It was saying 40mpg cruised controlled at 50 and 24 MPH

Meaning the computer/car was telling me I was getting 40mph while having the cruise control at 50mph, and as well as having it as 24mph

Is this legit?

Also, tank was a bit above red line, I put $20 in it, and got 160 miles - is this good?

 

You can't calculate mileage with the dollar amount verses mile, you need the gallons.

The DIC gives you an everage. Some read high, some read low. Only way to compare yours is fill to auto shut off and reset of on the trip odometers. Next fillup, calulate the miles driven by the gallons you put in.

But a stead 24mph on a flat level road will give you great mpg's. But you will notice as soon as you hit hills, incounter lights, stop signs, etc. It will change.

 

I find the avg MPG to be very close to reality. I check mine against actual on every fill up.
Getting 40MPG is not unheard of if you are already moving 24 - 50 mph on level ground, possibly with a tail wind?

As Solman98 said, start/stops. hills etc. will greatly effect overall avg though.
On long trips, I have noticed several MPG difference going with vs going against the wind.

If you really want to see how accurate it is:
Fill it up until the autofill pops, reset your avg MPG and trip odemeter and drive until you fill up again.
Note milage (on trip odemeter) and avg. MPG on computer, fill until it pops. Take miles traveled and divide by gallons used this will give you your actual MPG. Compare that with the avg. MPG on the car computer.

Reset the avg. MPG and trip odometer, and repeat.

I think that you will find the avg MPG to be very close.

Note, that you need to set both the trip odometer AND the avg. MPG (computer) each time. Different fuels and/or driving conditions will vary avg MPG.

 

And the instant mpg on the DIC is a waste of time and computer innards.

 

Mine is accurate within .7 mpg. Average speed of 36 mph

 

IF you have the tires that the computer thinks you do, then the DIC is incredibly accurate. You don't even have to fill the tank, it knows the level! I have filled up with 15.875 gallons at exactly the mileage predicted. The average MPG is the one to look at.

IF you have different size tires than what is programmed "Your Mileage May Vary"!

 

Don, you were literally "sucking fumes"!!!

 

Yes, and not even kidding. I had a $1.20/gal. discount waiting at the Giant gas station. I spend more than $1000/month on gas, it adds up!

 

Wow a thousand a month on gas? How many miles do you put on a week and how many miles on your hhr

 

I used to drive 270 miles or more every morning 3amish to 8amsh , the same route for over a year.
I checked with my gps , filled at the same pump .
It seemed to be very acurate.