Originally Posted By: 6starprez
I miss my little '86 Nova CL 5sp. I agree, that engine is as simple as you can get. I used 5W-30 exclusively up until I let it go in 2009 with 235k. I never even thought about putting 20 weight in it since it spec'ed 30 and up.
Actually it recommends 10W-30 or thicker (5W-30 not recommended in warm weather); so, you ran a little thinner than recommended.
Originally Posted By: Astro14
You've run UOA on a 30+ year old engine with mechanical problems and 260,000 miles on it?
There are so many uncontrolled variables here that your UOA don't demonstrate anything. Certainly, a few PPM on one metal in this older, failing engine are not the "final verdict".
The engine consumes very little oil (no top-offs needed between 10,000-mile OCIs) and runs very well. I think it could easily last 1,000,000 miles. It's definitely not failing.
Originally Posted By: Virtus_Probi
Iron went up by 50%, but chromium went down by 62%, so M1 0W40 wins.
EOD
You missed the coolant contamination with the last TGMO 0W-20.
Originally Posted By: kr_bitog
Did you replace PCV valve and piston ring when valve-stem oil seals replaced ?
There is nothing wrong with the PCV valve or rings. The car can drive 12,000 miles/20,000 kilometers without need for oil top-off.
Originally Posted By: Hyrde
It is clear OP is biased towards thinner oils being better, and his analysis of his data reflects that.
I'm not biased. If I was biased, I would stick with only one type of oil. In fact, I ran 15W-40 HDEO for many years in the past.
Originally Posted By: Vlad_the_Russian
I am with the OP. I used Magnatec 0w20 and got 2ppm of iron in 4k miles. Then I used Amalie EURO 5w40 and got 17ppm of iron in 4k miles. Y'all can cry all you want about variables and uncontrolled environment, but these are real life results and you can't just ignore them because it was not done by a lab. Guess what? Your car will spend it's life on the roads, not in the lab. Therefore the testing is valid since it was performed in the real world, real time, real roads. 0w20 wins.
Great to hear.
I will repost the three newest UOAs and post two older UOAs. The 03/24/2013 UOA is TGMO 0W-20 SN and the 6/27/2012 UOA is Pennzoil yellow bottle (PYB) conventional 5W-20 SN. Note that before the Pennzoil 5W-20 SN, I ran 15W-40 HDEO, mostly Mobil Super 1300 15W-40 CJ-4, for about six years. Before that it was 10W-30 conventional, and before that it was 10W-40 conventional.
One interesting trend is that the iron decreased after I switched from PYB 5W-20 to TGMO 0W-20 and kept decreasing until it became stable at 12 ppm. However, it jumped again when I switched to M1 0W-40. This doesn't necessarily mean that PYB was a bad oil. As I said, before PYB, I was running 15W-40 HDEO for six years. It could be that HDEO was causing more valvetrain wear because of less oil flow and the effect carried into the OCI with PYB.
Another thing we cannot rule out is that TGMO 0W-20 SN may have the excellent trinuclear moly antiwear/extreme-pressure additive and lots of it (116 ppm), which may be reducing the valvetrain wear, rather than more oil flow reducing the valvetrain wear.
Regarding sludge being dissolved and giving fake results, this is a fairly well-maintained engine that had three OCIs of TGMO 0W-20 before and I can't believe cleaning effects would alter the wear metals in the oil much.
Regarding the chromium, it's probably being caused by glycol (antifreeze) in the oil. Note that the viscosity of the last TGMO 0W-20 was 9.55 cSt, showing a lot of glycol thickening over the 8.79 cSt of virgin oil. I used the ACDelco cooling-system seal tabs just before I switched to M1 0W-40, which decreased or perhaps eliminated the glycol contamination.
One advantage of M1 0W-40 is its TBN. It can perhaps do longer OCIs thanks to higher TBN, although the difference from TGMO was only about 2 after 5,000 miles.
I was also surprised that the base oil of M1 0W-40 seems to be no better than the base oil of TGMO 0W-20. The two oils have nearly identical TAN after 5,000 miles, indirectly showing similar oxidation.
I have little doubt that TGMO 0W-20 works better than M1 0W-40 in this engine. With the coolant-contamination reduced, I think lead and chromium will both come down in the next OCI. TGMO 0W-20 certainly has less iron wear. This could be because of better oil flow, a higher concentration of trinuclear moly, or cooler-running oil thanks to lower viscosity. In any case, M1 0W-40 doesn't seem to show any benefits over TGMO 0W-20. Last but not least, why waste fuel and sacrifice performance with thicker oil if thinner oil works, in fact works better.