Thin or thick (TGMO 0W-20/M1 0W-40): Final verdict

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This is the ultimate question asked on BITOG. What protects better -- thin or thick oil? Of course, if you say you should follow the recommendation in your owners' manual, you shouldn't be on this site to begin with. There are many folks here who think that they are better off filling their engine with water than with anything thinner than SAE xW-40. On the other hand, there is also the Dr. Haas school, who believe that thin oil protects better because it flows better. So, why is there still no consensus on this? Which is it? To experiment with this, what is better than a simple but very well-built 1980s engine that was built before even multigrade xW-20 existed. In fact, it doesn't even recommend 5W-30 in warm temperatures. 10W-30, 10W-40, 10W-50, 15W-40, 20W-40, and 20W-50 are the recommended grades, with the 10W-xx grades covering the widest temperature range. I was already getting good results with TGMO (Toyota) 0W-20 SN made by ExxonMobil. There was apparently some antifreeze seep problem and I used ACDelco cooling-system seal tabs before the last oil change, which seems to have alleviated the problem. Oil consumption with TGMO 0W-20 SN was small thanks to new valve-stem oil seals -- about 0.3 quarts in 5,000 miles. The last fill was Mobil 1 (M1) 0W-40 SN (older, non-FS formula). Oil consumption stayed the same or perhaps increased slighly to about 0.4 quarts in 5,000 miles. I was surprised that thicker oil didn't improve the consumption -- in fact made it slightly worse. So, TGMO 0W-20 won over M1 0W-40 in the consumption department or perhaps it was a near tie. Sodium (Na) in fact went down thanks to the seal tabs. However, I still have some coolant loss, probably seeping externally. Wear numbers were the real surprise, even though they were something I long feared and suspected about thicker oil. Iron went from 12 ppm to 18 ppm when I switched from TGMO 0W-20 to M1 0W-40 -- a 50% increase in iron wear when switching from thin to thick. With M1 0W-40, all of a sudden nickel (Ni) appeared, which was near nonexistent with TGMO 0W-20. Aluminum, lead, and copper were similar with either oil. Chromium has improved with M1 0W-40 SN, but I attribute that to ACDelco cooling-system seal tabs rather than the oil, as antifreeze (glycol) is known to cause ring wear. TAN was similar with either oil. M1 0W-40 TBN was expectedly higher, as it has a very high starting TBN. ZDDP (phosphorus [P]) levels were similar in either oil. TGMO 0W-20 had a lot more moly (probably the trinuclear type) than M1 0W-40. Fuel economy was a lot better with TGMO 0W-20 than with M1 0W-40. Engine idled somewhat smoother with TGMO 0W-20 than with M1 0W-40 due to less viscous drag. Conclusion: TGMO 0W-20 SN protects better against wear than M1 0W-40 SN. Iron wear is a lot less. This is probably due to better oil flow of thinner 0W-20, which helps more oil to get to critical parts, such as the valvetrain. TGMO may also have some additive advantages over M1, such as higher moly. In fact other grades of M1, such as M1 0W-20 SN, worry me even more as they have very skinny additive packages. Fancier base stocks (PAO and ester in addition to Group III) in M1 may also have contributed to higher wear in comparison to the Group III TGMO, as esters for example are well known to increase wear by competing for the surfaces with the antiwear additives. Less wear and better fuel economy makes TGMO 0W-20 a clear better choice over M1 0W-40. TGMO 0W-20 may be even better for less oil consumption. However, M1 0W-40's higher TBN might help in extended OCIs (over 10,000 miles). Last but not least, not all engines are the same and there may be some engine that really needs thicker oil. I have also lost my trust in European (ACEA) oils after this. Perhaps that BMW would run better with TGMO 0W-20 SN than with ACEA A3/B4 Mobil 1 0W-40 or German Castrol 0W-40. TGMO once again has reinforced my trust. I think we should give Dr. Haas the credit he deserves. Thin wins.
 
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Let's say the iron was from using an ExxonMobil product and Castrol Edge 0w40 wouldn't have done that?
 
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http://www.substech.com/dokuwiki/doku.php?id=effect_of_low_viscosity_oils_on_engine_bearings Of course thick protects better than thin, because with thick you have a greater MOFT which helps prevent wear from metal-to-metal contact. That the main reason why every manufacturer of high performance cars say to run a thicker oil if tracking the car. The oil will get much hotter on the track than in normal street driving, and that could thin it down to a dangerous level. So "thin" can also be created by heating the oil up too much for the intended purpose. I would say most xW-20 motor oils would protect well if used in non-demanding applications (ie, never seeing over 210~220 deg F), but not so much in a harsh use case like track use or heavy towing, etc.
 
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I've done three uoa's so far. RP Synerlec SJ rated 20W50,M1 10W40HM,and GTX 20W50. The 10W40 M1 had slightly higher wear metals than the two 20W50s,with the GTX 20W50 being the best of the bunch. My next uoa will be Pennzoil Platinum HM 10W30. I'm highly anticipating those results to compare to the previous three.
 
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Not very helpful. I did find this. https://bobistheoilguy.com/engine-oil-analysis/ Looks like the main bearings might be a source. I noticed the lead numbers as well. This is an old engine which probably explains these findings. I wonder what the analysis would show with a good 5W-30? That might be the ideal weight.
 
