At 77 miles to go you had approximately 2 gallons left.
The computer calculates your fuel consumption as you ride and estimates how far you can travel based on your speed and fuel load as shown on the gage.

[missouriboy]

I go 200 miles per tank, about 50m per quarter, and the gauge shows essentially empty. But it then takes only 5 to 5.5 gallons to refill, indicating I have a gallon or more left when the gauge shows empty. (The 2015 doesn't have computer MPG feature. But the one in my car isn't really accurate either...)

[FrogmanDave]

I estimate the reserve on my 2022 RTL is about 2 gallons. When the bar on the side completely goes away and the remaining miles shows three dash marks (no number) it only takes about 5.5 gallons. And I am averaging around 32 mpg riding mostly in town.

[redrazor]

I estimate the reserve on my 2022 RTL is about 2 gallons. When the bar on the side completely goes away and the remaining miles shows three dash marks (no number) it only takes about 5.5 gallons. And I am averaging around 32 mpg riding mostly in town.

32 mpg is my overall average too. I Couldn't really care less about the mileage. RIDE MORE ..... WORRY LESS!

[blacklightning]

I have the older 2016 F3 models. I get about 38 mpg on my 2016 F3T and my 2016 F3 Limited. Both are better than my buddies 2020 RT. I just picked up a 2021 RT and am anxious to see what it will do.

[ARtraveler]

At best...the on board electronics not to be relied upon fully. There is always human intervention. Here, the person who fills the tank.

To get a good idea for the "ballpark" information from your computer, you must start by filling the tank to the same level each time. I am NOT talking about auto shut off at the gas pump. This method leaves room for about another one to one and a half gallons to be decanted.

To make sure your information is "more reliable" you need to fill to the same level each time.

I start with zeroing on of the odometer registers to zero each time I fill. I use the A register for convenience for me. The B gets used for trips of several fills.

I fill to auto shut off. Pull the nozzel out and carefully decant more gas until it comes up to the ring. I stop, let the tank go down by itself and repeat the fill to the ring one more time. Then I STOP. This process is done each time I fill. For a quick mpg, I take the miles that were on the register and divide by the number of gallons put in the tank. This will give me the mpg per tank. PS. You don't have to be accurate to the 4th decimal place. This is overkill, and the results will not be that much different. I go to 2 decimals, and round that to one. E.G. 4.76 gallons would be 4.8. 4.24 gallons would be 4.2.

This will be the closest you will get. The mpg from the computer is based on averages. This is where not filling the same can come back and bite you. Earlier mention of 200 miles per tank with the 1330 engine are right in the "ballpark." Major deviation from these numbers may indicate something is wrong. If you pull a trailer, drive in mountains, like pushing the wind, or are quick on the throttle, your mileage can vary a lot.

I have owned 7 separate spyders and the system I use has always given the same results. To paraphrase from a movie...I don't need no steenking computer.

Owned four 998's. They gave about me about 170 miles per tank. Light on at about 150 miles. Got 184 miles, one time, but that one was sucking vapor.
Owned three 1330's. All will do 200 miles per tank. Most times, the light does not come on...but it is close.

[Peter Aawen]

I have 2022 RT Limited with 1750 miles. Many people have told me it takes a while for the engine to break in and get better gas milage. My question is about the fuel gauge. On the speedo it will show how many miles you have left with the remaining fuel in your tank. How does the computer establish this number? For example I was on a highway ride and the fuel gauge showed a bit over a quarter of the tank with 77 miles left. When I stopped for gas the tank only took 3.5 gallons. Obviously the numbers don't work out. Any ideas?

I go 200 miles per tank, about 50m per quarter, and the gauge shows essentially empty. But it then takes only 5 to 5.5 gallons to refill, indicating I have a gallon or more left when the gauge shows empty. (The 2015 doesn't have computer MPG feature. But the one in my car isn't really accurate either...)

