Gas Mileage 5.3 3.42 vs 3.73

Ridersfan · May 3, 2017

3.08 gearing is harder on fuel that 3.42 gearing... to the argument that a 3.73 HAS to be worse than 3.42 is invalid.

It boils down to load, not to RPM's

bronco351 · May 3, 2017

I have a 2014 5.3L with the 3.73s. I currently have 285/70r17 tires, and they dropped my mileage.

Before tires i got about 18/24mpg city/hwy

I now get about 15/20 with the bigger tires. Winter is about 20% worse.

My last truck was an f150 with 3.55. It had great mileage on the highway, but really struggled with a trailer that was about 50% of the tow rating.

I feel that the lower ratios are better for highway, but make the engine work more when accelerating or towing. I would be surpised if there is a difference in the "real world"

5RWill · May 3, 2017

I have a 2014 5.3L with the 3.73s. I currently have 285/70r17 tires, and they dropped my mileage.

Before tires i got about 18/24mpg city/hwy

I now get about 15/20 with the bigger tires. Winter is about 20% worse.

My last truck was an f150 with 3.55. It had great mileage on the highway, but really struggled with a trailer that was about 50% of the tow rating.

I feel that the lower ratios are better for highway, but make the engine work more when accelerating or towing. I would be surpised if there is a difference in the "real world"

That's still pretty good numbers. I take the long way home after work so i can see my MPG break 14 lol. Maybe toyos ares just too damn heavy. With 3:42s of course. Bronco is yours tuned? That's my next step is headers and then tune.

bronco351 · May 3, 2017

That's still pretty good numbers. I take the long way home after work so i can see my MPG break 14 lol. Maybe toyos ares just too damn heavy. With 3:42s of course. Bronco is yours tuned? That's my next step is headers and then tune.

I have bfg all terrains. They are much heavier than the stock tires. No tune or other upgrades.

5RWill · May 4, 2017

I have bfg all terrains. They are much heavier than the stock tires. No tune or other upgrades.

Running premium or pure gas? Or just regular unleaded? Any decent all terrain or decent tire for that matter are much heavier than the SR-As i was just singling Toyo out because 295/70/17s across the board in the RT/MT are nearly 70lbs or so, at 68lbs for 295/70r17 and 64lbs for 285/70r17. Maybe mine just likes fuel. Air dam removed?

dman1458 · May 4, 2017

Rear ends between trucks is relative to them. My Titan has 3.36 gears and I'm lucky to get 13 MPG in mixed highway/city and I have not been able to get better tan 15 MPG straight highway. Other guys have a 2.94 rear ends in Titans and get maybe 1.5 better. The new titans have 2.94 gears and do get better mileage, but only 30% as claimed by Nissan.

mookdoc6 · May 4, 2017

Rear ends between trucks is relative to them. My Titan has 3.36 gears and I'm lucky to get 13 MPG in mixed highway/city and I have not been able to get better tan 15 MPG straight highway. Other guys have a 2.94 rear ends in Titans and get maybe 1.5 better. The new titans have 2.94 gears and do get better mileage, but only 30% as claimed by Nissan.

I work with a guy who owns a older Titan.....He told me it's never gotten 16 mpg's on Hwy and do not but a Nissan truck. Although the new one doesn't seem to bad? I just dislike Nissan in general and my wife drives one.

Edited May 4, 2017 by mookdoc6

dman1458 · May 4, 2017

I work with a guy who owns a older Titan.....He told me it's never gotten 16 mpg's on Hwy and do not but a Nissan truck. Although the new one doesn't seem to bad? I just dislike Nissan in general and my wife drives one.

He is not wrong on anything he said. I like the truck, but far too many niggles with it.

5RWill · May 4, 2017

FWIW the Titan and Tundras for that matter are absolute guzzlers. Even the recently reviewed 5.0 cummins wasn't doing that well for the Titan. I see a lot of people that love their titans just like the tundra owners but comment on it guzzling gas. It comes something like this "I loved that truck, it would pull like a monster, but i got 11.5mpg in town and 14mpg on the highway."

lawn boy · May 4, 2017

That's still pretty good numbers. I take the long way home after work so i can see my MPG break 14 lol. Maybe toyos ares just too damn heavy. With 3:42s of course. Bronco is yours tuned? That's my next step is headers and then tune.

The Toyo RT's ARE heavy. My 285/55/20 RT's on 20" denali takeoffs are EASILY double the weight of my stock 17's on bridgestones. My MPG hasnt crested above 14.6 since i put them on with the leveling kit lol

UplandPa · May 4, 2017

If it were a clean sheet of paper I would go with the 3.73, however if the truck I was looking at had everything I wanted except that ratio and it had 3.42 and not the 3.08 I would not hesitate to buy the 3.42 geared truck.

You are going to be VERY happy with your GM truck, they are hands down the best trucks on the road!

kammi10 · May 4, 2017

The Toyo RT's ARE heavy. My 285/55/20 RT's on 20" denali takeoffs are EASILY double the weight of my stock 17's on bridgestones. My MPG hasnt crested above 14.6 since i put them on with the leveling kit lol

note to self.. do not buy those tires

5RWill · May 4, 2017

note to self.. do not buy those tires

That's not to discount from the tire though. It's a phenomenal tire, just have to run it low which i do. I could get better MPG if i ran 40+ PSI but i wont do it. Rides worse and the shoulder lugs don't make contact very well in mud/dirt. Lets be frank these trucks are in dire need of a tune from the moment they get off the production floor. GM tunes them like they're catering to 75 year olds nearing retirement. Once you free up the power a little with a tune and maybe some bolt-ons, MPG is not that bad. I say this on the basis of my cousin running his 295/70r17 Toyo MTs in his BB tuned 09 vortec and has bested me in mpg before i even got my RTs.

The other side is just that Toyo builds a tough heavy tire. I knew that going in, there is a reason Toyo is usually first in ratings for tread wear warranty, that comes with a price. Lastly moving from a 31" tire to a 33.5" tire especially with more aggressive tread, which is literally anything. The SR-A these trucks come with is the most useless truck tire i've come across. It's just a compromise really. Don't get me wrong i wish i got better MPG at times, but i like i've said several times in this thread. I'm driving a 5000lb+ 4WD truck just 1/2 an inch away from 34" tires with decent ground clearance, it ain't gonna happen.

And that ladies and gentlemen is how i justified the need for headers and the want for a cam...lol

MiamiSilverado1500 · May 30, 2017

If it were a clean sheet of paper I would go with the 3.73, however if the truck I was looking at had everything I wanted except that ratio and it had 3.42 and not the 3.08 I would not hesitate to buy the 3.42 geared truck.

You are going to be VERY happy with your GM truck, they are hands down the best trucks on the road!

My 2015 1500 5.3L has 22x9.5 and 32ish inch tires with 3.42 and I get mpgs in the mid to high 20s on the highway. I have a bed cover, MIT tube and muffler delete with no tune. Going by my tire measurements previous and now with current gears I should be running 3.73s after all the math is done. I saw a video on youtube for it and calculated myself and that's what I got. Originally I had the factory 20s with factory size tires so to be clear as a reference point.

Champion-Ship · May 31, 2017

If it were a clean sheet of paper I would go with the 3.73, however if the truck I was looking at had everything I wanted except that ratio and it had 3.42 and not the 3.08 I would not hesitate to buy the 3.42 geared truck.

You are going to be VERY happy with your GM truck, they are hands down the best trucks on the road!

Mine is a 3.42 All Terrain. Not a bad ratio.