While ethanol and flex-fuel vehicles are rapidly gaining in popularity, auto companies, including General Motors Corp., are experimenting in-house with some unusual ways of helping drivers to save at the pump, The Detroit News reports. One of the systems being developed is "brake to neutral," which would automatically shift your vehicle from drive to neutral when you step on the brake in certain situations, such as at a red light. The theory is that even this simple action helps to dial down the engine enough to result in fuel savings of 3 percent to 4 percent. The system is promising, because it offers fuel savings without the expense of complicated hybrid systems, according to The Detroit News. The one problem that companies have yet to work out with "brake to neutral" is how to handle braking on a hill without the car rolling backward. Automakers are also looking at ways of putting gasoline under higher engine compression, similar to how diesel fuel is treated, which can also result in fuel savings. But with this experimental system, there are "knock" issues, which would be unacceptable to U.S. consumers who do not tolerate the engine noise.