Okay, so we all have seen that on the instant FE gauge, there are five little 'bars' between each 20mpg, which means that every one of those little bars is worth 4mpg.

But if you are an analytical nerd like me, you must have wondered, "okay, so what *exactly* does it mean when the bar directly underneath the 40 is lit?" Does it mean I'm getting 40mpg? or 44? or 42?

Well, I have not thought to test this on a really nice flat stretch yet; but the couple of times I have tried to do this, I have reset one of the trip gauges, and then kept going with the fuel economy bar directly under the 40; or one bar to the right, etc. depending on the most favorable conditions.

My very unscientific test, with minimal empirical data, seems to indicate that when up to and including the bar directly under the 40 is lit, I am getting 42mpg. And when it goes one bar to the right of that, I was getting 46mpg.

Anybody else so wacko as me, and tried to capture these values?

 

I've always considered the instant MPG bar as 2MPG (+-) the indicated figure, but never really tested it.

I do know that if the Average is at....say 60, it will hold at 60 as long as the instant indicates the same thing.
I've also noticed in that case if the instant moves either way, even one bar for long enough then the average will follow.

 

I am so glad I am not the only person who is tooling down the highway wondering about these things.

 

I haven't looked at it as closely as coyote, but my impression is that keeping one bar (say the "40" bar) lit will will result in the A or B meter reading 40, rather than 42. But then keeping the 40 bar lit only means you are holding somewhere between 38 and 42, so it's hard to be too precise.

If I were designing a fuel economy meter I would use a speed, in miles per hour, and a fuel flow, in liters per hour, and somehow integrate the ratio. Have to think about this. And I just raised a question in my mind - is the odometer or the speedometer the primary input?

 

The fuel delivery is precisely metered and measured at the injectors (Pulse)
ODO is the other input. I'm not sure of the calculation method though.

 

Just returned from Italy, a "once in a lifetime" vacation. We had an Alfa Romeo diesel for 2 weeks. In the centel console, it has a small readout screen, and one of the values it lists is Kilometers per liter of fuel, much like our HCH FID. It averaged about 16 - 20 KM/L, and had a max of 50 KM/L, which it went to downhill with no foot on the gas. Dang, I found myself playing the mileage game on vacation!!

 

Yes Michael, that's just more evidence that our cars have us completely brainwashed. If we were cartoon characters our eyes would be replaced by those spirally things going round and round.

I can no longer imagine:

- having a car without an instant mileage display
- owning a car that gets less than 40 mpg