10w-40 vs 20w-50, regarding VII

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Which one of these grades uses more viscosity index improvers? Specifically, I'm talking high mileage oils. The one high mileage 10w-40 UOA here was rock solid, thick 40 weight viscosity after 2700 miles, but most other 10w-40 results shear WAY back into 30 weight territory. How does 20w-50 compare?
 
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Given the VI of modern Group II and II+ base oils, 10w40 and 20w50 are going to have very similar amounts of VI improver, but I suspect the 20w50 is still going to have less than the 10w40.
 
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Good question. All else equal, how much VII would be needed for the major grades? I suspect 5w20, 10w30, 15w40, and 20w50 all would be lower than 5w30 and 10w40. But, all is not equal. I believe companies change additives, additive ratios, and base oil mixes between the various grades in order to get the performance they desire. I do believe 20w50 would need less VII than say 5w30, even though the 20w50 has the greater absolute spread, because the 20 is much thicker from the start.
 

TC

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"Very few manufactures recommend 10W-40 any more, and some threaten to void warranties if it is used. It was not included in this article for that reason. 20W-50 is the same 30 point spread, but because it starts with a heavier base it requires less viscosity index improvers (polymers) to do the job." http://www.vtr.org/maintain/oil-overview.html
 
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quote:
Originally posted by therion: shoot, i just put in 10W-40 MaxLife in my 1997 Jaguar XJ6. When should i dump the oil??? how long before the polymers break down [I dont know]
With modern base oils, 10w40 doesn't require as much VII as it once did. I'd feel perfectly comfortable using a modern 10w40, though I wouldn't use Valvoline just because their oils have shown to be weak in additives and post poor UOAs. (The MaxLife may be an exception, however.)
 

TC

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G-ManII beat me to the punch. That link I posted is at least a few years old. The base oils used since then have improved along with an upgrade to API SL. A 10w-40 of today is probably a significantly improved oil over that weight from 10 years ago. Your oil will do just fine, and I certainly wouldn't worry about it if it's a weight recommended by Jag in your manual (Ya gotta love that phrase, "When in doubt, read the manual..."). If the oil isn't giving you a warm & fuzzy feeling, simply change it out earlier than anticipated, but first use and abuse it for several thousand miles -- you're not gonna burn or shear it substantially in an abbreviated drain. Besides, choosing the thinner option probably ain't bad considering it's Winter right now -- your ride might actually prefer it. [ February 19, 2004, 09:00 PM: Message edited by: TC ]
 
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thanks for the reassurance you guys. I will run this oil at least 2,000 miles before switching over to synthetic blend 15W-40 - hope i don't make any leaks [Razz]
 
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quote:
Originally posted by therion: shoot, i just put in 10W-40 MaxLife in my 1997 Jaguar XJ6. When should i dump the oil??? how long before the polymers break down [I dont know]
I think you will be fine. I now have 2000 miles on the 10w40 Maxlife in my '95 Ford 4.9L pickup and the oil pressure has been steady right along. I would think if the polymers sheered much and viscosity dropped, it would show in lower oil pressure (5w30 gave me 20% lower oil pressure). Also, Maxlife is supposed to have a lot of detergents, so I'd expect it to do some engine cleaning.
 
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quote:
Originally posted by TallPaul:
quote:
Originally posted by therion: shoot, i just put in 10W-40 MaxLife in my 1997 Jaguar XJ6. When should i dump the oil??? how long before the polymers break down [I dont know]
I think you will be fine. I now have 2000 miles on the 10w40 Maxlife in my '95 Ford 4.9L pickup and the oil pressure has been steady right along. I would think if the polymers sheered much and viscosity dropped, it would show in lower oil pressure (5w30 gave me 20% lower oil pressure). Also, Maxlife is supposed to have a lot of detergents, so I'd expect it to do some engine cleaning.

K, cool. I put MaxLife becuase I just bought the car and I wanted to cleanse the engine alittle bit before putting 15W-40 Sem-Synthetic
 

TC

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Easy enough to quantify that with a few examples. As you may know, Total Base Number "TBN" indicates long-term ability to control acids, reflecting detergent/dispersant qualities, with higher numbers better: Kendall, Union 76: 6.2 TBN Valvoline All Climate: 7.0 Chevron/Havoline: 7.4 Valvoline MaxLife: 8.0 Shell Rotella: 11.5
 
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quote:
Originally posted by TC: Easy enough to quantify that with a few examples. As you may know, Total Base Number "TBN" indicates long-term ability to control acids, reflecting detergent/dispersant qualities, with higher numbers better: Kendall, Union 76: 6.2 TBN Valvoline All Climate: 7.0 Chevron/Havoline: 7.4 Valvoline MaxLife: 8.0 Shell Rotella: 11.5
Nice [Smile] I like the MaxLife numbers. Any chance on getting numbers on how shear stable it is?
 
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quote:
Originally posted by therion: I like the MaxLife numbers. Any chance on getting numbers on how shear stable it is?
I called them the other day about that. The 10w40 has a minimum HT/HS of 3.5. The 10w30 was 3.3, but not sure if that was minimum or average. Wish I had gotten the other grades too. Also note the nice flash point on Maxlife 10w40 (listed as 242C). Pour point pretty decent too at -36C.
 
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The following w.r.t. dino oils only: "The higher the VI, the more multigraded the oil" (How to read a can of oil (Part 1), by John S. Evans B.Sc., WearCheck Africa)/. Here are some oils (Chevron Supreme, Exxon Superflow, and Citgo Superguard) ordered by their VIs: 159 5w30 Chevron 158 5w30 Exxon 154 5w20 Citgo 154 5w30 Citgo 153 5w20 Exxon 148 5w20 Chevron 148 10w40 Chevron 148 10w40 Citgo 147 10w40 Exxon 137 10w30 Citgo 135 10w30 Chevron 135 10w30 Exxon 125 20w50 Exxon 122 20w50 Chevron 121 20w50 Citgo The blank lines are there to emphasize the bigger drops in VI as you go down the table. It is clear that the 5w30 is the most multigraded of these various grades, with the 5w20s following a close second. The 10w40w follow close behind the 5w20s. Then there is a big gap to the much less multigraded 10w30 and another big gap from that to the 20w50. The very little data I have on 15w40 suggests it would follow close with the 10w30s or be somewhere between 10w30 and 20w50. If the viscosity index improver additive levels are roughly comparable to the VI (I know part of that is the natural VI of the base oil, but all else equal...), then 10w30 is the way to go except when extreme cold dictates a thinner oil. The idea of running 5w30 or 5w20 during hot summer weather appears absurd from this viewpoint. And the much maligned 10w40 ("too much viscosity spread," "suffers permanent viscosity collapse," etc.) appears actually to be more stable than the ever popular 5w oils. Anyway, the quote from John Evans' article got me to thinking about this again. It seems a simple way to look at the viscosity index improver question. Even when you look at each of the three brands above separately (removes some, but not all, the unknowns) each separate brand still gives the same relationship I have described above. Maybe we can add data on a few more brands and see how the order holds up. I purposefully avoided synthetic blends to minimize the unknown variable. Valvoline Durablend, for example, would skew the results because it has higher VIs due to its synthetic fraction. [ February 27, 2004, 01:58 AM: Message edited by: TallPaul ]
 
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