ff73, the computer does its 'Miles to Empty' (except that's really only 'theoretically' empty, cos it's still purposefully leaving SOME gas in the tank - see next para below ) calculation based upon a range/period of the numbers taken from the 'instananeous' Miles per Gallon calc displayed on the dash, only, because that is in turn working off results that are responding to the throttle settings & revs you have recently been running (albeit admittedly with some delay & 'averaging' built in ) that mpg calc is notoriously 'mildly' incorrect at any given instant; rarely truly achievable; & if you're aware of how it works & want to purposely fool it, you can fairly easily make that display show you something that's really wrong, but looks good - or bad!! So at best, the Miles to Empty displayed on the dash is a vaguely educated Wild Arsed Guess based upon things like your throttle settings, revs, road speed, the volume of gas remaining in the tank (minus the safety allowance) et al in the recent past; and at worst, it's basically just wrong, because any one of the 'readings &/or calculations' producing those figures mentioned has been distorted by something you've recently done or the forces that the Spyder/engine/gas tank contents etc have been subjected to!! So it's a fairly rough GUIDE, not ever intended to be taken literally/verbatim ac litteratim!

Missouri, you need to remember that like most other modern ICEngines, your Spyder's engine is a fairly complex Fuel Injected engine that operates due to components that operate to EXTREMELY fine tolerances which rely on a certain volume of gas remaining in your tank for both Cooling and Lubrication purposes! So if you run that 'gas remaining in the tank' down too low, so that the gas left can no longer adequately cool &/or lubricate those fairly important things like the gas pump & the injectors, CONTINUING TO RUN IT WILL START DAMAGING THINGS!! Now admittedly, that damage might not mean your engine screams to a grinding halt instantaneously, but it will begin and continue to gradually lose power & degrade your fuel economy, and while it may eventually self destruct cataclysmically, is more likely to just slowly run worse & worse over the miles until you can no longer start it or it stops during operation, well short of its expected &/or potential life.... So to avoid that happening within the warranty period, the manufacturers of modern vehicles have ensured that their vehicle's fuel gauges, which can already be fairly unreliable as a true indicator of the gas remaining in the tank cos they already hafta cope with really odd shaped tanks, have been adjusted to display Empty while there's still enough gas left to avoid damaging any of the important & expensive/difficult to replace components that rely on a certain amount of gas remaining in the tank to both cool and lubricate their operation!!
So that's why, when your gas gauge says Empty, it really means:

'Yeah, I know there's some usable gas left, but if you let the gas remaining get anything much lower than this you WILL start damaging things'

And collectively, all that means is pretty much what ARtraveler outlined above - the onboard electronics are not there to be relied upon fully - Sure, you can use them as a guide, and they might even be pretty close some of the time, but you really don't want to hafta bet your life on them!

[ff73148]

Thanks for the feedback.

[vito1943]

After buying my 2021 RT I became aware very quickly with how quirky the data was that show my mpg as well as the fuel gauge itself. I know that I get about 32 mpg generally and use that to estimate when I should stop for a fill up. Rarely do I go more than about 160 miles. And filling up does not mean when the pump clicks off. I guess its the shape of the gas tank, plus the variability in the volume of gas coming out of the pump with the switch depressed. If I have done 96 miles, for example, and know that I used about 3 gallons of gas, it is not unusual for the pump to click off at 2 gallons or so. The only time I really try to fill it to the very top of the tank is when putting it away for the winter. Then I stand at the gas pump squeezing the lever very slightly and holding the tip of the nozzle just above the opening to the gas tank. I then fill it to where I an actually see the gas and that it is almost at the opening. That still leaves room for a couple of ounces of Stabil. But during normal riding I just put in a bit more than when the pump first clicks off, and I pay little attention to the data on the screen other than miles traveled.

[EdMat]

I then fill it to where I an actually see the gas and that it is almost at the opening. That still leaves room for a couple of ounces of Stabil. .

Vito, you might want to add the Stabil before you add the gas so that it mixes well.

[missouriboy]

Missouri, you need to remember...

Remember? Heck, I never did forget! I already knew that stuff, that's why I refill at 200 miles.

I now have over 112,000 miles, and my ICE still runs like new.

[Peteoz]

The onboard distance to empty is great for quick approximations. For better accuracy I have my Garmin XT set up to notify me after 300kms from last fill, and Mrs Garmin then very politely pops her head up at and shows me the nearest gas stations.
It usually prompts me to reset it immediately after a fill, which is a 1 button push. I’m not sure how it knows I have filled up…..I assume it recognises the coordinates as being a gas station, but that is just a pure guess Works a treat for me

Pete