MPG inaccurate data or (something).

[OBO]

Hey Guys, i dont whats going on. i got the 3.8 l rwd recently. Been doing city/highway. If im on the highway cruise control (eco mode) 70-75 mph i get about 23-25 mpg. Short hwy trips less than an hour commute. I thought its rated at 28 mpg highway ? Do i have to go on a two hour or more trip in order to achieve 28-30 mpg ? Also why is that when im in the city even with eco mode on as well as being light on the pedal i still get under 18 mpg. It always shows around 12-14 mpg , why ? Its pretty sunny where i stay, not too much stop and go. If i accelerate the car hard just for a couple secs it goes down to 11mpg or under , Im doing 55 hwy/ 45 city so far and im not cracking 18 mpg or more on the dash. I have already reset It when i got gas. I know the car is heavy but what seems to be the problem? Tire psi 35 all around. Under 40k miles more than 30k miles. What do i need to do ?

 

[Qship]

The rating given to cars regarding the EPA fuel economy is based on "perfect" conditions. No traffic, steady speed, no hills, no inclining or declining roads/highways, probably with no wind resistance, no A/C, no music or other extra accessories that would sap power from the car and require more gas to overcome the drain either. It's the same with battery powered devices, Sure, your smartphone can go 2 days between charges, Ya, if you never turn the screen on, never make a phone call, and never look anything up online.

Everyone will have different mileage. The average fuel consumption gauge in the car is calculated based on how much fuel is in the tank and you going a constant speed with no deviation which is just not possible to actually do for an entire tank of gas.
Cross winds, head winds, altitude (height above sea level), angle of the road, getting a red light, slowing from between 70 and 75 to 50 or 55 and then accelerating back to 70 or 75 etc will ALL change and diminish your fuel economy.

When the EPA tests the cars, it's at 55 or 60 mph for the highway test, and I guess 30-35 mph for the city test. You'll never hit their numbers. It's just not possible.

 

[Mr. Incredible]

MPG is very subjective.

the rated MPG is in PERFECT testing conditions, and at posted highway speeds, faster equal less mpg, you say 75mpg, you are moving faster so your MPG will be lower. Test at 55mph in the same conditions and you will see it go up.

city stop and go traffic kills MPG, ECO mode kills it more, ECO mode is not for city driving, it is for highway cruise control driving, where you are at a consistent speed.

in stop and go traffic ECO is a hinderance because it forces you to press harder on the pedal to get up to speed negating any MPG you might save.


but overall MPG is very subjective, it is all about driving style, tire pressures, road conditions, etc.

 

[RCH04]

As mentioned, fuel economy has never been a strong suit for the current gen G80. The culprit is weight, with the car some 400+ pounds heavier than competitors.

 

[OBO]

The rating given to cars regarding the EPA fuel economy is based on "perfect" conditions. No traffic, steady speed, no hills, no inclining or declining roads/highways, probably with no wind resistance, no A/C, no music or other extra accessories that would sap power from the car and require more gas to overcome the drain either. It's the same with battery powered devices, Sure, your smartphone can go 2 days between charges, Ya, if you never turn the screen on, never make a phone call, and never look anything up online.

Everyone will have different mileage. The average fuel consumption gauge in the car is calculated based on how much fuel is in the tank and you going a constant speed with no deviation which is just not possible to actually do for an entire tank of gas.
Cross winds, head winds, altitude (height above sea level), angle of the road, getting a red light, slowing from between 70 and 75 to 50 or 55 and then accelerating back to 70 or 75 etc will ALL change and diminish your fuel economy.

When the EPA tests the cars, it's at 55 or 60 mph for the highway test, and I guess 30-35 mph for the city test. You'll never hit their numbers. It's just not possible.

ive been seeing ppl on this forum saying they get about 19-21 in the city i dont know how. Ive also heard ppl saying they mostly drive in sport mode still achieve 18+. I know all that varies. From what i heard 70-75 mph is a sweet spot. 55mph is really slow even in the slow lane. Become a menace doing that. I drive conservatively with occasional hard pulls , off the gas coasting type of drive , so i don’t understand.

 

[OBO]

As mentioned, fuel economy has never been a strong suit for the current gen G80. The culprit is weight, with the car some 400+ pounds heavier than competitors.

Its never been a strong suit yes . But if we are talking about AWD then okay. But this is RWD. How is others getting soso mpg driving in sportmode most of the time, 18-19 mpg. What are you getting most of the time ?

