Fist Time I did a MPG Check On The Highway..

[95AVALON_GUY]

i have a '95 Avalon with 221K on it.. And for the city i get 350 to a tank and that equates to 23 mpg...

Yesterday was the first time i did a highway trip.. Here is how it went.

I filled up at a gas station that is less than .2 from the highway i was using. So filled up completely, got on the highway and proceded to go to my destination which was 85.6 miles away. I was crusing on the hwy at 70 using cruise control. When i got to my gas station, i filled up......

I put in 2.069 gallons of fuel. And like i said i got 85.6 miles. So 85.6 / 2.069 = 41.3 MPG

that was amazing that i only used 2 gal. of fuel and went 85 miles

Very happy. Should make for a good trip when i go to Michigan in July

[worthywads]

That's possibly realistic, but keep in mind that small a fill can be off by quite a bit from pump to pump. Keep tracking your mileage by tank. If you are really interested a scangauge is great for accurate mpg and will really help you see what helps and hurts.

No affiliation with scangauge, just a fan.


www.scangauge.com

[95AVALON_GUY]

Originally Posted by worthywads

That's possibly realistic, but keep in mind that small a fill can be off by quite a bit from pump to pump. Keep tracking your mileage by tank. If you are really interested a scangauge is great for accurate mpg and will really help you see what helps and hurts.

No affiliation with scangauge, just a fan.


www.scangauge.com

I was using my Garmin GPS unit to calculate my my miles. Then like i said i filled up... Took the number of gallons to fill up and divided it by how many miles it took...

I do not see how my data could be wrong from pump to pump......

[TrailDust]

Originally Posted by 95AVALON_GUY

I do not see how my data could be wrong from pump to pump......

Filling up to the lip of the fuel spout is about as precise as you can get, so if you happen to be counting on when the fuel pump clicks off as your point of reference the numbers could be off significantly. How are you filling up?

[worthywads]

^

Not wrong but maybe not very accurate to the actual gallons used if from 2 different pumps.

Your 2.069 gallons is only accurate if the second fill brought the tank back up to exactly where it was when you started. Being short or long by .25 gallons on a 2 gallon fill is reasonable, but that's 12.5% error. On the other hand .25 gallons on an 18 gallon fill is 1.4%. A half gallon difference is not uncommon.

Topping all the way off to the top of the filler neck would make the different pumps irrelevant as TrailDust said.

[95AVALON_GUY]

Originally Posted by TrailDust

Filling up to the lip of the fuel spout is about as precise as you can get, so if you happen to be counting on when the fuel pump clicks off as your point of reference the numbers could be off significantly. How are you filling up?

When the nozzle clicks, i ALWAYS fill up to next whole dollar....

For instance, when i originally filled up after i drove the 85.6 miles, when i got gas the total was $5.55 for 1.914 gallons of fuel. But i went all the up to $6.00 even for 2.069 gallons of fuel.....

Does that help?

[TrailDust]

Originally Posted by 95AVALON_GUY

When the nozzle clicks, i ALWAYS fill up to next whole dollar....

For instance, when i originally filled up after i drove the 85.6 miles, when i got gas the total was $5.55 for 1.914 gallons of fuel. But i went all the up to $6.00 even for 2.069 gallons of fuel.....

Does that help?

I think that matters big time when your running the numbers later on, especially if the mileage/fuel used is a small amount. Unless you can visually verify the fuel level as it comes to the lip of the spout, you just don't know where the level is at if you continue filling after the click...too much ambiguity when there's little fuel or mileage involved, if you see what I mean?

[worthywads]

I'll add that with you fillup method and using gas at $2.50 you could see a difference of 0.4 gallons just with your rounding up method, between 2 tanks. Not much on a full tank, but a lot on a 2 gallon fill.

[htwo]

If you round it up to the next $0.25, you'll get a more accurate reading.

[kevintomb]

Yeah not accurate at all. You need to do an entire tank of gas, as any small portion will automatically be off a GOOD amount. Imange it this way,. say you went uh....12 miles and you refilled and it took uh say a half gallon to fill up, depending on WHEN the pump shuts off you could also be at say .3 gallon or all the way up to .7 gallon depending on not only how you filled the tank last time, but just pure luck of when the pump shuts off. It doesnt shut off automatically at the same point EVER. Its a random point that depends on how your car is sitting, how level it is, how much is in the tank to begin with and some other factors.
The point is, using a tiny amount of gas to figure mileage isnt very accurate