OCI GC question

[CONMCK]

My OCI light just came on with 5600km (3400miles) on this oil. Looking for opinions on how much further I should go before changing the oil. Previous UOA below. As you can see the last change i went 1940km (1200miles) beyond the OCI light and I believe I could have still gone further and been okay. Previous has no TBN #'s, I will have the TBN/oxid/nitr done on the next one.

2001 GMC sierra 1/2 ton ECSB 4X4 auto 5.3L 4.10 gear. UPD intake, westers power programmer, 305hp @ 5600 rpm. All oil filters used were AC PF-59C never any top up oil added. QS-quaker state synthetic, RP-royal purple synthetic, GC-german castol. The most recent OCI the oil/truck was worked very hard pulling a 7000lbs holiday trailer. The change oil light actually displayed at approx 4400km, and I extended the change until 6340km. All previous changes were completed as soon as the OCI came on.

Oil.....QS.....QS.....RP.....RP.....RP.....GC........GC
VIS...5w30..5w30..5w30..5w30.5w30..0w30...0W30
Date..03/02.03/06.03/08..03/12.04/04.04/08..04/11
KM,oil.5916..7507..6495..6282...5675...6760...6340
km
truck..26241.33748.40243.46525.52200.58960.65300

si.......27......13......55......43......34......15......10
fe.......18......30......17......29......10......10......11
pb.......12......12......8.......8........6.......6........4
cu.......65......51......96.....114....111....60......42
tin.......1........2.......0.......2.......1........3........2
al........3........5.......3.......2.......1........3........4
ni........1........1.......0.......0.......0........0........0.
ag.......0........0.......1.......1.......1........0........0
boron...5........24.....0.......0.......0.........1.......1
phos...752....768....841...822...1160...804.......750
zinc....914....868...1030...998...982...1020......937
calc...2360..1830..2250..2110..2040..3180......2990
magne...23.....25.....84.....15.....8......138.......140
moly....26.....27.....120....135....128....15........5
antim...2......2.......1.......1.......1........2.........0
lith......1......1.......2.......1.......1........0.........0
Vis 40
cSt....59.0..56.2.*61.8*.55.0..53.8...66.1.....71.0
100cSt.10.3.9.63.*10.0*.9.32.9.16.11.37.....11.9
fuel......N.....1.2...N.......1.5....N......N..........N


All samples contained no water, sodium, titanium, barium, or glycol. Copper is high which seems typical for the LS-1 engines.

I'm not sure what to make of the high silicon numbers.

 

[TooSlick]

I believe 71.9 SUS is > 11.9 Centistokes (?), so this sample does show some thickening in this application. You should be able to run at least 10,000 km with this engine/oil combo.

TS