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Originally Posted By: PimTac
Where would nickel come from in an engine?
Maybe a steel alloy or bearing material. Blocks are aluminum. Maybe some exotic aluminum alloy using some nickel?
 
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I don't think Toyota was manufacturing aluminum blocks in 1985. Most likely cast iron block with aluminum heads.
 
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Originally Posted By: PimTac
I don't think Toyota was manufacturing aluminum blocks in 1985. Most likely cast iron block with aluminum heads.
Correct.
Originally Posted By: PimTac
I don't think Toyota was manufacturing aluminum blocks in 1985. Most likely cast iron block with aluminum heads.
Unlikely, as that was older Group IV/V formulations (with esters fighting for the surfaces with antiwear additives) of M1. In addition M1 0W-40 never had that issue.
Originally Posted By: Brybo86
I wish this was done on an engine without coolant loss. Try a different Xw40 next
Coolant loss (sodium) has improved a lot after the ACDelco tabs, which were added just before the M1 0W-40 SN oil change. This seems to show as better chromium (ring wear) numbers and possibly better lead numbers as well.
Originally Posted By: ZeeOSix
http://www.substech.com/dokuwiki/doku.php?id=effect_of_low_viscosity_oils_on_engine_bearings Of course thick protects better than thin, because with thick you have a greater MOFT which helps prevent wear from metal-to-metal contact. That the main reason why every manufacturer of high performance cars say to run a thicker oil if tracking the car. The oil will get much hotter on the track than in normal street driving, and that could thin it down to a dangerous level. So "thin" can also be created by heating the oil up too much for the intended purpose. I would say most xW-20 motor oils would protect well if used in non-demanding applications (ie, never seeing over 210~220 deg F), but not so much in a harsh use case like track use or heavy towing, etc.
Bearing wear (lead) doesn't seem to have improved with 0W-40. Therefore, viscosity of 0W-20 seems sufficient for this application to prevent bearing oil-film breakdown.
Originally Posted By: PimTac
Where would nickel come from in an engine?
This is a very good reference on UOAs: http://machinerylubrication.com/Read/854/oil-analysis-tests Top-end-wear (engines): Characterized by increased levels of Fe (cylinder liner), Al (pistons), and Cr (rings). The presence of Ni usually indicates camshaft/cam follower wear. Nickel (Ni) seems to be coming from the camshaft. I think iron is coming mostly from the camshaft, too. I have sliding, not rolling, rocker arms, which increases camshaft wear. My understanding is that it's hard for the oil to reach the valvetrain, which sits all the way at the top of the engine. 0W-20 is producing a better oil flow than 0W-40 and valvetrain is getting more oil and therefore better lubrication with 0W-20. Since valvetrain works in the boundary lubrication regime (metal-to-metal contact), antiwear/extreme-pressure additives play the most important part and viscosity is not as critical in providing an oil film (as there is hardly an oil film). Better oil flow of 0W-20 seems to lubricate the valvetrain better in this application. Since the viscosity of 0W-20 seems to be sufficient to protect the bearings and it seems to lubricate the valvetrain better, I see no reason to run anything thicker than 0W-20 in this application. Thicker oil is not only increasing wear but also obviously hurting the fuel economy and performance.
 
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Besides cam, the cylinder sleeves I was talking about its steel, most Fe, some Ni, Mo and Cr. Head lubrication will depend on oil pump pressure. Do you have on in spec or not.
 
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Originally Posted By: OPR4H
Besides cam, the cylinder sleeves I was talking about its steel, most Fe, some Ni, Mo and Cr. Head lubrication will depend on oil pump pressure. Do you have on in spec or not.
Everything is stock.
 
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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.
 
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Originally Posted By: Gokhan
Bearing wear (lead) doesn't seem to have improved with 0W-40. Therefore, viscosity of 0W-20 seems sufficient for this application to prevent bearing oil-film breakdown.
Seems a bit inconclusive since the levels for chromium (rings), aluminum (pistons & cam journals) and lead (main & rod bearings) went up in the 0W-20 run dated 9/7/15 compared to the 0W-20 run dated 2/22/14. The 0W-20 run dated 9/7/15 also shows higher in those same metals compared to the 0W-40 run.
 
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flow doesn't lubricate...AEHaas never ever could provide any supportive evidence on flow=lubrication, nor could one of his keenest adherants. As the the test methodology here, there's no back to backs, or even repeat testing, i.e. 0W20, 0W40, 0W20. 0W40, 0W20 to see if the correlations even hold...without a possible (or confirmed) coolant leak...then there's the assumptions on what the metals in the oil actually mean. Pretty conclusive conclusion given the above, eh ?
 
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I'm with Shannow on this. Regardless of whether the test showed 0w40 better or 0w20 better, it's very hard to prove anything with such small sample sizes. Just too many variables. I encourage the OP to make this thread on going. Give us more results and try to stay neutral. One scenario is that they both end up being rather equal and you pick 0w20 for fuel economy. But just one run off each.... give us more. Switch brands if you desire but keep it 0w20 vs 0w40.
 
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