Gas mileage

Jacob Metz said:

2001 Tahoe 5.3 4x4 factory gears

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CountryBoy19 said:

There are at least 3 factory gear ratios available. GU6=3.42, GT4=3.73, GT5=4.10

Also, you didn't answer the question about how you're calculating mileage. As stated, with an oversize tire, unless you reprogram for that tire size you are physically travelling more miles than your odometer indicates (you're also travelling faster than your speedometer indicates). Therefore, you need to adjust your mileage numbers with hand-calcs, use a gps to track miles-travelled, or have it reprogrammed for that tire size. Until it's reprogrammed the DIC information is completely useless without doing some maths. You should be able to find info on revolutions/mile on the stock tires vs your oversize tires and scale the numbers.

FWIW, stock size tires, 5.3L 4X4, 4.10 gears I get right around 16 mpg

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Jacob Metz said:

Alright I run the truck completely empty then fill up. Then I run empty get totals miles ran divided buy how many gallons used.
And as for gear I believe it 373

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Jacob Metz said:

Alright I run the truck completely empty then fill up. Then I run empty get totals miles ran divided buy how many gallons used.
And as for gear I believe it 373

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CountryBoy19 said:

HOW are you getting the number of miles you drove between fill-ups? From your odometer? Did you get your speedometer recalibrated when you changed tire size? If not your odometer readings are completely useless. So your calculated mileage is just as worthless. The only way to get good numbers is to use a GPS to track distance or have it recalibrated.

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Martinjmpr said:

Do you know what ratio? It should be on the RPO code sticker on the dash. Also you can create an account with GM and they will send you a build sheet that shows all the options your vehicle has based on the VIN.

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Wolfbraid said:

I have an account with GM, was curious where to look on the site? I couldn't find anything regarding build sheets.

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Martinjmpr said:

I'm resisting the impulse to say "sell it and buy a Prius" but I actually do get it - when you have to pay for gas, it makes sense to get the best MPG you can.

To answer your question realistically, we need more information. Year? 2wd or 4wd? Miles? Gear Ratio? What other mods do you have?

What kind of driving are you doing? Stop-and-go city or suburb driving? Long highway miles? With a vehicle as heavy as these, stop-and-go will kill your MPG no matter what else you do.

Also how are you calculating your mileage? If you're going by the DIC readout consider that unless you have re-calibrated your speedo and odo that is going to give you an inaccurate rating. Also, the DIC is not really a good way to determine actual MPG anyway, to do that you need to hand calculate.

If you want to accurately measure MPG the first thing you have to do is figure a way to calculate your actual miles driven.

Here's how I did it on my Suburban after I put bigger tires (33's) on: Get a GPS mounted. Then go to the trip meter on the GPS. Set the GPS trip meter to 0, and set the truck trip meter to 0 also.

Drive at least 100 miles with the GPS on (more is better.) Make sure the GPS is always recording mileage driven. After at least 100 miles compare the two. If you have oversized tires, likely the GPS will show more miles than the truck odometer (because your bigger wheels have a greater circumference the odometer only knows how many revolutions your driveshaft is turning, not how many miles you are actually going.)

Compare the two numbers. Let's say the truck odometer shows 350 miles and the GPS shows 360.3. 360.3 / 350 = 1.03. That means that from now on, you have to multiply the truck's odometer reading by 1.03 in order to get an accurate distance.

Set the truck odometer to 0 when you fill the tank. Drive as normal. When it's time to refuel, fill the truck up and write down the number of gallons it took to fill the truck. Multiply the miles x 1.03 (or whatever your multiplier is) to get actual miles driven and divide by gallons used. That is your ACTUAL mileage (as opposed to what's on the DIC.)

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