Gas mileage calculator - lifetime vs. Trip

[illucid]

So I haven't reset my fuel economy calculator since I bought my truck 8 months ago. I'm at 24,000 km and it says my "lifetime" average is 15.3 L /100km. I'm just wondering if this is actually a representative "lifetime" number. I also reset my trip meter everytime I fill up and the mpg stays close to my lifetime average for the most part. Is this actually a lifetime mileage reading or does it reset after a certain number of miles on it's own??

 

[Conch007]

So I haven't reset my fuel economy calculator since I bought my truck 8 months ago. I'm at 24,000 km and it says my "lifetime" average is 15.3 L /100km. I'm just wondering if this is actually a representative "lifetime" number. I also reset my trip meter everytime I fill up and the mpg stays close to my lifetime average for the most part. Is this actually a lifetime mileage reading or does it reset after a certain number of miles on it's own??

My understanding is that gauge is only good for the last 50 miles not the lifetime if you want to know what your getting top off the tank and reset your trip odometer drive it till empty fill up take the mileage on the trip odometer and divide by the amount of gallons that will tell you what your actually getting it.

 

[illucid]

My understanding is that gauge is only good for the last 50 miles not the lifetime if you want to know what your getting top off the tank and reset your trip odometer drive it till empty fill up take the mileage on the trip odometer and divide by the amount of gallons that will tell you what your actually getting it.

I do use the trip computer exactly that way to find out mpg. But where did you hear that the other computer is only tracking the last 50 miles??

 

[Electrical]

I'd be surprised if it is a 50 mile average. In other vehicles you can choose the interval, and FCA's averaging seems to behave differently than a known 50 mile averaging function.

My opinion is that "lifetime" averaging (by never resetting the indicator) is not representative; it becomes too heavily weighted and misses fluctuations. A better way is to track economy for each tank, and then average those values over the lifetime. ACAR is a great app for tracking fuel and does this automatically.

 

[SpeedyV]

My opinion is that "lifetime" averaging (by never resetting the indicator) is not representative; it becomes too heavily weighted and misses fluctuations. A better way is to track economy for each tank, and then average those values over the lifetime. ACAR is a great app for tracking fuel and does this automatically.

Mathematically, an average is an average, regardless of miles. But if you’re stating that some error is present in the calculator, and that error compounds over time, then that is plausible.

And I agree that the apps are a good way to track long-term economy; many of us are using Fuelie for that purpose, as is evident in our signatures.

 

[Electrical]

Mathematically, an average is an average, regardless of miles. But if you’re stating that some error is present in the calculator, and that error compounds over time, then that is plausible.

And I agree that the apps are a good way to track long-term economy; many of us are using Fuelie for that purpose, as is evident in our signatures.

Uh-oh. I can't believe I'm gonna disagree with the Speedster You're an engineer. You know there are many kinds of averaging functions other than a simple mean. And different ways of implementing like discarding outlying values or using weights.

But even if some sort of simple average is used (x1 + x2 + ... + xN) / N, couldn't that value become so concentrated around a single point that a valid fluctuation has no impact?

 

[SpeedyV]

Uh-oh. I can't believe I'm gonna disagree with the Speedster You're an engineer. You know there are many kinds of averaging functions other than a simple mean. And different ways of implementing like discarding outlying values or using weights.

But even if some sort of simple average is used (x1 + x2 + ... + xN) / N, couldn't that value become so concentrated around a single point that a valid fluctuation has no impact?

Not presuming they are equally weighted (e.g. by miles). But I’m totally open to the error argument, which would support your original point

 

[Conch007]

I do use the trip computer exactly that way to find out mpg. But where did you hear that the other computer is only tracking the last 50 miles??

The dealership when FCA sent me in for a fuel consumption test to verify my ****ty gas milage before the flashes everything from the ecm to the transmission over it