1997 GMC Sierra 350 Castrol GTX BIG IMPROVEMENT!!!

[Chris B.]

Hello guys,
This is the 2nd UOA from my GMC Sierra. Here is the history of it as far as I know. I bought this truck in March 2011 from the original owner. It only had 75,000 on it and it is mint inside and out and was garaged all the time. The original owner only put 1,900 miles on it per year over the past 10 years so it sat a lot. When I bought it the intake manafold was leaking badly and I had my mechanic replace it and tune it up and replace all fluids, truck is 100% now and runs well.
After the intake gasket repair I drove it home and did another oil change with Castrol GTX 5w30 and also added Auto RX to help clean up things a bit not knowing how dirty it might be inside as the original owner did not have any maintenance records and the oil when I bought it looked DIRTY and black and was low on the dip stick but still in the safe zone.
Wear dropped a lot in this sample compaired to the 1st sample. I only drive this truck a couple times a month when I need a truck so it sits for a couple/few weeks at a time in my garage. It took me 14 months to get the 3,000 miles on this sample. I had a 1997 Tahoe with the same engine and I always used Castrol GTX and Blackstone stated it was the lowest wearing 350 V8 they had on file. Here is the details on the oil sample:

*82,185 miles on engine/truck
*3,000 miles on oil
*Oil in use from 79,164 to 82,185 miles and from 2/2012 to 4/2013.
*Castrol GTX 5w30 and is an Auto Rx flush cycle.
*Napa Gold oil filter.
*Napa Gold air filter is new.
*1st UOA 15oz of oil burned and this UOA 0 oil was burned or added.

1st number is 1st UOA and the 2nd number is this UOA. Both UOA's have 3,000 miles on them:

ALUMINUM 3/4
CHROMIUM 1/1
IRON 22/10
COPPER 104/51
LEAD 24/13
TIN 0/5
MOLYBDENUM 2/3
NICKEL 2/1
MANGANESE 1/1
SILVER 0/0
TITANIUM 1/0
POTASSIUM 44/34
BORON 8/7
SILICON 79/61
SODIUM 274/342
CALCIUM 1515/1784
MAGNESIUM 10/9
PHOSPHORUS 640/703
ZINC 686/843
BARIUM 0/0

SUS Viscosity @ 210 F 56.3/56.1
cSt viscosity @ 100 C 9.16/9.10
Flashpoint 415 F/420
Fuel 0.5
Antifreeze POS/POS
Water 0/0
Insolubles 0.3/0.3
TBN 4.2/2.9

I'm a little worried the intake may be leaking a little coolent in the oil still. What do you guys think? Also thinking Silicon is still high because of the intake repair and the gasket it still leaching into the oil a bit? What do you guys think of this sample and how is compairs to the 1st UOA? Think the engine is doing well and settling down? I just hope it is solid and will last me a long time! Thanks for any input! Picture of truck:

 

[BPman]

Thanks for posting some great pics of your truck and the matching big rig.
Castrol GTX 5/30 is a very good part synthetic, but it might be worth asking your dealer what he uses or taking a look at the oil finder listings for your exact engine.
Unfortunately you might be right about the coolant intrusion as GTX does not contain Potassium (It does have Sodium) in the UK and I suspect it is the same in the US. The top end figures (Iron, Alum and Chrome) look good, although if your oil lab does not have some averages that is difficult to figure out.
I'm sorry to say that the Lead figure of 13 ppm in 3,000 miles might be interesting, the Copper is another high one that could be from oil cooler chemistry, but also looks interesting. It's difficult to say much else until the potential coolant to oil system leak is investigated and I would do that asap.

Good luck and I hope to see your next UOA with some lower Pb, Cu and K. I love the YOKO white lettered tyres!

 

[volk06]

Originally Posted By: BPman
Thanks for posting some great pics of your truck and the matching big rig.
Castrol GTX 5/30 is a very good part synthetic, but it might be worth asking your dealer what he uses or taking a look at the oil finder listings for your exact engine.
Unfortunately you might be right about the coolant intrusion as GTX does not contain Potassium (It does have Sodium) in the UK and I suspect it is the same in the US. The top end figures (Iron, Alum and Chrome) look good, although if your oil lab does not have some averages that is difficult to figure out.
I'm sorry to say that the Lead figure of 13 ppm in 3,000 miles might be interesting, the Copper is another high one that could be from oil cooler chemistry, but also looks interesting. It's difficult to say much else until the potential coolant to oil system leak is investigated and I would do that asap.

