Tips for maximizing fuel economy

Discussion in 'General Tahoe/Yukon/Escalade Discussion Forum' started by JKmotorsports, Nov 5, 2007.

  1. JKmotorsports

    JKmotorsports tahoeyukonforum.com

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    Maximizing Fuel Economy/Minimizing Costs

    I know we are all concerned about mileage with these big heavy SUVs we choose to drive, so here are some gas saving tips.

    The best fuel economy possible is the direct result of proper maintenance and good driving habits. Listed below are GM's recommendations to achieve the best mileage possible. The first group are things to consider for your vehicle, while the second are tips relating to your driving habits.

    Vehicle Considerations:

    Tire Pressure - One of the major contributors to poor fuel economy are under inflated tires. Tires low on pressure create drag that the vehicle's powertrain must overcome, wasting dollars in fuel. Always keep your tires inflated to the proper pressure as shown on the vehicle placard. This not only serves to increase gas mileage but cuts down on tire wear, further decreasing your costs per mile.

    Air Filter - A vehicle that has a dirty air filter can't efficiently draw air into the engine. This restriction forces the engine to expend energy to "breathe" wasting fuel in the process. Change recommendations are found in your vehicle Owner's Manual.

    Proper Viscosity "Starburst" Rated Oil - Always use the proper viscosity oil in your engine. Oil that has a higher than required viscosity will create more drag on the internal components of the engine, causing more work for it, especially when cold. Each Owner's Manual contains information on the proper type of oil for your vehicle. Look for the "starburst" symbol on the front of the bottle, and the SM rating on the API circle on the back label. If you are in doubt, stop by your dealer for an oil change, and any other services required. Most current GM vehicles are equipped with oil life monitors to further assist on the "when" to change your oil. (Aveo/Wave/Optra/Epica currently do not have oil life monitors).

    Note: GM Vehicles DO NOT require additional engine oil additives. Some additives may cause harmful effects to the internal seals and additionally void the terms of your vehicles New Car Warranty.

    Top Tier Fuels - Some fuel manufacturers provide gasoline advertised as TOP TIER DETERGENT GASOLINE (Chevron, Conoco, Phillips 66, Shell, Entec Stations, MFA, 76, Somerset Oil, QuikTrip, and Kwik Trip in the U.S. and Chevron in Canada. These fuels are preferable when and where available. They help to keep your fuel injectors and intake valves free of deposits. Clean engines provide optimal fuel economy, performance and reduced emissions. When Top Tier fuels are not available, consider a bottle of GM Fuel System treatment PLUS, P/N# 88861011 (in Canada, # 88861012), at oil change time which will remove intake system and injector deposits. GM does not recommend any other fuel system cleaner.

    Important: DO NOT confuse Top Tier Fuels with Higher Octane (Plus/Premium Grade Fuel) commonly sold at most all gas stations. Plus and Premium fuels are required in some high performance GM vehicles. However, they do not necessarily represent higher detergency present in TOP TIER Detergent Gasoline.

    Note: E85 FUELS: Only vehicles designated for use with E85 should use E85 blended fuel. E85 compatibility is designated for vehicles that are certified to run on up to 85% ethanol and 15% gasoline. All other gasoline engines are designed to run on fuel that contains no more than 10% ethanol. Use of fuel containing greater than 10% ethanol in non-E85 designated vehicles can cause driveability issues, service engine soon indicators as well as increased fuel system corrosion.

    Use the Recommended Grade (Octane) Fuel-
    Purchasing higher than required octane fuel is a waste of money. Using higher octane fuels in a vehicle that only required regular unleaded fuel will neither increase performance nor improve gas mileage. In all cases refer to your owners manual and ONLY use the octane rated fuel recommended for your vehicle.

    Important: In high performance GM vehicles that DO require Premium (91 octane or higher) fuel, you MUST use fuels of at least this octane. Use of lower octane fuel may result in reduced performance, knocking, and/or permanent engine damage not covered under the terms of the New Vehicle Warranty.

    Check Engine/Service Engine Soon Light - Is the Check Engine/SES light on? When this light is on, the vehicles On-Board diagnostics computer has noticed that something is wrong. GM vehicles have many sensors that the computer uses to both control and sense actual fuel usage. When the computer lights the Check Engine/SES light it has lost some ability to run efficiently. This may result in increased fuel consumption, increased emissions, and/or driveability concerns.

    Spark Plugs - Even though current GM vehicles have 160,000km (100,000 mi) service intervals for spark plugs if your vehicle is at that point in it's life, have the spark plugs changed to assure proper running and continued efficient, trouble free operation.


