It is a two-wheel-drive model -- a 1500 LS. It has the extended cab, 5.3L V8, 3.73:1 rear axle and the Z85 package. 120,000 miles on it now.

 

I have a 99 Silverado with a 5.3. It's a 4 wheel drive 1500 with extended cab and 8' box. It's about 300 miles short of 230,000 and uses maybe most of a quart between oil changes which I don't feel is too bad. It starts at -20 degrees here in MN. It also has one bolt broken on each exhaust manifold. The mechanic told me that they've been broken for a long time so I'm not going to do anything with them. Once the manifolds warm up the "tick tick tick" noise goes away. I took it to FL in April and got in the high 15 mpg pulling a trailer. One tank got just over 16 mpg but we probably were going downhill with a tailwind that tank full. It still runs great and is a keeper.

 

It is likely piston skirt slap. If it goes away in about 20-30 seconds, likely that's it. A common problem with the 5.3. Mine has been doing it for about 150,000 km, and I'm at 348,000 and still going strong. I'm curious though, why many of you get such terrible mileage. I get 30 on the highway and 24 in town.

 

That's probably because your mileage is in kilometers with Imperial gallons. LOL!

 

I've been driving my "99" Z71 with the 5.3L w/3.73 gears since I bought it new and have seen no decline in performance or fuel mileage (15-18mpg) running Firestone Destination MT 285's since 3000 miles on it ( I now have 180,000). Uses no oil, I had the tranny rebuilt at about 145,000 miles ( heard that that seems to be the normal mileage for these trannies, my sis has a 2001 5.3L silverado 2whd and put a new tranny in at 148,000 and she has 235,000 on it with no other issues)
I ran castrol syntec in it till I moved up to North Dakota 5 years ago and then I switched over to full synthetic. She starts at -40 with no problem.
She has taken me over some of the highest passes in the Rockies and through some major floods down south all without so much as a hiccup. Plan on driving her into the ground before I get another bow-tie.

 

I have a 2002 240,000 still runs great gets around 16/17 miles to gal change oil and filter every 3000 new plugs and hoses and a new fuel pump around 150000 this is a Z71 used to pull boats, tractors and what ever else I need great truck

 

The LS engines (4.8, 5.3, 5.7, 6.0, 6.2) are all the same engines with different stroke and piston sizes. These engines are all great perform well and hold up quite well. They often will smoke at startup (just a little puff) which uses a tiny bit of oil between changes but it isn't anything to worry about. By the way the 5.7 from 1997-98 on are actually only 346 cid not a 350cid ... Just read up about LSx motors ... They are all basically the same engines no matter what size.

 

24/30 kmpg and 12/20 MILES per gallon is basically the same thing ....

 

I have a 2010 Chev Silverado Z71 5.3l V8, well maintained on a regular basis at the dealership I got it from. 5 years later and now she leaks oil like a beached tanker and the Stabilitrak Service light is annoying as hell when there are no problems with the truck besides the now leaking oil which the dealership can not fix now after many shop visits. Apparently its "Engine Block Porosity" laymans terms, the engine shrunk over time.
On the other hand, my 1997 GMC Sierra 5.7l V8 with 300,000 plus kilometers on it runs like a mint still. No oil leaks, hardly uses oil , great gas mileage. And she still has power and can beat most Hemis and newer trucks from the green light.
Im looking for another 1997 GMC, any model.

 

Thanks all!! I now have 82K miles on my 1999 5.3L Silverado and she runs wonderfully. Here are the service items I've completed to keep her running for many years. Dropped the tranny pan to replace the gasket, filter and synthetic ATF. Replaced the fuel filter. I now change the oil with Mobil 1 5W30 EP and Napa Gold filter every 5K miles. Installed new AC Delco plugs and wires. Flushed the radiator with new Dex Cool fluid. New Autozone brake pads and rotors. New e-brake shoes. Drained the rear diff fluid and replaced with fresh Penzoil 75/90 and one of my axle gaskets/seals was leaking so those were replaced with a new set National gasket/seals. Spent an hour cleaning the throttle body, so that clean air was being pulled into my 5.3L! Installed a new thermostat. Cleaned the MAF sensor. For fun and since this is a single cab and use for fun I added a few electronics....alarm, remote start, navigation system, replaced all the speakers and 10" sub to crank my country music. Installed a Linex premium bedliner.

Any other items in the motor that I should service?