Ok I'm going stop you right here when you're about to say, but that's how an MPG Gauge works.

I have owned my car for 11 years and know full well how it is supposed to work and it has been working that way consistently for all of those 11 years. But today though, it is swinging far to one end or the other a lot. Not smooth and gradual like it used to.

Why pray tell is it doing that for?

 

I never use that thing! I do it the old fashioned way. I always fill the tank when I get gas (why make more trips than I have to?). When I print my credit card receipt, I write down the miles stated on my trip odometer and then reset it for the next time. When get home, I do basic arithmetic and divide miles by gallons to get my mpg. I've been averaging about 23 since I've had the car (about 8 years).

 

Did you reset it recently? Mine is always off by 2 MPG

 

So OP is saying the needle is swinging more to the extremes than normal. Possible this means something wrong somewhere, but is it driving the same as normal?

 

Umm the point is I want it to work. Instantaneous MPG to adjust driving my habits. Not the overall MPG.

 

I reset it last night but to no avail.

 

My driving is exactly the same. I swear I do not remember it swinging like it is doing now. Does anyone else's do that? I'd take a video but that's tough to do while driving.

 

Just a guess here. If it is a fidgety needle than it is probably a stepper motor for the gauge. However I believe the reading itself is based on vacuum.

 

The gauge reading is based on a calculation using the actual fuel rate through the injectors. The fidgety needle is probably just a faulty electrical connection.

 

ATTENTION: The objective of my post is to fix it. Not discount its usefulness.