    Changes In Driving Habits:

    Slow Down, Drive Smoothly - Avoid quick/full throttle acceleration from a standstill in town and high cruising speeds on the interstates. While the optimum MPG for highway cruising speed varies from vehicle to vehicle, faster is almost always worse. If your vehicle is equipped with a Driver Information Center that displays Instant Fuel Economy, select that read out and vary your cruising speed while on the highway. The display will change continuously with uphill and downhill sections but you should quickly be able to identify on level ground the speed range that your vehicle does the best in.

    Empty Your Trunk - Avoid leaving unnecessary items in your trunk. It takes power to move increased weight and that means more gasoline consumption and reduced performance. While the change may be slight, multiplied by thousands of miles, it all adds up.

    Avoid Extended Idling - There is no need to idle your engine till it reaches operating temperature. Idling wastes fuel.

    Combine Trips - Your vehicle uses much more fuel when the engine is cold. This is especially true in the winter months when the engine will take the longest to warm up. Combine errands or trips so that the vehicle only needs to warm up once to encompass many different stops.
     
  2. 73shark

    73shark Full Access Member

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    Saw an interesting driving tip for city driving. Try to never have to apply your brakes over 40 mph.
     
  3. High4

    High4 Full Access Member

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    A change to all synthetic (oil, transmission, transfer, diffs) will give immediate positive results in mileage. I know it is initially expensive but if you plan on keeping your truck for a lot of miles/years it is worth the expense just for the extended life of the drivetrain and the increased mpg is an added bonus.
     
  4. frankthetank

    frankthetank New Member

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    I would have to disagree with you on using the recommend fuel octane, Higher octane does increase fuel economy, its a not a myth. In my yukon I noticed a 1.2 average mpg drop when using 85 compared to 91. Thats with the same driving habits. Higher octane has a slight impact on horsepower thus improving miles per gallon. Why would someone use 115 octane in racing if it did not have an impact on their performance of their vehicle. Just my 2 cents.
     
  5. frankthetank

    frankthetank New Member

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    I forgot to add "HOOK'EM HORNS"
     
  6. LAP TOP GAMER

    LAP TOP GAMER Full Access Member

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    If I just keep my foot out of it I can save gas and gas getting to $4 a gallon soon and we might even see $5 a gallon, I'm starting to be more conservative in my driving.
     
  7. JKmotorsports

    JKmotorsports tahoeyukonforum.com

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    I agree with you on the higher octane issue increasing mpg. But for some reason, GM engineers say otherwise. I know higher octane helps provide more power because it combusts easier. In most cases, this would in turn provide better mpg figures. I almost didn't list that as a tip, but since it came from GM engineers, I went ahead and posted it anyway.
     
  8. Getwired

    Getwired Full Access Member

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    Uhm...

    Um, maybe I remember chemistry incorrectly, but doesn't the higher octane rated gasoline autoignite/detonate slower, thereby creating a more steadily/slower burning fuel, increasing fuel economy? The lower the octane rating, the faster the gas burns. In a diesel engine, faster burning fuels is desirable (cetane rating), but in electric-spark ignition engines, slower is better for performance (compression is better) and fuel economy.

    Reference: http://en.wikipedia.org/wiki/Octane_rating and over here: http://auto.howstuffworks.com/question90.htm

    Check it out! Interesting stuff.
     
    Last edited: Nov 8, 2007
  9. LAP TOP GAMER

    LAP TOP GAMER Full Access Member

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    Yeah but is the efficiency gain enough to offset the cost of a premium fuel?:skep:
     
  10. Getwired

    Getwired Full Access Member

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    Believe it or not, yes! (But barely...)

    Funny -- my wife was just in here shoulder surfing while I was responding...she asked the exact same question! For me, the answer is yes, but barely. I appreciate the better performance, and the smoother operation of the engine. I ran 87 initially, and the performance was fine, but the engine knocked here and there, and fuel economy sucked. I run a discount grade 93-octane fuel most of the time (Costco), and run a tier-one (Shell V-Power) tank of fuel through every 5th tank or so. I'm on my V-Power tank now, and she purrs!!! :D Plus, I HAVE to run 91+ for my Edge Evolution to not hose anything up; and since I can't get 91 in my region, I use 93.
     
    Last edited: Nov 8, 2007
  11. Rafael

    Rafael Full Access Member

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    You win the prize.:clapping: You'd have to get about 10 to 15% better mileage to warrant the extra cost of high octane fuel.

