poor gas mileage-99 alero v6

||hello- ||i have a 99 olds alero v6, 60k miles. when new it got 26 mpg combined ||suburban-highway and 32 mpg highway. however, during the last year, ||the fuel economy has gone down to 21 combined and 26 highway. || ||the temperature gauge reads half way up-so i dont think there is a ||faulty temp sensor.

There are more than one temp sensors. One works the gauge, another tells the ECM when it's warmed up, and there are doubtless others. If you just want to change a sensor and try it, the temp sensor for the ECM directly affects fuel mixture, so it's a prime suspect. It should cost around $20. Texas Parts Guy

On this and most other recent applications, there is only one coolant temperature sensor. The PCM sends the coolant temp over the data bus to the IPC which controls the coolant temperature gauge and/or coolant temperature warning indicator. If the temperature gauge seems to read the same as it always has, then the coolant temp sensor is most likely fine.

Roger

I would get rid of the Alero, they are junk and built like junk, their not dependable like other GM cars

I also have a '99 Alero V6, just turned up 80,000 miles. My mileage figures were just like yours, about 27 overall, up until about 10,000 miles ago, maybe 7 or 8 months ago, when they dropped to where I am getting more like

Lee Richardson

Dependable like other GM cars? You're kidding, right??

Have the codes read. You could have a bad knock sensor which will retard the timing and not light the CEL.

Ok Some other GM cars were actually reliable. Maybe older stuff.