From what I've seen, the light goes on once you have ~2 gallons or less (I don't know the exact number) in the tank. So, for me, at 18 mpg, that would mean I could travel a maximum of 36 miles before the truck started running on fumes.
__________________ 1998 SR5
WAAG Brush Guard
Pics: Here
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Every cloud may have a silver lining, but let's not forget that those silver linings still have their clouds....
I am not sure as to what generation you are talking about. In the 3rd generation I have a 18.5 gallon tank and when the light comes on it is 15.6 gallons empty. After another 40 miles or so, the gauge is below empty and I get about 17.5 gallons in the tank. So I agree, after 36 to 40 miles I am running on fumes, which really is slightly less than 1 gallon left.
So when the light comes on I try to get gas within 20 miles and I rarely push it to 40 miles.
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2001 & 2004 Toyota 4Runner SR5 4X2
Both V6 and both Natural White
"Yeah, I like white and I like 4Runners"
I noticed that my gas light when the Range computer estimated 30miles left. I was able to get back to my house with 4 miles left on the computer. When I got to the gas station the next morning I had 1 mile left. I then filled up my gas tank by 20.078 gallons. Knowing that the 4Runner has a 23gallon tank, I can estimate that there was about 2 more gallons left in the tank and the lines so I can estimate that I had about 30 more miles after the computer had 0 miles on it. Now I wouldn't push it this far again just to find out but it's something nice to know.
haha, yes I can scan the receipt for you if you'd like. I keep my receipts just to keep a running record of my gas mileage. (Insert anal retentive comment here)