Poor MPG, tuneup maybe?

[98sierra4x4]

I have a 1998 Sierra 1500 4x4 with 3.73 gears, 4l60e, 265/75R16 tires and a 5.7 vortec. On my last tank of gas I got 9 mpg with 98% of that being city and 25 degrees F and below weather. Does this sound bad? oh and also when I first bought the truck it had the check engine light on and it was for o2 sensors but then the battery died and now the light is no longer on.

So for plugs and wires what brand should I get?
And what brand for o2 sensors should I get?

Thanks, Matt.

 

[poncho62]

Tune up....yes
O2 sensors....yes, at least the front 2

9mpg....sucks
You should be getting about 15

 

[SCOTTYINWV]

Do you let it idle warming up a lot?

 

[Mangonesailor]

I have a 1998 Sierra 1500 4x4 with 3.73 gears, 4l60e, 265/75R16 tires and a 5.7 vortec. On my last tank of gas I got 9 mpg with 98% of that being city and 25 degrees F and below weather. Does this sound bad? oh and also when I first bought the truck it had the check engine light on and it was for o2 sensors but then the battery died and now the light is no longer on.

So for plugs and wires what brand should I get?
And what brand for o2 sensors should I get?

Thanks, Matt.

Plugs: Platinum or just regular AC-delcos with a single electrode, and gap them to .045" (Unless you put a hotter coil on, then .050-.055" is good)
Wires: Taylor 8mm. Silicone insulated and good quality.

Check your cap and rotor button and air filter. How old is your fuel filter?

 

[98sierra4x4]

Tune up....yes
O2 sensors....yes, at least the front 2

9mpg....sucks
You should be getting about 15

Thanks for your input. Yeah something must be up


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[98sierra4x4]

Do you let it idle warming up a lot?

Yes i do, its been 20 and lower here in wi lately lol


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[98sierra4x4]

Plugs: Platinum or just regular AC-delcos with a single electrode, and gap them to .045" (Unless you put a hotter coil on, then .050-.055" is good)
Wires: Taylor 8mm. Silicone insulated and good quality.

Check your cap and rotor button and air filter. How old is your fuel filter?

Ok thanks, i have no clue how old the fuel filter is but i think i will replace it.


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[98sierra4x4]

I just pulled a plug and this is how it looks, should I replace it? Im thinking so.

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[Mangonesailor]

I just pulled a plug and this is how it looks, should I replace it? Im thinking so. [pic removed because huge]


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What was the gap?

 

[poncho62]

Plugs these days are usually good for 100K.....For the price of them, I would replace them.

BTW...you are saying how cold it is.....Winter time, vehicles get much worse mileage due to more idling and winter gas has additives to prevent freeze up. You mileage should get better in the spring, but a tuneup now wont hurt