You should
not use 30W engine oil in a 1999 Ford Contour. 30W is a monograde oil, meaning its viscosity doesn't change much with temperature. Modern engines, including the ones in 1999 Ford Contours, require multi-grade oils (like 5W-30, 10W-30, etc.) that provide better protection across a wider range of operating temperatures. Using a monograde oil like 30W will likely result in poor engine performance and increased wear, especially in cold weather.
Always consult your owner's manual for the recommended oil viscosity and specifications. The manual will tell you the correct weight and type of oil for your specific engine.