Good luck and I hope to see your next UOA with some lower Pb, Cu and K. I love the YOKO white lettered tyres!


Thats not correct for the US, GTX is conventional oil here. The GTX high mileage is a syn blend.

 

[jorton]

You should take a sample from the current oil change at 1500 miles and get it tested for coolant. Hopefully POTASSIUM will be down 10 or 20 points more.

 

[bullwinkle]

Keep doing fairly short OCIs & getting it up to operating temperature regularly, looks like you're getting the coolant out. Is your coolant level staying full, and how does the inside of the oil fill cap look? If you don't have the telltale white mucus-like spooge on the inside of the cap, and the antifreeze is staying full, it should get better gradually.

 

[bullwinkle]

And 5W30 is the correct (original) viscosity oil, and there is no oil cooler.

 

[Chris B.]

The underside of the oil fill cap is always spotless. Once in a great while I have to add a tiny bit of coolent to the tank to keep it at the full line. Maybe an oz. or 2 in a year. I was thinking it was evaporating?

 

[BPman]

Originally Posted By: volk06
Originally Posted By: BPman
Thanks for posting some great pics of your truck and the matching big rig.
Castrol GTX 5/30 is a very good part synthetic, but it might be worth asking your dealer what he uses or taking a look at the oil finder listings for your exact engine.
Unfortunately you might be right about the coolant intrusion as GTX does not contain Potassium (It does have Sodium) in the UK and I suspect it is the same in the US. The top end figures (Iron, Alum and Chrome) look good, although if your oil lab does not have some averages that is difficult to figure out.
I'm sorry to say that the Lead figure of 13 ppm in 3,000 miles might be interesting, the Copper is another high one that could be from oil cooler chemistry, but also looks interesting. It's difficult to say much else until the potential coolant to oil system leak is investigated and I would do that asap.

Good luck and I hope to see your next UOA with some lower Pb, Cu and K. I love the YOKO white lettered tyres!


Thats not correct for the US, GTX is conventional oil here. The GTX high mileage is a syn blend.


The Castrol GTX EU class ratings should match the US ones, BUT we don't have GTX HM series available apart from the 10/40 HM which is only sold in Germany and France.
GTX 10 or 15/40: Conventional
GTX 5/30 (Very popular): Part synthetic, BUT this might be called synthetic blend in the US.
The other GTX oils like the 10/60 are only sold in the US.

 

[BPman]

Originally Posted By: bullwinkle
And 5W30 is the correct (original) viscosity oil, and there is no oil cooler.


OH! If there is no oil cooler with Copper pipes the Cu figure seems to be rather more significant.

If the coolant to oil leak is not fixable within budget, then I would never, ever use anti freeze during the summer if possible. The water boils off but the AF just wrecks the detergents and is ten to twenty times more damaging than water. Distilled water, a can of stop leak and some marine shop soluble oil will help.
Some blue (Plum) veggie dye will help confirm a slow leak sometimes, as blue and oil yellow gives dark green oil, but my methods are rather odd sometimes. Only one half teaspoon for Blue dye or you will always have blue coolant even after fixing the head gasket or bolts etc. Don't drop the other half spoonful in the swimming pool as it's enough to cause a real problem. Your visitors will have the Blues!

If the HG is beyond budget repair then I would try Maxlife 10/40 and a can of top quality stop leak (LM in the EU), in addition to switching to water and stop leak for coolant. If the OP can keep the revs low and not boot it around town, then once the head bolts are checked it might just stop the leak. 60/40 in favour of it stopping assuming the head bolts were tightened correctly AND the engine has not been over heated by the previous owner.

 

[Chris B.]

So you think the potassium and silicon is still left over from the intake manifold repair 6,000 miles ago? Lead was almost [censored] in half and iron was more then cut in half. Copper dropped big time too but aluminum went up a little.

Think I have a problem or is it settling down. Wish I drove it more to get faster results/

 

[Clevy]

Originally Posted By: Chris B.
So you think the potassium and silicon is still left over from the intake manifold repair 6,000 miles ago? Lead was almost [censored] in half and iron was more then cut in half. Copper dropped big time too but aluminum went up a little.

Think I have a problem or is it settling down. Wish I drove it more to get faster results/


Don't listen to this guy. Look at his posts. He keeps backtracking because he doesn't know anything about the vehicle,nor the oil.
If you are really concerned pm Dnewton. He has a ton of data and your engine is either a 305(5.0)or a 350(5.7)
The 5.3 was never installed in that body style. They first went into a silverado in 1999