Not allowed to run full synthetic I guess..

[4xcrazy]

So a month or so back, the Avalanche, with the freshly rebuilt 5.3, well, about 24k ago now anyways, decided to develop a lifter type noise tick at start-ups first thing in the morning, or after it had been sitting for some time.

Was running a full synthetic 10/40 Mobile 1 oil, with a Mobile 1 oil filter.

Just out of curiosity, I switched to Castrol high mileage 20/50wt, non synthetic, still using a Mobil 1 filter, new of course.

noise went away completely.

Pretty well bet the thicker oil had something to do with it, but where I used to buy the Mobile 1 in 10/40wt, or any place that I have seen locally so far, doesn't have a full synthetic in anything thicker than 10/40, and that's only at WalMart.

I have yet to see anything thicker than 10/30 at a local auto parts store.

Guessing something with one of the lifters.

Kind of annoying, I like this 5.3, but this particular one seems to be a problematic unit. As some may remember, this is the one that had the failed roller lifter and cam issue that prompted me to just have the entire engine rebuilt to avoid any metal contamination a year so so back.

Engine only had 133 k or so on it when this happened.

Thoughts/ideas?

 

[diesel4me]

Your oil filter have an anti-drainback valve?...a good one like Wix or AC should...though the filter probably stands thread side up and cant drain back,it might make a difference..a little air getting in the oiling passages can take awhile to get bled out..

I haven't used synthetic in anything I own--for one,they are all too old,and been run on who knows what before I got them,any wear is already done-and I dont want to risk loosening up any crud and doing more harm than good...

The thicker oil might have helped,and I think non synthetics have more viscosity than synthetics..Mobil 1 20w50 pours like water compared to 20w50 non synthetic ..the extra viscosity might increase your oil pressure a bit,and cushion any slop between parts better than synthetic..

I have seen a few later chevy V8's that were replaced after the owners said they "blew up" after overheating,or just started knocking from letting the oil get too low...both had a lifter that was a bit sloppy in the bore in the block...
I wonder if synthetic is so "slippery" and thin,it lets a lifter flop around in its bore,while thicker regular oil might cushion it enough to keep it quiet?..

 

[rob h]

Noisy at start up is about usual with the ls motors, especially the 5.3 and 6.0. If it was me wouldn't run any heavier than 10w30. Id imagine on cold mornings the oil pump doesn't like the 20-50. A lot of times there is carbon build up and id use a top engine/injector cleaner in the gas. Run a few tanks of good gas thru it. Mine has 120,000 on it and has only seen 5w30 synthetic mobil 1 and about 30,000 miles ago I started using ams oil signature oil. The only time theres any noise is when its real cold out, it goes away pretty quick when it gets a little heat in it. Also try using a wix filter for your next oil change.

 

[rebelgregory]

The dreaded piston slap? I had an 01 1500HD 6.0L with a real bad case of the slaps. Never affected performance though.

 

[4xcrazy]

No, this was definitely a lifter tap. Had too many previous and including my burb having that noise. Kind of wondering on the brand of lifter the shop used I had the engine rebuilt at, it was the same place the Burbs engine was done at.

Either way, it hasn't seemed to make the engine run any different, maybe quieter all around, I'm very meticulous when it comes to oil changes, so I really don't see why the engine shouldn't last a nice decent long time

 

[Stomis]

Valvoline make 20w50nsynthetic "racing" oil I believe.

 

[Fordum]

Amsoil makes at least two 20W50s. I use the regular one.

 

[dhcomp]

What is recommended for that motor from GM? I think its 5/30 or 10/30.

20/50 sounds really heavy for that motor. Yes, it will be quieter, but what will you overstrain?

I'd stick closer to the stock oils.

 

[clandr1]

What is recommended for that motor from GM? I think its 5/30 or 10/30.

20/50 sounds really heavy for that motor. Yes, it will be quieter, but what will you overstrain?

I'd stick closer to the stock oils.

GM spec calls for 5w30, and I agree - I wouldn't go heavier than 10/30 (and even then, only during the summer).

Even with 5w in my '05 5.3L, the oil pressure gets pretty high under accelleration during cold mornings before my motor really warms up. I'd hate to think what kind of stress 10w or 20w would put on it in those same conditions.

I have run Mobil 1 high mileage 5w30 religiously since my truck hit approx 75k miles.