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.
i have replaced the oil/air/fuel/trans filters. am using mobil 1 fluids. cleaned throttle body and egr. replaced o2 sensor. no change in mpg :(
replaced tires to pilot sport A/S. upgraded brakes to EBC green stuff and brembo discs(i dont think brakes are dragging- i suppose i would notice during coasting).
put in a can of BG 44k.
there are no driveability problems: idles smoothly (vacuum gauge reads
20 in hg when parked), accelerates well, when crusing at 65 mph (nearly 2000 rpm, flat and level, daytime, no ac) my vacuum gauge reads around 13 in hg. the vacuum gauge needle doesnt vibrate, jump around, or indicate a obstructed exhaust-so engine mechanicals appear to be fine.i dont smell any gasoline so dont think there is a leak, and put in fuel leak dye and no external evidence of a leak.
the temperature gauge reads half way up-so i dont think there is a faulty temp sensor.
any ideas on the problem?
(there are not DTC's, if i hooked up a scanner to read engine sensors-which ones should i look at first?)