1999 Silverado

[Badshot]

I have a 1999 5.3l z71 and im only getting 13mpg i have added a cold air intake and still have crappy mpg, even when driving it easy What can i do to improve it? Next i have a service engine light on, its code 446 i think... the evap code. anyways i replaced the EGR valve thinking it was it -_- Well its till on... Gas cap is tight as well what can i do to fix this?

[amtz.zero]

13 mpg isn't... that.. bad.. I get an average of 17 mpg. But I have the 4.8L V8. Are you driving mostly in the city? There are a lot of things that can contribute to your bad fuel economy. City driving, winter gas, maintenance not up-to-date, etc.

[Badshot]

Well actually about 2 miles in the city to every 13 miles in the interstate. lol it takes me a mile to get to the interstate and work is a mile off the interstate haha

so mainly interstate

[Nytemare]

Well actually about 2 miles in the city to every 13 miles in the interstate. lol it takes me a mile to get to the interstate and work is a mile off the interstate haha

so mainly interstate

Also... what speed are you hitting on the interstate....anything above 55-60 and your fuel consumption goes through the roof. That's why you see a lot of semi trucks with a sticker on them saying that they travel 55 for optimal fuel economy.

 

Your gearing, tire size, tire thread that has a huge impact on economy too. Your evap code is probably due to a bad vent valve or worst case a cracked evap can.

[Badshot]

oh snap.. lol i go about 70-75 cruise set on interstate. wow... i thought in a 5.3 v8 that would be a good speed. guess i was wrong and also i have 285-75-16 on my truck mickey thompson wheels and a cold air intake. I hurd that having the check engine light on also will lose gas millage because it only uses the bare minimum of the computer when its on... so called it goes into limp mode?