    I've found the best way to get good mileage is to only drive downhill.:D
     
  12. Getwired

    Getwired Full Access Member

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    Numbers for ya

    Here's my math, which was based on numbers before my Volant intake or Edge Evolution:

    1) 87 is $2.95, avg. fuel economy is 9.9 MPG
    2) 93 is $3.25, avg. fuel economy is 11.1 MPG
    3) 2.95 / 9.9 = 29.73 cents / mile
    4) 3.25 / 11.1 = 29.28 cents / mile
    5) Cost difference is negligible (in my favor), performance is better, and it's better for my engine.

    It'd be interesting to put the PCM back to stock, and try this again to see if there really is still any difference, but since I'm not a paid researcher, I'll just keep things running they way they are and shoot for 13.5-14 MPG in mixed driving.

    Bottom line for me: better performance for a hair less overall cost. What's not to like? Do the math for yourself - you might be surprised.
     
  13. frankthetank

    frankthetank New Member

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    That's kind of my reasoning too. I live in Denver right now going to school. Driving up I-70 in to the ski country is really were I found the difference in performance.
     
  14. JKmotorsports

    JKmotorsports tahoeyukonforum.com

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    Sorry. I read over what I wrote and I did word it wrong. Higher octane fuel helps provide more power to higher compression engines than it would comparatively in lower compression engines because it combusts slower. Thx for pointing that out to me.
     
  15. JRTV8

    JRTV8 Full Access Member

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    Just be light on the accelerator :D
     
  16. HofB99

    HofB99 Full Access Member

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    Ummm...REALLY hard to do trying to push a 2.5 ton truck around the city...:skep:
     
  17. Rumplemenz

    Rumplemenz New Member

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    now im beginning to realize why i got my tahoe for 10k under sticker.. just a little info to everyone.. if you put on an avg of 12k-15k a year for every dime gas increases its 10 bucks more a month out of your wallet....
     
  18. D'Hag

    D'Hag Full Access Member

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    I'm always kinda surprised at the general misunderstanding about fuel octane.

    First, higher octane fuel does NOT burn more easily. To be as simple as possible, it has a higher flash point. That is, it's more resistant to spontaneous combustion from heat and pressure. Then, once it's ignited, it burns more slowly, building combustion pressure more slowly. That's why you can increase ignition timing advance with higher octane fuel. That's also why, if you use high-octane fuel in a low-compression engine that doesn't need it you get more unburned fuel, resulting in black exhaust system deposits and possibly burned-up converters.

    Second (read all of this before you react), it IS a myth that higher octane fuel increases MPG, IF the vehicle is not equipped with an oxygen sensor and programming to use it.

    Our Tahoes have knock sensors, and the ECU advances the ignition timing according to fuel octane. Basically, the ECU advances the timing periodically to test the knock sensor and to check the octane. Then it settles in on a timing advance that matches the fuel and operating conditions. THIS is what increases MPG with higher octane fuel.

    Optimum fuel economy and power, as they relate to ignition timing, is when the fuel is ignited at the best time to exert maximum down force on the piston during the power stroke, with minimum resistance to the piston when it's rising on the compression stroke.

    If the ignition fires too soon, then combustion pressure can build too fast, and resist the rising piston. So too much ignition advance can actually reduce power and fuel economy. Go even further, and you get knock. Old school tuners used to believe that you advanced timing right up to the edge of getting knock. Computers have shown that this is not quite right. The best is to go right up to the edge of knock, then back off 2 or 3 degrees of advance.

    If the ignition fires too late, then maximum force isn't developed in time to push the piston down.

    If your Tahoe is E85-capable, you can advance the ignition timing even more, and get MPG with E85 approaching what you get with pure gas. BUT (and this is important), since the octane of E85 is up around 105, AND ethanol burns cooler than gasoline, it's VERY easy to over-advance the ignition timing with E85 and never trigger the knock sensor or hear a knock. Then you're into that situation where the fuel is being fired too soon, killing power and economy.

    It's a balancing act. If your vehicle doesn't NEED higher octane and it doesn't have a knock sensor, then premium fuel is a waste of money, unless you can advance the ignition timing somehow. If it has a knock sensor and the right programming, and the compression to use it, then premium fuel will increase MPG, and might cost less per mile to operate. But if you over-tune the ignition timing, all the octane in the world won't get you more power and economy.

    Hope this helps understanding.
     
  19. akim47

    akim47 New Member

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    hmm... well the 6.2L denali "recommends" premium fuel, but does not require it... what does this mean? i've been rotating betweem 87 and 91... not sure if i notice any differences...
     
  20. 73shark

    73shark Full Access Member

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    It means that the engine is designed for its maximum performance using 91 octane. If you use 87 or 89, then the computer compensates by retarding timing to prevent knock and/or pre-ignition which decreases performance.