Can'T Approximate Without The Right Data

"approximate the data for yourself" person: sure, if you know the following:

1. Exactly what your tank capacity is. I think mine's somewhere around 11 or 12 gallons, but if you're talking about how far you can go before running out, there's a huge difference between 11.2 gallons and 11.5 gallons. And when I say "huge difference" I mean 6 or 7 miles, which is pretty significant if it's, say, how far you have to walk to get gas. (And before you say it, I've been through my owner's manual and have not found this info.)

2. Exactly how low your tank can go and still feed properly, or what we might call the "usable capacity" of the tank. Knowing your tank holds precisely 11.5 gallons will mislead you badly if it turns out that the last half gallon isn't really usable because of the way the gas feeds from the tank to the engine.

If I really wanted to know, I might run the car dry once to find out, and then use your method to keep track in case anything changed, but I wouldn't use it to get the initial number.

Anyway, my '94 Saturn SL2 doesn't even have a light as far as I know, just a gauge. When it was new, it would go a little ways after the needle hit E. I never tested how far. In its later years, I have run out a couple of times and it was actually before the needle had properly landed on E.

(Such occasions would, of course, have been a perfect time to find out my actual usable tank capacity, except that when someone else, who you've called out to help you, is waiting around while you fill your gas can, you forget details like recording exactly how much you put in the can...)

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