TBI gas mileage, am I doing it wrong?

[350chevy719]

So I've been reading around and people are getting anywhere from 10 to 14ish city. And I'm over here getting 8-9 on a good day city. I don't do enough hwy driving to gauge it. I'm stock height with 33s on 20x12s. Open air cleaner, y-pipe to Flowmaster 10 dual 2 3/4 out. 190k miles. Is that mileage what I should be expecting or could I have an issue?

 

[daturbosix]

i get about 14/15 around town here. maybe a blast down the highway or 2 on a tank.

 

[90halfton]

Alot of ppl seem to have mileage issues around town with 33" tires, hmmmmm. What gears are you running?

 

[Texcuda]

33" tires are pretty tall for the gutless motors in these trucks especially if you haven't addressed the rear gears for the taller tires.

 

[350chevy719]

Alot of ppl seem to have mileage issues around town with 33" tires, hmmmmm. What gears are you running?

I'm not sure off the top of my head what gears. Which rpo would I need to check?

 

[350chevy719]

What's going to happen when I throw 9in and 37s on it! Yikes!!

 

[slowburb]

The tires.

 

[90halfton]

I'm not sure off the top of my head what gears. Which rpo would I need to check?

Sticker in the glove box assuming they've never been changed. Can jack up the rear of the truck, mark the tire placement against a certain place on ground, mark driveshaft ujoint or yoke in reference to a mark on differential. Now spin driveshaft and count number of turns of driveshaft vs number of turns of tire and that is gear ratio. For example, 3 3/4 turns of shaft for one revolution of tire is 3.73:1 ratio. If youre running too small of gear with too big of tire the truck will be lugging around town, and sucking fuel. Not to mention not as much fun to drive.

 

[90halfton]

What's going to happen when I throw 9in and 37s on it! Yikes!!

Awesomeness when setup right

 

[350chevy719]

Sticker in the glove box assuming they've never been changed.

Which code for the gears? I doubt they've been changed. When I got the truck it was bonestock. I have all the paper work for stuff done to the truck by previous owners.