I have a 02 GMC Z71 that I bought new and has 40K miles on it. I seldom drive the truck because I have a company car and it has always been garage kept and well cared for. It has had the knock noise that many trucks have had that were made about the same time and according to the dealer they claimed that it was the ring design that caused this noise and it was common and nothing to worry about. The truck has used a qaurt of oil every 2K miles since new and is pretty noisey when it is first fired up. The first 2 oil changes I used GM Goodwrench oil then switched to Mobil 1. I run 5W30 in the winter and 10W30 in the summer. The 5.3 is extremely sensitive to oil filters. It is much more noisey on start up with any filter other than a AC filter. I was thinking of going to a thicker oil to try to reduce the oil comsuption and possibly quiet the motor down some. I have raced turbo Buicks for years and 15W40 Rotella oil is common with them and has proven to be one of the best choices and I know a few Outlaw 10.5 racers (one that uses Rotella in a 2K+ horspower Nelson 427 LSX motor with twin 88's)that swear by Rotella so I was thinking of going that direction. This truck sees zero abuse other than pulling a 5K pound trailer occasionally and it usually tows less than 2K miles a year. Thanks for the advice.

Steve

 

the noise you are probably hearing is piston slap. does it go away once the truck warms up? if so then theres nothing you can do about it. but i wouldnt switch to that thick of an oil in a engine that was designed for 5w-30

 

yeah, I wouldn't be concerned with start-up noise. Many of us, including me, get the noise without any ill effects.

 

In my 00 silverado I switched to Valvoline High mileage motor oil.
I went with 10-30. After 2-3 oil changes it stopped burning oil and the valvetrain finally quieted down. Before I switched, With Around 80k on the clock, I was burning 1 quart of oil almost every 2k miles. I always changed my oil around 2500-3000 miles prior to this. I now have 122K on the clock and I even put it on a wheel dyno at 119k. BTW it put down 240hp to the wheels and I think around 260TQ Its BONE STOCK too!!!

I also beat the living **** out of it from time to time. I think in the new motor I am going to try Castrol motor oil.

 

The noise you hear is piston slap. This is caused by the short piston skirt that LS motors have. Even some lt1's have this same noise. its pretty normal on start up, some cars are different than others. but if the truck is using up that much oil in a regular oil change, there is a problem somewhere internally in that engine.

 

Ya it was burning that much oil before I switched. Since I switched, It no longer consumes oil. The valve train Noise in my engine has to do with the lifters not pumping up properly. It was and upper end noise and never went away at any RPM or at any temprature. After switching It went away after 2-3 oil changes. Piston slap is an intirley different Noise and Is Still presnet on start up and has been since I have owned it.

 

I've heard of guys using german castrol 0w30 to quiet down these motors, never tried it though. I use mobil1 10w30 and I am just used to the noise now until its warm. Almost all of these motors are noisy especially a cammed one.

 

Another option is Castrol 10W60,


a synthetic blend, It's really good in these engines.

 

mobile 1 15w50 is wat i use in my gto and it made the sewing machine type noise alot quieter

 

I was told to use 15w50 in my forged 402.

 

i run 10w 30 in my forged 383, but it gets changed depending on the number of passes, so the oil never sees more than 1000 miles.

try a thicker oil like these guys are suggesting. it may solve some of your problems.

 

Your observations seem to fit with my experience. My A4 (78,000 mi) car has used a quart every 2000 miles since I have owned it and I don't consider it a big deal. I've mostly used Castrol GC 0-30. As far as I can determine, it has cold piston slap that's gotten worse over time.

My M6 (84,000 mi) car uses no oil, but is very noisy and it doesn't go away until the engine has been fully warmed up for about 10 minutes. I've noticed, though, that if I let it idle on start up for a minute, it's much less noisy when I pull away. Over the past several months, the A4 car has started to develop the same noise, though it goes away much quicker.

Like you, I believe this noise is from the lifters not fully pumping up. I thinking idling it for a minute helps them pump up and that's why it's not as noisy. But its pretty hard sometimes for me to distinguish between top-end noise and piston slap.

 

I just got done changing the oil in my car a few minutes ago. Added the 15w50 mobil 1 as directed and she sounds a lot more calm under the hood. Valvetrain noise is reduced is what I am talking about. The break in oil looked like water coming out. Black water. BTW she feels so much stronger in this cool Michigan air that is being rammed/sucked in thru the VaraRam. I probably should check the filter and clean it to see if she's got anything left. LOL. God I can't wait until UPS gets here with the tires and rims I had to leave at LGM

Anyways just thought I'd post up and suggest a thicker oil.

 

I know Louis wouldn't give bad advice because he is "creme de la creme" but I always thought/been told the thicker oil would not drain back into the pan fast enough on these motors......Maybe just another myth.......Did he drill out your lifter trays?

 

I asked and re asked, and was told yes run the 15w50. After changing the oil the psi was up a few and stayed up a few even after coming up to operating temps. The noisy valvetrain was a little more quiet too.

You'll have to ask Louis if he drilled them out. I have no idea.

 

As long as I let it warm up for at leat 5-10 minutes I don't hear the piston slap under load when I leave in the morning. If I jump in and try and leave right away it sounds like Midget with a hammer for about 30 seconds then goes away. In 03 Gm started to add the anti friction coating to the skirts to reduce the noise issue on start up and ad in better wear. I just got rid of an 03 engine that had around 60k on the clock and it still looked new inside.

 

I run a conventional 20w50 now. It quieted down the piston slap and doesn't burn nearly as much oil as it used to....But it still has the sewing machine noise(big cam though).

 

That noise is normal, so I would continue to run 5w30, as recommended by GM. Neither my 4.8 or 6.0 has burned any oil though. I would be concerned about 1 qt burning every 2k mile as I said, my 4.8 had 143k on it and didn't burn anything.