It sounds like you guys need to fill up the tank higher, and additionally, realize that the "reserve" is a whole 1.0 gallons of your 2.8 gallon tank. If you are not filling it up enough, you are running on less than 1.8 gallons for your "full" tank. You can leave the valve on reserve all the time, and have the full 2.8 gallons available to you, but you won't get any warning before it is empty. You will just have to watch the trip meter.