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internal88, Auto Mechanic
Category: Car
Satisfied Customers: 2590
Experience:  I've been working with automotive industry for almost 20 years. I also have an engineering background. Saving one car at a time.
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my 2008..headlight..harness..mpg..11.8 and I have filled my tank

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I had my 2008 Outlook worked on to put on a new headlight electrica harness. My mileage has now gone down from about 14 mpg to 11.8 and I have filled my tank up three times with the same 11.8 mileage. What can I do ????

internal88 : I'm going to help you out.
internal88 : The headlight harness has nothing to do with mpg
internal88 : When is the last time the spark plugs were changed?
internal88 : Air filter replacement, check the tires for 32 psi.
Customer: replied 5 years ago.
This is a very basic answer and I am not pleased with it and would not accept this basic response as an answer from an expert.
In order for me to diagnose your vehicle, I will need you to communicate with me. There are many factors that your mpg is low.

There is no adjustment for the fuel consumption. There is no manual setting for the fuel. The fuel compsutation is controlled by various sensors. Such as your throttle position sensor, air charge temp sensor, oxygen sensors, map sensor and most importantly ecu. All of these senors create a fuel map and air fuel ratio.

Your driving habit is a big factor as well. If you full throttle 70% of the time your Mpg will be lowest.

My question is there any check engine light on? Because if one of these senors are out of oe specification range it will trigger the check engine light.

The fuel addictive might help but not a Guarantee.
If all the basics equipments is check out and they are all ok. Also If you're driving conservatively and all equipments are ok. Then you have a clogged or dirty fuel injector.
Please ACCEPT my Answer if I have helped you. This is how I get credit for my time researching your question. A BONUS is greatly appreciated! I will still help you after the acceptance.
Customer: replied 5 years ago.

What can you tell me about fuel performance chips which claim to interface with the ECU (Engine Control Unit). This is the main unit that the Performance Chip interfaces with to create more power, fuel mileage, etc.


  • The ideal air fuel ratio (mixture) is termed stoichiometric. This means that there are 14.7 parts air to 1 part gasoline. By achieving this air fuel ratio an engine is able to run more efficiently, meaning better gas mileage, better emissions and more horsepower. Through rigorous research we were able develop a system that adjusts the factory ECU's settings in order to produce this ideal fuel mixture.
  • Ideal ignition (spark) timing can only be utilized once ideal fuel ratio has been achieved. By advancing the spark timing the piston is allowed to have a longer power stroke, and achieve a more complete burn of the gasoline vapors inside the combustion chamber. These factors are essential in creating more efficient power for a smaller amount of gasoline.
  • This system allows you to run more advanced spark timing with an ideal fuel ratio. Being that our system runs more advanced spark timing and a stoichiometric fuel mixture we advise that you can continue to use the same fuel that was initially recommended for your vehicle. Our claims are based on this, so there is no need to run higher octane fuel.
  • I see that you have one question and the other three points are basic facts.

    To answer your first question - the simple answer is no, those performance chip you see in the magazines are falsely advertised.

    I think you have the GM engine in your 2008 VUE.
    The software engineers in GM that create the OE fuel map and A/F ratio already did their research and have optimized for maximum power along with MPG. Any modification to the fuel map setting will not be recommended.

    In summary you cannot add or modified a chip to make increase mpg and HP. Current ECUs are flasheable. Meaning a qualified tech can flash your car while on the dyno to adjust the fuel injector pulse for more HP and can eliminated the redline. (This is for serious tuner only and lot of time plus money will go into it!)

    Why would you want to bump up performance anyway? I think MPG is your biggest concern, right.
    internal88 and 4 other Car Specialists are ready to help you
    I'd suggest you to get a drop in k&n air filter. The K&N's replacement air filters are designed to increase horsepower and acceleration while providing excellent filtration. The High Air flow can help the engine breath better therefore increase the mpg.. They are reusable and also Has a million miles warranty. Part number for you car is 33-2404. It's only $50.
    Customer: replied 5 years ago.
    I will try this air filter. So for a 2008 Saturn Outlook the part number is 33-2404 for this air filter? Thanks
    Yes that is correct .