 

[OBO]

MPG is very subjective.

the rated MPG is in PERFECT testing conditions, and at posted highway speeds, faster equal less mpg, you say 75mpg, you are moving faster so your MPG will be lower. Test at 55mph in the same conditions and you will see it go up.

city stop and go traffic kills MPG, ECO mode kills it more, ECO mode is not for city driving, it is for highway cruise control driving, where you are at a consistent speed.

in stop and go traffic ECO is a hinderance because it forces you to press harder on the pedal to get up to speed negating any MPG you might save.


but overall MPG is very subjective, it is all about driving style, tire pressures, road conditions, etc.

i just don’t understand how eco mode kills city mpg when its use to lessen the throttle. If i put it in eco mode as well take it gentle on the pedal shouldnt it maximize its potential? You mentioned forces you to press the pedal. But what if you are genuinely actually going gentle on the pedal would it still be a negative ?
It is subjective but for rwd does getting less than 15 mpg on screen sound right to you ? Let alone getting under 10 mpg because i did a hard pull ? Im not even flooring the car from a red light , literally taking it gentle Stoplight to stoplight. What are you averaging most of the time , based on your driving style , conditions etc ?? Which engine ?

 

[Qship]

Its never been a strong suit yes . But if we are talking about AWD then okay. But this is RWD. How is others getting soso mpg driving in sportmode most of the time, 18-19 mpg. What are you getting most of the time ?

I get about 27 mpg averaged out over the course of a week and 99% of my commute is highway driving. 2010 3.8 with 18" wheels. My daily commute is mostly downhill to work, and uphill on the way back. When it's windy, that will have a huge impact on my mileage.
I concern myself more with how many kms/miles I get per tank instead of looking at the average calculation. I get about 435 miles (700 km's) to a tank (when the low fuel light comes on).

 

[OBO]

I get about 27 mpg averaged out over the course of a week and 99% of my commute is highway driving. 2010 3.8 with 18" wheels. My daily commute is mostly downhill to work, and uphill on the way back. When it's windy, that will have a huge impact on my mileage.
I concern myself more with how many kms/miles I get per tank instead of looking at the average calculation. I get about 435 miles (700 km's) to a tank (when the low fuel light comes on).

How do i calculate my miles . So when i fill the car up to full how do i go about it ?

 

[Qship]

How do i calculate my miles . So when i fill the car up to full how do i go about it ?

Just reset one of the trip odometers. When the tank light comes on, look at how many miles are on that trip odometer. I reset it every fill up.

 

[OBO]

Just reset one of the trip odometers. When the tank light comes on, look at how many miles are on that trip odometer. I reset it every fill up.

So forget the mpg calculations, just go by the trip A or B odometers? So lets say you get about 410 miles range to empty when you fill up , your actually gonna go by the trip A odometer to really see the actual miles you driven , as soon as the gas tank light comes on ? That will telll you your actual range miles? That seems like a better route.

 

[Qship]

So forget the mpg calculations, just go by the trip A or B odometers? So lets say you get about 410 miles range to empty when you fill up , your actually gonna go by the trip A odometer to really see the actual miles you driven , as soon as the gas tank light comes on ? That will telll you your actual range miles? That seems like a better route.

I've been doing it that way for years. The problem with the average calculation is there's soooo many variables that will make it change. Injector duty cycle, a slight change of pedal position, a few slow down or stop then speed up situations. It's based on the average for what you're doing at that moment.
For example, if you could get to 75 mph on a flat road, never needing to slow down, with no change in wind speed, wind direction, consistent friction, no turns until you run out the whole tank of gas you'd probably get the fuel mileage you're expecting from the cars calculation.
The moment when wind changes, friction changes, A/C is turned on, there's a curve, a hill, any small variable besides completely flat surface and a 100% constant speed, that average calculation will change, then it will change again as you drive because now the surface is different, the wind has changed, there's no more curves in the road, etc. That's why I just reset the trip odometer. I know that if I can't get 370-420 miles out of a tank, then there's a problem.

 

[OBO]

I've been doing it that way for years. The problem with the average calculation is there's soooo many variables that will make it change. Injector duty cycle, a slight change of pedal position, a few slow down or stop then speed up situations. It's based on the average for what you're doing at that moment.
For example, if you could get to 75 mph on a flat road, never needing to slow down, with no change in wind speed, wind direction, consistent friction, no turns until you run out the whole tank of gas you'd probably get the fuel mileage you're expecting from the cars calculation.
The moment when wind changes, friction changes, A/C is turned on, there's a curve, a hill, any small variable besides completely flat surface and a 100% constant speed, that average calculation will change, then it will change again as you drive because now the surface is different, the wind has changed, there's no more curves in the road, etc. That's why I just reset the trip odometer. I know that if I can't get 370-420 miles out of a tank, then there's a problem.

