Poor Gas Mileage on a 1998 Ford ZX2
By Richard Rowe
, last updated March 13, 2012
The 1998 Escort ZX2's Zetec 2.0-liter engine was something of a revelation for Ford's staid little economy car. The ZX2 option brought the third-generation Escort from soccer mom to slalom course, and even managed to turn in a respectable 30 mpg on the highway. But time takes its toll on all machines, and fuel economy often is the first victim of progressive component malfunction.
Along with air filters and oil filters, spark plug changes are part of any normal service interval for the ZX2. Ford states you need to swap them out every 100,000 miles, but 80,000 miles is a good real-world figure if you drive the ZX2 the way it was meant to be driven. Old spark plugs, particularly those fouled with carbon and oil, easily reduces fuel economy without causing a misfire severe enough to trigger a check engine light. If you haven't changed the plugs since the Clinton administration, install a set of fine-wire iridium plugs gapped to 0.54 inch.
Sensor failures aren't uncommon with older cars, and a number of dead or slightly malfunctioning sensors can affect fuel economy. Oxygen sensors often slowly and progressively fail, getting clogged with carbon, and the platinum electrodes fail over time. This sends an incorrect message to the computer, causing it to run more fuel-rich than it should. On the intake side of your engine equation lies the mass airflow sensor, which tells the computer how much air is going in. MAF sensor wires get dirty, covered in oil and dust that can cause the sensor to read low and cost you power and fuel economy.
The ZX2 came with Goodyear RS-A high-performance summer tires -- not the most popular choice for buyers of this class of tire. The RS-A is fairly sticky in terms of dry handling, a fact that it owes mainly to its soft tread compound and wide -- almost 9-inch -- measurements. All of this conspires to make a tire that offers huge rolling resistance when it drops to anything below optimum air pressure. The simple solution is to keep your tires properly inflated. The better solution is to buy a set of more modern tires that offer a more ideal combination of traction and low rolling resistance.
Like all cars produced since the mid-1990s, the ZX2 comes with an evaporative emissions system that controls fuel evaporation from the tank. Loose fittings in the Escort's evaporative emissions lines allow fuel vapor to seep out, but you've got a much larger potential leak in a more obvious place. Gas caps are an integral part of your evap system, and are prone to malfunctioning and springing leaks. While this may seem a bit nit-picky, gasoline evaporates surprisingly quickly in warm weather -- enough to make a noticeable difference in your car's fuel economy.