Gas Mileage Question

Both my father and I have the same model trucks, his is a 03 mine 2000, both LT's, extended cab, 5.3 etc. same gear ratio 3.42 only difference is mine has a posi. and his does not. Questions is why does he get 17-18 mpg where I get 13-15, can the rearend make a difference? If so explain.:uhoh:

Both my father and I have the same model trucks, his is a 03 mine 2000, both LT's, extended cab, 5.3 etc. same gear ratio 3.42 only difference is mine has a posi. and his does not. Questions is why does he get 17-18 mpg where I get 13-15, can the rearend make a difference? If so explain.:uhoh:

my 2000 sil LT ext cab 4X4 has the locking diff with the OEM 3.73 ratio ...MPG with dino oil was max. 18 MPG ...with synthetic max 19 + MPG...

3.42 ratio 2wd ???? If your getting 13-15 mpg with 2wd you have a problem ,,,things like aftermarket exhaust , cat converter , O2 sensors, maf dirty, air filter , heavy right foot ....

my 2000 sil LT ext cab 4X4 has the locking diff with the OEM 3.73 ratio ...MPG with dino oil was max. 18 MPG ...with synthetic max 19 + MPG...

3.42 ratio 2wd ???? If your getting 13-15 mpg with 2wd you have a problem ,,,things like aftermarket exhaust , cat converter , O2 sensors, maf dirty, air filter , heavy right foot ....

Aftermarket exhaust like flowmaster doesnt help with gas mileage, airaid intake etc.....they actually hurt gas mileage?

Do you have over-sized tires? That could make a difference also in MPG calculations. My 2000 silverado mpg has dropped recently also and not sure what could be causing it. I have no check engine lights and have cleaned my MAF and it runs really well. Not sure what else to check. BTW...I was getting 15 in the city easy and now down to 13 or so.

My 2002 has the computer that "lears" your driving habits and adjusts shifting accordingly. Jcat may or may disagree, I'll throw it out there... Disconnect the battery for 30 minutes to reset the computer(s) and then give it a shot for a week and see if they still differ by such large amounts.

My 2002 has the computer that "lears" your driving habits and adjusts shifting accordingly. Jcat may or may disagree, I'll throw it out there... Disconnect the battery for 30 minutes to reset the computer(s) and then give it a shot for a week and see if they still differ by such large amounts.

I don't think the pcm learning would effect MPG that much...

however his father gets better MPG ...

my opinion is: younger drivers have a heavy right foot...then " IF " he has an exhaust with a nice sounding muffler, this wanting to hear the rumble of power is also a MPG killer....

Open road versus in town can make 3 - 4 mpg difference easily. How you accelerate from a stop can make a 1 - 2 mpg difference. Winter blend fuels can have an adverse affect also.

number of things can come into play, maybe your air filter is dirtier than his, i would have to say age of the drivers is a difference, younger drivers wanna get where they are going quicker (harder take offs, and higher driving speeds). Age of the vehicle, how the previous owners drove them, different tire pressure, I'm sure that both of you don't take the exact same roads when you do go somewhere. Is his garage kept and yours outside? This time of year if/when you let your vehicle warm up could mess with it, the list could keep going on and on.

Does a flowmaster really make a difference on gas mileage? I noticed my 00 4.8 went down about 2-3 mpg, but i didn't point the finger at the exhaust because it sounds good. All I did was swap out the oe muffler for 40 series. I guess thats what you give up to make some noise. right now I get about 14-15 mpg if i take it easy. it doesn't seem to change much if i push it hard. oh well this snowy northeast really sucks. come on summer.