Here's the deal:
-My car's a 97 Avant, so I need a reader to check codes - can't use the neat paperclip method. But I don't have a CEL or anything.
-My gas mileage has fallen from a little under 19 to 15.7 in four tanks, this most recent tank, I did some highway driving, but with a "loaded" car. It's always before the engine can heat up and somewhat hilly.
-It does "surge on startup" which I've heard cited as an O2 sensor indicator.
-I don't drive the car very hard, but I might have mashed it more often than usual this time around.

What do you guys think? Is this def. O2s? If so, pre or post cat? I hear people both recommend genertics and OEM, what are the pros and cons?

Thanks for your aid folks, I'm really counting on you to help me get this sorted out!!

-Jeff

I have a generic code reader, but if you don't have a light on it probably won't tell me much.

On a side note I am in Boston, Canton, Needham area.

The link provided may be your cheapest method of checking codes, &amp; you'll need some sort of diagnostic tool anyway if you plan on keeping your car for long. Your consumption problem could very well be O2s. However, your start up problems may not be O2s; could be ICV or ECT sensor (I'd start with the ECT since it's $6 at ECS tuning &amp; the ICV is ~$200). I don't dare pretend to be an expert on cars; things that go boom are my forte.<ul><li><a href="http://www.obdtool.com/">OBD Tool</a></li></ul>

I'm located down in Central MA near Southbridge. Exit 9 on the ol' pike!

-Jeff

Mine needs a little gas to help start up. My idle starts low &amp; rests at 1200-1400 rpm once warmed up.

But the high rev surge is certainly there to start, which I've heard cited as an O2 sensor thing.

-Jeff