Asked in Nissan Frontier
Why is my 1998 Frontier getting terrible gas mileage in cold weather when it was getting good mileage in warm weather?
I suspect there are several possible causes, but I can only think of three right now. First, it could be a defect in the electronic COMPUTER. Also, the computer makes its fuel mixture decisions based on several pieces of information it receives from SENSORS, and if one or more sensors have become defective, the the computer could be providing an over rich fuel mixture during cold weather. The third possibility is that the THERMOSTAT is diffective, allowing the engine to run very COLD compared to its normal operating temperature. Modern engines are designed to operate at "normal" operating temperatures of 196 degrees F to OVER 212 degrees F [boiling point except for the addition of antifreeze and pressurized cooling systems].j3h All vehicles see a decrease in gas mileage in the winter months, due to the "winter blend" gasoline. If the decrease isn't too dramatic, there might not be anything wrong with the vechicle.