cooldog

I've got a 2008 vert. I bought it at 44K miles, and it came with a Vararam CAI installed. I'm a fairly gentle driver, and the highway and average fuel consumption seems high to me. It averages about 20mpg, and got only 23.9 on a 800 mile highway trip.

In my '05 coupe, I used to get 25mpg average, and between 29 and 31mpg highway, depending on speed.

I've added headers, DeWitt rad, 160 degree thermostat, and a dyno-tune since I bought it. None of these has made the slightest change in the fuel efficiency (as pretty much expected).

I've been advised that my first step should be to replace the front O2 sensors.

So, here are some questions:

What brand is recommended?

Also, I've seen an adapter for running the rear sensors in the front. It's said that they have stronger heaters, which helps compensate for the greater distance from the exhaust ports due to the long-tube headers. Any thoughts on this???

Thanks.

Loaded08

Sorry, I'm not addressing your question although I would stick to stock OEM parts when it comes to O2 sensors.

If your concern is gas mileage, consider a few things, your '08 is heavier (vert) and has a bigger engine (6.0 vs 6.2). Also, are you driving an auto now where you had a 6 speed before?

Also in terms of mileage, have you considered changing brands of gasoline? I know I get much better mileage running Chevron, 76, Shell, etc. than I do running grocery store brand, Arco, Tesoro, etc.

Edit: Running Cooler is far worse for fuel economy (radiator, 160 thermostat).

Cheers,

cooldog

It's still an M6, and I expected to lose about 1mpg, not 5mpg. Does not seem sensitive to brand of fuel, and mpg is unchanged before and after the thermostat change.

hebdog7

Plus the only thing the rear O2's are there for is to make sure that the cats are working properly.

cooldog

These are all four-wire sensors, and I believe that they are heated.

Yes, I know the rear O2 sensors are not involved in setting AFR, and they've been "removed" by the tune.

But that's not at all what I'm asking.

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EDIT: Not sure this fits anyway - it's flat to square, instead of trapezoidal!
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Here's the "Rear to Front O2 Sensor Adapter"

"These adapters allow rear oxygen sensors to be used in place of the front oxygen sensors on certain GM vehicles. The rear oxygen sensors have stronger heaters in them which keep the computer in closed loop. Typical applications are in vehicles which have aftermarket exhaust manifolds (headers). "

http://www.racetronix.biz/itemdesc.a...LS1-O2&eq=&Tp=

So, question one: does it make sense to do this? Question two, is there a better brand of sensor?

hebdog7

I have not heard of this before, but I would not personally do it being that these cars are designed to have open and closed looped maps ran.

I run the Bosch O2 sensors. I don't really think there is a best sensor to run just what your personal preference is.

I would put the stock thermostat back in. Unless you are running the drag strip 80% of the time you are not really gaining anything IMO. These motors are designed, for the best emissions, to run at an optimum engine temp range of 210-220 degrees. Not the best for performance though.

Here in Texas I get WAY better mileage in the summer time rather than now which is at best 23ish highway.

I would also have the tune rechecked and pull the O2's and see if they are getting fouled up.