AC Delco SN 5w-30, 3k, GM 2.4L GDI

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223
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Iowa City
My latest UOA for my GM 2.4L Ecotec with GDI. History of fuel dilution per Polaris. The comments are 60 seconds worth canned statements as usual. NL = New Lube reference, AC Delco 5w-30 Full Synthetic API SN Sample 1 is Amsoil 5w-30, only 1530 miles due to timing chain and HP Fuel pump replacement. Warranty work. Sample 2 is AC Delco 5w-30, dealer installed after ring/piston replacement under warranty. New timing chains, head/valve work completed. Iron and silicon high due to break-in and new gaskets. Changed early to remove wear contaminants and fuel concerns. Sample 3 is AC Delco, dealer installed, sample after 15 minutes to gauge amount of Short Volume Oil Change (SVOC) mixing and PC. Retained 5ppm of iron, 1ppm aluminum, and 8ppm sodium. Large amounts of 4um particulates remained. Amsoil FF Filter cleaned up the larger particulates. Viscosity and TBN already starting to drop, probably from 10-15% old oil. Polaris wont test used engine oil for particulates. Sample 4 is same fluid as 3. Close to normal iron and other wear metal accumulation, minus old oil mixing. Viscosity stabilized at 9 (25w), and TBN dropped by 2.4. TBN drops quickly at first and then should level off. Moderate increase in Oxidation and Nittration. Boron drops to 60% reserve. Silicon seems to have stop leaching, minor amount of sodium. Same fuel dilution. Piston/and rings are nearly seated, and cams and chains settled in. No more chain noise. Sample 5 is same fluid as 3. Iron rate is slightly lower, all other metals stable or no change. Sodium accumulation is down Viscosity still at 9, TBN is lower but not dropping as quickly at 2.7, actual TBN is 4-5. Slight increase in Oxidation and Nirtration. Boron is at 40% looks like is pulling double duty, EP/AW and to help with fuel dilution. All additive metals are stable. I expect some decrease, but little change. Fuel dilution is down slightly, no major contamination. Rings/pistions fully seated, compression is 250-250psi in all cylinders. Long Term Fuel trims are at or close to 0. Oil Consumption is near 0, and little blow-by in PCV system. I am considering switching back to Amsoil SS 5w-30 or 0w-40 SN Plus. It gets down to -20 in the winter, outside parking and the higher viscosity will help with the unavoidable fuel dilution with GDI. The 0w-40 has a slightly higher Noack, lower the better for GDI and valves. I don't race the engine, and the VVT and crank/cam clearances should be able to handle the 40w viscosity for a short while. Let me know what you think. My goal is longer OCIs, preferably one year and 8-10K.
 

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2,900
Location
High Tax Illinois
Why would you what to go a year with a known fuel dilution GDI engine??? With all the money being spent on samples why not just change it every 6 months??? I had a '12 Nox, it got oil changed 2000 miles or 3 months and even then the oil would come out looking like coffee smelling like gas.
 

Talent_Keyhole

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223
Location
Iowa City
Originally Posted by oldhp
Why would you what to go a year with a known fuel dilution GDI engine??? With all the money being spent on samples why not just change it every 6 months??? I had a '12 Nox, it got oil changed 2000 miles or 3 months and even then the oil would come out looking like coffee smelling like gas.
The extra oil samples was to check condition of the engine when I bought the car at the beginning and after the major work. Fuel smell is hardly noticeable any more and my catch can is virtually clean. Fuel does collect in it, but it evaporates and consumed in the engine. It is like a crankcase EVAP system The inside of the engine, camshaft covers and oil pan were heavily varnish and build-up from years of cheap oil, and use of the OLM, which was poorly programmed. Excessive blow-by adds to the fuel contamination.
 

Talent_Keyhole

Thread starter
Messages
223
Location
Iowa City
Originally Posted by Triple_Se7en
Your goal should be 5K OCIs.
That is part of my goal. Will probably sample at 2500 and again at 5000, and see how it looks with 0w-40
 
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