Advice: 2009 Averaging 8.5 MPG (3 Viewers)

[Griffinstrings]

Hi, Recently picked up a 09 with 254k. I'm currently averaging 8.5 mpg on my 5 mile flat daily commute to work. I'm using 87 octane, babying the accelerator, and averaging around 45-50 mph on the commute. Have changed plugs, valve cover gasket, air filter, greased drive shaft, etc. I've ordered new fuel filter. There is a moderate lift and 295/75/17 Grapplers running 40 psi on the vehicle. Other than a possible valley plate issue, the vehicle drives perfectly. Any advice on troubleshooting the mpg would be greatly appreciated. Thanks! Chris in Birmingham, AL

 

[Sandroad]

That sounds about right for a very short commute on very large tires. How are you calculating mpg? If you’re doing it with no correction for large tire size, it will come out low. If you want to take further action (that I doubt will help much), see what others think about a new PCV valve, new oxygen sensors, or mass air flow sensor cleaning.

 

[Griffinstrings]

Thanks for response! I'm referencing the digital readout since last fill up. Good idea on the PCV valve.

 

[AZLX570]

250k+ miles, 34"+ aggressive(ish) tires, lifted, and under highway speeds? I'd calculate it by hand furst but ~10mpg doesn't seem too far out of the norm if that 5 miles is stop and go traffic. At under 5 miles it's probably barely getting up to operating temperature.

 

[Griffinstrings]

Thanks! I think mentally double digits are acceptable and single are not!

 

[Boston Mangler]

Unpopular opinion:

Larger tires alter speedo, which alters odo, which alters MPG calculations

Until speedo/odo is corrected, youll never get an accurate MPG calc

To test this, get a GPS, get it to 65mph, check speedo, put on stock wheels, do the same thing. It will all makes sense

 

[turbo8]

Hi, Recently picked up a 09 with 254k. I'm currently averaging 8.5 mpg on my 5 mile flat daily commute to work. I'm using 87 octane, babying the accelerator, and averaging around 45-50 mph on the commute. Have changed plugs, valve cover gasket, air filter, greased drive shaft, etc. I've ordered new fuel filter. There is a moderate lift and 295/75/17 Grapplers running 40 psi on the vehicle. Other than a possible valley plate issue, the vehicle drives perfectly. Any advice on troubleshooting the mpg would be greatly appreciated. Thanks! Chris in Birmingham, AL

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What fuel filter did you buy? US 200's didn't come with fuel filters, it has a mesh sock inside the tank though.

Are you brakes dragging?

 

[gaijin]

Hi, Recently picked up a 09 with 254k. I'm currently averaging 8.5 mpg on my 5 mile flat daily commute to work. I'm using 87 octane, babying the accelerator, and averaging around 45-50 mph on the commute. Have changed plugs, valve cover gasket, air filter, greased drive shaft, etc. I've ordered new fuel filter. There is a moderate lift and 295/75/17 Grapplers running 40 psi on the vehicle. Other than a possible valley plate issue, the vehicle drives perfectly. Any advice on troubleshooting the mpg would be greatly appreciated. Thanks! Chris in Birmingham, AL

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I was going to do a simple calc to adjust for your tire size, but I cant find "295/75R17" tires anywhere. Are you sure about that size?

 

[grinchy]

I get around 10 in the city. The digital gauge will show between 8.5 and 10. Usually shows 12 or less on the highway.

Actual is 8% higher, I’m running 34.5” (35x10,5x17) tires and have 4.88 gears. The gears don’t change the odometer like the tires do, but they do make driving fun again.

 

[LX Cruiser]

I'm currently averaging 8.5 mpg on my 5 mile flat daily commute to work. I'm using 87 octane, babying the accelerator, and averaging around 45-50 mph on the commute.

That sounds off to me. How long does your truck typically idle before you leave? That is factoring in an mpg of 0. Sitting at long stoplights does the same thing...

Also wondering if you've got a parking brake dragging

 

[gaijin]

Hi, Recently picked up a 09 with 254k. I'm currently averaging 8.5 mpg on my 5 mile flat daily commute to work. I'm using 87 octane, babying the accelerator, and averaging around 45-50 mph on the commute. Have changed plugs, valve cover gasket, air filter, greased drive shaft, etc. I've ordered new fuel filter. There is a moderate lift and 295/75/17 Grapplers running 40 psi on the vehicle. Other than a possible valley plate issue, the vehicle drives perfectly. Any advice on troubleshooting the mpg would be greatly appreciated. Thanks! Chris in Birmingham, AL

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I was going to do a simple calc to adjust for your tire size, but I cant find "295/75R17" tires anywhere. Are you sure about that size?

In the absence of a response, just to give an example of how a different (larger) tire size can adversely affect mileage compared to the stock tire, let's assume you are actually referring to a LT285/75R17 Nitto Recon Grappler A/T tire:

Stock tire is 285/60R18 which has a nominal Revolutions per Mile spec of 661

Your tire is 285/75R17 which has a nominal Revolutions per Mile spec of 614

661-614 = 47 / 661 = 0.07 (or 7%)

Which means the 285/75R17 tire will rotate 7% fewer revolutions per mile than the stock tire.

While the data on your dash thinks your truck has gone 100 miles based on the diameter of the stock tire, it has actually travelled 7% more, 107 miles, on your larger tires.

So... just based on tire size alone, when you calculate an average MPG of 8.5 MPG based on data from your dash, the actual average MPG is 8.5 * 1.07 = 9.1 MPG.

But, as has been mentioned, the best way to find out exactly what your MPG is would be to measure distance with a standalone GPS unit, and keep accurate records of fuel added at each fill-up. Mo' data, mo' betta.

HTH