On the original factory's sending unit in my DeLorean, the light would come on when there is two to three gallons left which is about the same with the Tankzilla units. With the Tankzilla units (I had two units, for one was a replacement) both of them turned the warning light on when there is slightly around three gallons left. The warning light will start to FLICKER on and off when you have 3 to 4 gallons in the tank. When the lights STAYS ON, you have 2.5 gallons left as reserve. Many times when the light would come on and a stays on, I would continue to drive and put on at least 25 to 35 miles on the odometer (at times up to 38 to 40 miles and I won't push it beyond that) before I would stop to fill up at the next gas station. I would fill my tank until the gas is up to the opening of the neck. (Yes, I know I am not supposed to do that, but I am driving on a long trip so the gas will get consumed within several minutes to bring the level below the fill neck and my tank to the filler neck don't leak.) I would then drive on, until the lights come on again and I would fill it up again in the same manner. In doing so, I can get a very accurate amount of gallons filled, which is 11 to 12 gallons. The DeLorean's tank capacity is rated at 13.2 gallons, and subtracting the 11 or 12 gallons filled (as indicated by the pump -- and there is variations which leads me to believe the pumps are NOT all accurate... hummm???), therefore, there is 2 gallons in reserve. Remember, this is my car and "its" sending unit ... yours may differ slightly. FYI... The brand of gas, the octane, the highway's terrain and weather conditions and traveling at an average speed of 60 MPH, I would get 27 up to 30 MPG with a passenger (my wife of 130 lbs) with additional luggage and other gears of 25 to 70 lbs in weight as payload. This for me, makes the DeLorean worth its weight over many other exotics cars I driven or owned. Kayo Ong #5508 Lic. 9D NY [Non-text portions of this message have been removed]