88 suburban mileage

howdy folks, new to the forum and had a question, i've recently purchased an 88 suburban, its mostly a project vehicle so i'll have lotsa questions to come but for now just these 2.

what should i expect as far as mileage?

there's a lot of mods, and a lot of variables in it but i feel it should be better than what it is, i get 6 mpg.

from what i've seen in the forums the o2 sensor seems like it could dramatically drop the mpg and possibly not throw the check engine light, my other question is where might i find the o2 sensor?

now for the mods:
3"body lift,
6" suspension lift.. i think,
35" tires,
its also sitting on 1-ton rears rather than stock

engine: 350
tranny: 400
v20
i unfortunately havent checked out the gearing as of yet either, so any insight would be greatly appreciated, thanks in advance

howdy folks, new to the forum and had a question, i've recently purchased an 88 suburban, its mostly a project vehicle so i'll have lotsa questions to come but for now just these 2.

what should i expect as far as mileage?

there's a lot of mods, and a lot of variables in it but i feel it should be better than what it is, i get 6 mpg.

from what i've seen in the forums the o2 sensor seems like it could dramatically drop the mpg and possibly not throw the check engine light, my other question is where might i find the o2 sensor?

now for the mods:
3"body lift,
6" suspension lift.. i think,
35" tires,
its also sitting on 1-ton rears rather than stock

engine: 350
tranny: 400
v20
i unfortunately havent checked out the gearing as of yet either, so any insight would be greatly appreciated, thanks in advance


to be sure this vehicle has a very large appetite . I would expect 10-12 MPG...

the o2 sensor and a defective cat will greatly reduce mileage...
the upsteam O2 is on the exhaust prior to the cat....replace with the correct type so check that ,, the new sensor is correct with you vin #...as the one that is in there maybe incorrect..checking for restricted cat is done when the o2 is removed the the exhaust pressure can be measured...


over sized tires will also cause MPG losses...as well as increased vehicle height/weight...

when gas goes to 10.oo/gal good luck...

I have a 89 v2500 4x4 with a 350. Everything is stock on the drivetrain, but i have a performance exhaust system and installed manual locking hubs on it. Doing 65 down the highway I average 15mph. Around town I am lucky to get 13mpg.

Hope this helps

Colby