GMC 5.3

[orviskid]

how is the 5.3 with the fuel management system?? i'm getting a new one and the saleman was pushing this for gas mileage. sounds good, but i doubt the mileage is any better. i have a 4.8 now and have had no problems. is the 6 speed tranny really good on gas??

[Stevens08]

Well this is tough to answer. The 5.3's are indeed better on gas than the 4.8's. The 6 speed tranny helps too. I know guys who average around 21 on backroads, and guys that average 16. If driven properly, the 5.3 will be better than the 4.8. Is it a lot better? No. But it is noticable. I'd reccomend the 5.3. I have the 6.2 and get about 15.4 average. 17.5 highway, about 13-14 city.

[MikeNH]

I've gotten a tank average of 20 once in 31000 miles and 1.5 years of driving. Typical average is 16-18 mpg overall but I do drive a bit fast on the freeway. 6 speed probably helps with efficiency but the biggest gain to me is driveability. The 5.3 seems sooooo much more responsive with that trans than a 4 speed. You're also not having to drop to so low a gear to pass on the highway which is nice too.

[vkjohnson]

agree with everything so far. 16-18 driving fast on the freeway. You can hit the EPA estimate of 21 mpg if you can keep to speeds of 55-60, but your average overall will never get there. I also tuned mine to change torque converter settings and gave me a 1 or 2 mpg bump to help. I do love the 6 speed, and the 5.3 is a good balance of power and fuel mileage IMO. That said, can't wait to try out a 6.2 sometime.

 

...and the AFM...you can hardly notice it cutting back and forth from 4 to 8 cyl. It is very smooth, but in reality it only cuts to 4 cyl if coasting, going downhill, or with a big tailwind.

[orviskid]

thanks, looks like i'll be trying it. i've seen alot of horror stories on here also about the AFM and the mileage. my truck now is really good, i hate to be going to a clunker. i'm switching for the 4x4 cuz mine doesn't have that now.i've been a solid GM fan, this would be my 3rd truck. This site scares the snot out of me though.a lot of issues with the GM's. cross my fingers and toes. i want the truck for the long haul, i don't want it in the shop every day.

[MikeNH]

Keep in mind the 5.3 is by far the most popular engine in the trucks, millions of AFM engines have been built and what you see here is only a puny proportion of what GM makes- they make somewhere north of 400,000 trucks a year and there are probably a few dozen people who make it here to report in, never mind the hundreds of thousands who have no issue so they won't be coming here to get help or complain. Taking the hit in power and losing the 6 speed because of what is realistically a few people is absurd to me. If you're that wary of AFM at least try to find a 6.2.

[Svenleven]

I had an 08 Sierra with the 5.3l and 4 speed and on the same 5 hour highway road trip I make several times a year, I was always averaging 14.0l/100km (works to 16.8 mpg US). With my 6.2l with the 6 speed, my last 2 trips where 12.8l/100km (18.3mpg US). This is driving ~120km/hr and passing from time to time. The conclusion I draw from this is the 6 speed making a significant difference. I imagine with the 5.3l, you would get at least a little better. In 4 years and 113000km, I never lost a drop of oil in it either, for all the stories you hear on here about oil consumption. I don't think the AFM does anything noticeable the fuel mileage in my opinion.

 

I would get the 5.3l 6 speed over the 4.8l 4 speed in a heart beat.

 

That said, I never really track city mileage cause it's so hard to be consistent to compare, but the 6.2l seems a little thirstier then the 5.3l there. Which is too be expected. Not sure how the 4.8l would compare there.

[jdubub]

5.3L with the 6 speed should be the one you look for at least. That or the 6.2L with the 6 speed.

 

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[Zembonez]

I much prefer the 4.8. Exactly the same engine architecture and none of that pathetic AFM garbage and no worries of the part failures and oil consumption of the 5.3. Mine is tuned and I have heavy 20 inch wheels... still averaging 17.6 mpg in mixed driving over the last 10K miles and I'm not all that easy on it.

[grogol]

I have a 2007 Sierra with the 5.3 and AFM. 60K miles and no engine issues. I have also put about 1000 or more miles on several 2009 and 2010 Silverado rentals with the 4.8 engine. The 4.8 downshifts a lot more on hills when I was driving on interstates where my Sierra never downshifts - annoying.

[BlackZ71Silverado]

If you are getting a new truck for anything other than a grocery getter, stay away from that small 4.8L. Either the 5.3 or 6.2 are the only ones to consider when getting a truck. The 4.8 is a dog compared to the 5.3, even with a tune it's not the same. Our 4.8 trucks at work are terrible, might as well get a V6.

[txab]

I have a 2007 Sierra with the 5.3 and AFM. 60K miles and no engine issues. I have also put about 1000 or more miles on several 2009 and 2010 Silverado rentals with the 4.8 engine. The 4.8 downshifts a lot more on hills when I was driving on interstates where my Sierra never downshifts - annoying.

 

That could also be transmission programming

[Zembonez]

If you are getting a new truck for anything other than a grocery getter, stay away from that small 4.8L. Either the 5.3 or 6.2 are the only ones to consider when getting a truck. The 4.8 is a dog compared to the 5.3, even with a tune it's not the same. Our 4.8 trucks at work are terrible, might as well get a V6.

 

They must have the shitty 3.23 rear gear. My 4.8 is strong with the BB tune and a few other goodies. Obviously the 6.2 is a beast, but there isn't much difference in power at all between the 5.3 and 4.8. Even GM rates them within 20 hp stock.

[Zembonez]

The 4.8 is one of the poorest excuses for a truck engine GM has ever produced. Go 5.3 or 6.2 if you need real power. Ever hear someone say they wished their 5.3 powered truck had a 4.8 so it could be anemic, slower, get worse mileage?

 

Don't worry about the 5.3 fuel mileage. It is all related to the right foot. I will drive 80-90MPH all day long and take my 13.5 MPG. Time is money.

 

 

You have to be fWONking kidding me.

 

That's about the stupidest thing you have ever posted here... and that's saying a lot.

[00Silverado4x4]

When I was shopping to replace my Sonoma back in 2006 I knew I wanted the 5.3 but that was ONLY for the towing capacity. I knew I would be towing a bigger trailer eventually and wanted the extra capacity to allow for more trailer options. At the time, the 4.8 was limited to 6400lbs and the 5.3 was 7400lbs. If it wasn't for that I would have gladly taken 4.8.