2002 chev. 1500 fuel milage

I have a 2002 chev silverado with 100,000 km on it with the 4.8L and auto trans. I consistantly get an average of 12.5 mpg. I still have original spark plugs, air filter (filter vacuum gauge is still in green area) fuel
filter etc... The truck runs perfect so I see no need to start changing things like these and the manual does not say to in there maintenance schedule. The epa estimates for that truck are 18 city/22 highway. and I do about 60% highway. Is this normal and the estimates are inflated?
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You ask this at 100k, untouched, help yourself here and do some maintenance!!

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Over the life of my 2002 ext cab with a 5.3 auto has been 16.45. I use excel to keep track. All my driving is in city. Two trips on highway were 19.8 and 18.3.

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what do you suggest, like I said I am doing what the manual says.

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100k on the a/f. That is not in the maintenance guide!!! If there was a problem with fuel mixtture or fuel control sensors the CEL would be on, so it is temperature, state of tune or driving habits/conditions.

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wrote:

You do not mention what tire size and type you have which can be a BOG factor in MPG as well as the way you drive and the terrain you drive in. BTW, if you read the actual EPA test cycle for highway MPG, they never exceed 60 and the average speed for the 12 minute test is 48MPH. Nobody averages 48 on highway except maybe in a city at rush hour (if that) but it is how they weight the test to their favor for marketing. If they used a higher more realistic standard, the "ratings" would be lower. Newer test standards are in the works and while some claim could MPG with those trucks, you have a lot of weight/mass there and it take fuel to move it.
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I should have mentioned that, I have 235-85-16 mud grip tires and it is winter here (20 F).

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I think those are small diameter tires than standard for that truck. There may be a speedometer discrepancy.
Dave
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Greetings,
I think you've partially answered your own question right here. EPA mileage is determined with stock sized tires with a narrow street tread in a climate-neutral environment. Adding tires of a significantly different size/width and a tread designed to grip soft terrain will lower your mileage. In addition, I've seen air filters almost fully plugged with only a minor change on the air flow indicator.
Here's some free advice. Do a lot of basic maintenance like air filter, fuel filter, PCV valve, crankcase breather filter (if it has one). New plugs and a basic tranny service with new fluid and a filter won't hurt either albeit may not be absolutely necessary. Check your tires for proper inflation pressure (low pressure can cause you to lose MPG). Run a street tread in the warmer months and don't bother to measure mileage in any conditions where your tires have to push their way through snow.
If your current tires are a different overall diameter than what came stock, take your truck to the dealer and have them reflash the computer for the current tire size because a speedometer error can be giving you false readings when you calculate MPG.
And finally, I'm not saying that you have any of these habits but you should drive conservatively - avoid jack-rabbit starts, hard stops and frequent braking. Tailgating and other poor driving habits requires frequent use of your brakes, which in turn requires more frequent use of your gas. And finally, don't ride your brakes (keep your left foot on the brake and your right foot on the gas).
Cheers - Jonathan

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SnoMan wrote:

I get the EPA estimates with my 04 driving at 65mph so why can't an 02?
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mark wrote:

It could be normal. What you don't say is:
-has the mileage always been like this or is it slowly getting worse? (need a tuneup) -your average highway speed is 85 mph. (probably normal fuel economy at that speed.) -uphill in the mountains towing a boat (you're getting good fuel economy.)
Ray
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