1999 Saturn SW1 has 47,000 miles. Has had regular scheduled maintenance as suggested by manufactor. I am starting to notice a decrease in the gas mileage. It's down to about 21 miles per gallon. 80% of driving is done on freeways. My question is: What would cause a car that has regular maintenance begin to show a decrease in the gas mileage?

Thank You
Cherbrig

Several things could cause this.

With no codes, the first place I'd look is at the injector system. Try something like Chevron techron or Amsoil PI cleaner. If you have a clogged injector mileage will go down and a good cleaner will help.

Keep in mind if using Chevron Techron an oil change should soon follow.

1999 Saturn SW1 has 47,000 miles. Has had regular scheduled maintenance as suggested by manufactor. I am starting to notice a decrease in the gas mileage. It's down to about 21 miles per gallon. 80% of driving is done on freeways. My question is: What would cause a car that has regular maintenance begin to show a decrease in the gas mileage?

Thank You
Cherbrig

change your ECTS :) 47k? woww its a babyy!

and yes you have an issue. that SOHC should be well over 30k and with 80percent highway it should be up near 40. try the changing the ECTS and see how things goo

changed my ects and my saturn gets a bit more now.

what are ects

what are ects

Engine Coolant Temperature Sensor