You never want to run out of gas midway through grilling. To that end, we tested three propane level indicators, which are designed to show how much fuel you have in your tank. One sounds an alarm when you've got two hours of cooking time left. Unfortunately, it works only when the grill is ignited. Another model we tested works like a mood ring, with sporadically illuminating color bars that we found nearly indecipherable. We much preferred the final entry, which looks like a car gas gauge. You hook the indicator to the collar of the tank; when you lift the tank three inches off the ground, it registers the gas level by weight.