5.3L 3.42 vs 3.73 fuel economy?

[ryeguy]

Hi all,

 

I'm hoping somebody can post real-world economies for the 5.3L with the max tow package. I can't find one on the lot around here.

 

I took a new 5.3L with 3.42's for a test drive, set the cruise at 110kph (about 70mph) and flat ground and it didn't meet the EPA rating because it would never enter V-4 mode. The 4.3L with 3.42's was about 10% better than the 5.3L too (it wouldn't enter V-4 mode either). I'm wondering if the 3.73's (my preference) may do as well, or possibly even better unloaded because even though the engine is turning faster, it may be able to drop into V-4 mode easier (and save fuel) because it's closer to the torque and hp peaks.

 

Thanks!

 

--Rob

[bronco351]

I too was wondering about these things. I'm guessing that the 3.73 should enter v4 mode easier, but it might have to be at a slightly lower speed. It is hard for me to suggest any information about this as I am not an owner (yet).

 

3.73 should get better mpgs in the city though because the engine has to work less to accelerate.

 

You problably wont reach epa on a test drive because new motors have a break-in period. This is common for all vehicles.

[iCryWheniGoPoop]

My truck has 308's and hits V4 easily at 80mph, so I'm going to have to agree with the previous poster.... Probably just needs broke in.

[bboyce536]

From my experience, cruise will never meet epa unless in a tail wind. I find sometimes after you learn the truck you can coax it into v4 mode often Once you get up to speed simply by letting off the gas slightly.

 

Unless you are in a headwind, 70mph should be no problem to hold v4 mode.

[calgator73]

I have the 5.3 3.73. At 70-75 I have no problem with V4 mode. Over 75 it happens very seldom. I posted this in a different thread awhile back. At 75 from Hampton to Richmond on 64 I pulled 18.5. Way back at 70 I pulled 20.5. More recently, around town if I drive the speed limit and moderate my acceleration then I get 15-18 when it's over 45-50 degrees. Temps in the 30s it sticks in the 13s. I'm taking a trip to Knoxville going West I-64 and I-81 to I-40 followed by a trip down 95 to Hilton Head. I'll post updates when I'm back.

[KARNUT]

I have less than 3000 miles, Houston to Fairfield tx 5.3 345, at 79 Mph. The truck went into V4 often 19 miles per gallon for the trip, on top tier gas. Running corn now.

[ryeguy]

Thanks guys! This is exactly the info I'm hoping for. It sounds like the 6.2L is really economical too...it's a shame they don't tie that motor to the SLE interior.

[iCryWheniGoPoop]

I have less than 3000 miles, Houston to Fairfield tx 5.3 345, at 79 Mph. The truck went into V4 often 19 miles per gallon for the trip, on top tier gas. Running corn now.

!!!!WARNING!!!!

If you are a HP junky, it's going to be hard to go back.

[KARNUT]

My other truck is a 92 Chevy 383, dart heads whipple sc, stage 2 trans, 373 gear, beast. Wife drives a Geneses , her toy is an Acura intagra r. She's as bad as me. I'm a bad influence. The gmc is the slow one for now.

 

 

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[iCryWheniGoPoop]

My other truck is a 92 Chevy 383, dart heads whipple sc, stage 2 trans, 373 gear, beast. Wife drives a Geneses , her toy is an Acura intagra r. She's as bad as me. I'm a bad influence. The gmc is the slow one for now.Sent from my iPhone using Tapatalk

Oh yeah, you will hate switching back then, even though it is your put put in the family. Even though the power is subtle when switching to E85, it seems massive coming back down. It's like crack.... Awesome till you run out. Unfortunately I have an E85 drug dealer hanging out on the corner every day on the way to work so the convenience makes it even harder.

[KARNUT]

My other truck is a 92 Chevy 383, dart heads whipple sc, stage 2 trans, 373 gear, beast. Wife drives a Geneses , her toy is an Acura intagra r. She's as bad as me. I'm a bad influence. The gmc is the slow one for now.Sent from my iPhone using Tapatalk

Oh yeah, you will hate switching back then, even though it is your put put in the family. Even though the power is subtle when switching to E85, it seems massive coming back down. It's like crack.... Awesome till you run out. Unfortunately I have an E85 drug dealer hanging out on the corner every day on the way to work so the convenience makes it even harder.

I got one 3 miles away, I notice the improvement already. I'm going to try to put 10,000 miles on the truck before any real mods, thanks to this website make sure there no bugs.

 

 

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[Ulukslo]

My other truck is a 92 Chevy 383, dart heads whipple sc, stage 2 trans, 373 gear, beast. Wife drives a Geneses , her toy is an Acura intagra r. She's as bad as me. I'm a bad influence. The gmc is the slow one for now.

 

 

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Karnut what kinda times does your 92 truck run? And what weight gear and body is it?

[KARNUT]

My other truck is a 92 Chevy 383, dart heads whipple sc, stage 2 trans, 373 gear, beast. Wife drives a Geneses , her toy is an Acura intagra r. She's as bad as me. I'm a bad influence. The gmc is the slow one for now.

Sent from my iPhone using Tapatalk

Karnut what kinda times does your 92 truck run? And what weight gear and body is it?

The family bis. got moving in the 90s last car I took to the track was a impala ss. The rods after were just street toys. The truck has 373 gear, I have pic in the photo section in other rides.

 

 

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[iCryWheniGoPoop]

The family bis. got moving in the 90s last car I took to the track was a impala ss. The rods after were just street toys. The truck has 373 gear, I have pic in the photo section in other rides.Sent from my iPhone using Tapatalk

Hell yeah @ impala ss.. I have a track video on this forum somewhere of me in mine.

 

What's this topic about again?

[KARNUT]

Hell yeah @ impala ss.. I have a track video on this forum somewhere of me in mine.

 

What's this topic about again?

For some strange reason Impalas were my chosen rides, till they when front wheel drive Ive had 17 or more. The Geneses we have know comes the closest. got my eye on the new ss, its a little to loaded for my taste. The fastest one I built was a 74 impala, we had a salvage your at the time. It had a 454. 700R4 trans, 373. It was my wifes DD. The ground would shake when you started it. Now you see why I been married 40 years. Some of the cars she would drive so I could feed my addiction was unreal. When the kiddes got in school and she started working, she started driving sport cars.