Poor Fuel Economy - 2006 GP

[Edahall]

2006 Grand Prix
50k miles
Naturally Aspirated


I'm writing on behalf of a friend who is experiencing great pain at the pump due to the cost of fuel and poor fuel economy on his 2006 Grand Prix. Highway fuel economy has gone down from 25 mpg when it was new to 22 mpg. He is religious about keeping the tire pressure at 41 psi so we can eliminate that out of the equation. The car is stock, no Check Engine Light comes up and the engine runs good. What should be look into and/or replaced to restore the better fuel economy?

Also, are there any worthwhile modifications that can be done such as better flowing mufflers or chips to make it less thirsty?

[Tuner-Extraordinaire]

Supercharged or Not?

[Fivefingerdeathpunch]

41 is a little high, I would say 35psi alot better.

Driving the speed limit is also key, these cars like 65-70mph for fuel economy.

Do a tune up, new air filter, New Stock replacment plugs, Clean the throttle body to get rid of carbon build up. Make sure he is running the proper grade of gas for the car. 87 for NA motor and 91+ for Supercharged motors.

[SlowNA06]

Of course, we'd recommend loweing back down to 35psi for safety's sake.

Maintenance at 50,000 miles:

• Transmission flush + filter + trans reset
• Coolant flush
• Clean mass airflow sensor
• Clean throttlebody
• New intake air filter

Modifications to increase fuel economy:

• 9" cone intake filter sans box
• Headers
• Custom tune
• Lighter tires
• Lighter rims
• Upgrade electrical grounds (Big 3)
• Remove excess junk from inside car

[Compg4me]

How do you do a trans reset?

[Tuner-Extraordinaire]

unplug battery.

[Edahall]

Of course, we'd recommend loweing back down to 35psi for safety's sake.

Maintenance at 50,000 miles:

• Transmission flush + filter + trans reset
• Coolant flush
• Clean mass airflow sensor
• Clean throttlebody
• New intake air filter

Modifications to increase fuel economy:

• 9" cone intake filter sans box
• Headers
• Custom tune
• Lighter tires
• Lighter rims
• Upgrade electrical grounds (Big 3)
• Remove excess junk from inside car

What's "Upgrade electrical grounds (Big 3) all about?

Any comments on which custom tune is best for fuel economy and what kind of increase are we talking about?

How about O2 sensors?

[SlowNA06]

How do you do a trans reset?

You can either leave the battery unplugged for a while - I think it's 20 minutes. This, of course, is done after the flush.
Or, you can use a TechII to reset it.

What's "Upgrade electrical grounds (Big 3) all about?

You rewire your grounds with thicker wire.

Any comments on which custom tune is best for fuel economy and what kind of increase are we talking about?

A custom tune means that a nice man sits in your car and tunes it for you with his laptop. That's the only kind there is.

How about O2 sensors?

The O2 sensors are fine. Don't touch 'em.

[Edahall]

Thanks for all the replies.

Here's another thing. Due to allergy issues, my friend leaves his climate control on "recirculate" at all times. I believe this is causing the A/C compressor to run at all times and possibly reduce fuel economy 10-15%. Is there a way to keep the climate control from letting outside air in and at the same time, not turn on the A/C compressor?