Im gonna try that method. Thanks. 370-420 miles out a tank, is that based on mostly highway driving or 50-50 city/highway or depending, you just expect to hit anywhere from 370-420 ?

 

[TinsleyC]

Come on, it's not that hard.

- Fill up car, reset Trip A counter.
- Drive.
- Fill up car. Divide miles by gallons put in.

Example: 360 miles / 18 gallons = 20 mpg

 

[OBO]

Come on, it's not that hard.

- Fill up car, reset Trip A counter.
- Drive.
- Fill up car. Divide miles by gallons put in.

Example: 360 miles / 18 gallons = 20 mpg

Divide gallons on the 2nd fill up or 1st fill up ?
Example : 1st fill up - 18 gallons
Gas light on- check trip A counter , divide that miles with first fill up - 18 gallons ?
Or when gas light come on , check trip A counter , whatever that miles is divide that with the new fill up gallons ?

 

[Qship]

Im gonna try that method. Thanks. 370-420 miles out a tank, is that based on mostly highway driving or 50-50 city/highway or depending, you just expect to hit anywhere from 370-420 ?

A mix of both for how I drive and taking city vs hwy as factors as well as environment.

 

[EdP]

It is subjective but for rwd does getting less than 15 mpg on screen sound right to you ? Let alone getting under 10 mpg because i did a hard pull ? Im not even flooring the car from a red light , literally taking it gentle Stoplight to stoplight. What are you averaging most of the time , based on your driving style , conditions etc ?? Which engine ?

So many variables. Short trips in the city is in the 13 to 15 range. Cold even lower. We can't see your traffic so cannot really compare. Big city stop and go? Stop sign on every corner? You have a lot of weight to get moving no matter what mode you are in.

To get the 28-30 you mentioned you have to be going down hill with a tail wind. Most I ever got was 27.3 on a very long haul on cruise control,

I'd suggest getting some of that black electrical tape and cutting a piece about 3/4" square and placing it over the dash reading for mpg. You'll enjoy the car much more.

 

[Mr. Incredible]

i just don’t understand how eco mode kills city mpg when its use to lessen the throttle. If i put it in eco mode as well take it gentle on the pedal shouldnt it maximize its potential? You mentioned forces you to press the pedal. But what if you are genuinely actually going gentle on the pedal would it still be a negative ?
It is subjective but for rwd does getting less than 15 mpg on screen sound right to you ? Let alone getting under 10 mpg because i did a hard pull ? Im not even flooring the car from a red light , literally taking it gentle Stoplight to stoplight. What are you averaging most of the time , based on your driving style , conditions etc ?? Which engine ?

in eco mode taking it easy Then 0-40 takes 15 seconds or longer, if you are getting there faster your foot is to heavy, as a result your mpg will suffer. You are negating any savings. ECO mode is best used for cruising, but if you want to use it for city driving then you have to drive like a little old lady on Sunday, And annoy the hell out of everyone else on the road. Unfortunately the G80 doesn’t show throttle percentage, like some other cars I have had did, but anything above 10% throttle and you kill MPG.

I have a Sport with a 3.3T. Average 19mpg with a mix of highway/city. my commute from house to freeway is 7 miles, highway to work is 12 miles, freeway to office is 4 miles. My average speed is typically 45mph, figured by dividing the distance over the time 23 miles /50 minutes = .46 or 46 miles per hour.

I typically get 320-350 out of a fill up, with the fill being 17-18 gallons, 320/17 = 18.8 mpg.

The car computer says my average over the past 6 months since I reset it is 18.6. And in a typical fill up it tells me I will get 420 miles out of that tank which has NEVER happened with daily commuting, even when I ran the tank completely dry, I topped out at 370 miles 370/19 = 19.4

However I did manage 450 miles out of a tank with a fill up of 18.8 gallons when I drove from CA to TN last summer, which equates 25.2 mpg.

 

[RCH04]

Divide gallons on the 2nd fill up or 1st fill up ?
Example : 1st fill up - 18 gallons
Gas light on- check trip A counter , divide that miles with first fill up - 18 gallons ?
Or when gas light come on , check trip A counter , whatever that miles is divide that with the new fill up gallons ?

There are A LOT of videos on You Tube on calculating gas mileage. Scroll thru them for more good tips

 

[n8800m]

I own a 2019 G80 3.8L AWD. I have checked the car's odometer for accuracy twice using GPS. My car has a 1.87% odometer error. That Is when I drive 100.0 miles per the car's odometer, the actually miles driven is 101.87. I use the car mostly on longer trips and have measured the highway mileage on several trips and it generally has been averaging about 25 to 26 mpg corrected for the odometer error.