My 2002 has 107K miles, SES light came on. Dealership said it needs new oxygen sensors. Got them replaced, dealership "reprogrammed" the engine control module, and now mileage on highway has dropped from 35mpg to 28-29mpg. Nothing else changed.

Any ideas what the problem or the fix is, before I go back to the dealership?

 

The EPA says that a 2002 max should get 28 mpg highway and they're pretty liberal.

It could be that your o2 problem could have run your engine too lean?

 

wow 35mpg...I couldn't go 55 downhill in neutral and get close to that.

 

are you getting 35mpg according to your digital readout on your trip gauges or are you actually figuring it up exact. my trip gauge always gives me mpg numbers that i know im not getting.

 

Once I drove from CT to VA. My trip guage said I was getting 47 mpg and averaging 27.5 mph .

In reality, it was about 25 mpg, and I was averaging about 80 mph. I don't really know how that guage is supposed to work, all I know is that it doesn't.

 

both. I do a lot of highway driving, so i used the digital readout and the fill-it-up-and-check-the-trip-odometer method.

 

I must say 35MPG is great but pretty hard to believe.

I know of no V6 giving 35MPG on highways!!!

 

I would say the drop to 28MPG is nothing to complain about (although from 35MPG I would). I'm not exactly sure if the "reprogramming" of the o2 sensor was neccessary, though. I believe it's just a plug and drive off situation for o2's.

 

I'm going to agree here.



OP: Did you reset the ECU, or at least disconnect the battery for a bit?

 

uhh.. most i ever got all highway was 25.. and the only time i slowed down was when i reached an exit for the airport
so i call BS on ur 35mpg!
-=)

 

2002 maximas dont get 35 mpg on the highway. I have an 03 and its also a manual and no matter what speed i get I still avg between 24 to 27 mpg roughly. Its reset with each new fill. If you fill it with regular you'll get more...unfortunately I pay top $$$ for fuel so my car hasnt seen regular before.

 

Get more what, MPG? I don't think so.

 

35mpg on the highway is insane. It doesnt matter how I drive because I just about always get 15mpg in city driving and 20mpg at best on the highway.