how does everyone know their fuel economy in a older car?

No question is stupid, unless asked insincerely. Yours is mostly ambiguous. I'm not really sure what you are asking. What do you mean by "fuel economy"?

Jerry

_________________
There's a difference between ignorance and stupidity.
Ignorance is not knowing any better.
Stupidity is knowing, yet doing it anyway.

well i have been reading and people are always saying i raised my mielage up from 13 to 19 mpg. how do they know that?

Not to be a wise guy, but it is simple math.

Fill up car with gas and write down the mileage on your odometer.
Drive car until fuel level is getting fairly low.
Fill up car with gas, write down new mileage and take difference from last reading for total miles driven.
Divide total miles by number of gallons on sales receipt.

That's your mileage in MPG (miles per gallon).

Make improvements to car (or what is claimed to be improvements).
Go through process again to determine new calculated mileage.
See if "improvements" made any significant difference.

I'm sure you already knew all of this, but that's the only way I know how to answer your question.

Jerry

_________________
There's a difference between ignorance and stupidity.
Ignorance is not knowing any better.
Stupidity is knowing, yet doing it anyway.

like i said i knew i would get a stupid answer for a stupid question. i just thought there was another way everyone knew that i didnt. thanks for your time,

Of course, there is the old "seat of the pants" method, also. After you drive a car long enough and get accustomed to its quirks, you'll begin to notice a pattern. If you drive it pretty much the same way every week, back and forth to work or school, you'll notice that you always need to fill up on Thursday afternoon on the way home (or something like that). After you make changes that claim to improve your mileage, maybe you now notice that you don't need to fill up until Friday one week, Saturday the next week, and so on. If your driving habits did not change significantly, then maybe something else you did helped your mileage. That's a much less scientific way of looking at things, but it is more of a simple gauge.

Again, I'm not trying to be a wise guy,
Jerry

_________________
There's a difference between ignorance and stupidity.
Ignorance is not knowing any better.
Stupidity is knowing, yet doing it anyway.