10w-40 Gets A Bad Rap!

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I realize this has been discussed before, but I continue to see the myth perpetuated. The criticism of dino oil of this grade has been based on the viscosity "spread" and therefore the ASSUMED high amount of VII used. I believe looking at the viscosity index number is the most accurate way to determine the amount of VII used; as long as your aware of which base oil is used and its' VI. Usually the same group base stock is used for 5w-30, 10w-30 and 10w-40(based on CAS#s). The viscosity indexs average 140, 150 and 160 respectively(for most brands). So if anything 5w-30 should be the most maligned, NOT 10w-40! [Eek!] BUT, with the quality of todays VIIs I don't believe either of these grades would pose a problem for 99% of drivers. * With all the bad press, someone just joining the forum would be under the impression 10w-40 was EVIL and should be avoided(I know I was). So, I think we need to be a little more clear. [Smile] Steve
 
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quote:
Originally posted by 69 Riv GS: BUT, with the quality of todays VIIs I don't believe either of these grades would pose a problem for 99% of drivers.
BUT, you must realize that BiTOG is composed from a small cross-section of that other 1%! [Big Grin] Define problem though: Do you mean part failure due to engine lubrication? Or do you mean oil consumption because the ring pack is clogged up with the remanants of VII's? Or do you mean seals that no longer function properly because the owner used an inferior lube? Seriously, I'm starting to come around and really don't have a problem with modern 5w-30's and 10w-40's given that the OCI isn't too long...4,000 miles max! Matter of fact, I'm gonna use Pennzoil High-Mileage 10w-40 on my next oil change!
 
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I like 10w40! It beats 10w30 on HT/HS and flash point (hopefully NOACK too) and still cold cranks almost as good as a 10w30. I suspect the companies use better base oil in the wider spreads. For example, look at Valvoline Durablend MSDS info for three grades: 10w30 is 23-33 % hydrotreat/ 51-60% solvent dewax 10w40 is 74-84 % hydrotreat 15w40 is 23-33 % hydrotreat/ 51-61% solvent dewax I am currently running the 15w40, but had I known this I would have gotten the 10w40, looks like a much better oil. It would be interesting to research the other brands for this effect. EDIT: Oh yeah, 10w40 gets you out of the API starburst thing too. [ July 16, 2004, 09:08 PM: Message edited by: TallPaul ]
 
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quote:
Originally posted by TallPaul: EDIT: Oh yeah, 10w40 gets you out of the API starburst thing too.
The starburst symbol is the ISLAC EC designation . API SL oils had the Phosforus capped at 1000 ppm max which effectively capped the zinc . Thing is , most oil companies went ahead and used the same additive pack in the 10w-40's as the lower VI oils they make . I suppose it was easier and less costly to do so but they could have loaded the 40wt up with zinc had certain companies chose to and of note , Castrol did with their Syntec 10w-40 [Cool] Paul , I believe if you were to check into the 5w-30 wts you would find most all of them use more group II than the 10w-30 wt brother in the same line-up . This does not mean a 5w-30 will be entirely comprised of group II though . My opinion is they do this for superior cold and hot performance and can do so with the same amount of VII's so as to stock but one additive pack for their entire PCMO line-up. I have seen in the question of the day section that modern and better VII's play more roles in a formulation than merely increasing the viscosity as the oil gets heated and also think it would take some very poor maintanence habits to sludge up an engine while using any of the better low cost oils these days but of course the chance is still there due to ever increasing operating temps by design .
 
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Right Motorbike, ISLAC, not API, starburst. You are correct on the phosphorus too. Even high mileage oil doesn't get us out of the phosphorus cap (at least not with Valvoline). Probably need to mix a quart of HDEO 15w40 into our PCEO 10w40 to boost the ZDDP level. As for 5w30 having more Group II, here is the durablend MSDS info including the lighter weights: 5w20 is 60-75 % hydrotreat/ 15-30 solvent dewax 5w30 is 54-64 % hydrotreat/ 10-20 solvent dewax 10w30 is 23-33 % hydrotreat/ 51-60% solvent dewax 10w40 is 74-84 % hydrotreat 15w40 is 23-33 % hydrotreat/ 51-61% solvent dewax So with some brands a move from 5w30 to 10w30 could be a step down. Valvoline Maxlife, is the same across the board 63-73% aliphatic petroleum distilled and 12-22 % synthetic lube oil (CAS 68037-01-4 indicating PAO) and no Maxlife 5w20.
 
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Originally posted by TallPaul: So with some brands a move from 5w30 to 10w30 could be a step down.
Yep , it sure can be .That's why I recommend 5w-30 everytime over a 10w-30 . They are both 30wts when hot anyway and cost the same . BTW , to read this article it would leave one to believe a poor DI package , base oil or both along with running too many miles would be more suspect to sludge making than a VII like Chevron's Paratones or Shells Shelvis or others . Marked 9 through 13 should be sufficient as topic information trails off from there . Markes # 11 is of interest though . Now which low cost dino's have the big additive packs and which have so-so additive packs and how are they performing through analysis here at BITOG ? [Wink] PDF [ July 17, 2004, 08:50 AM: Message edited by: Motorbike ]
 
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In 1991 my new car's owner's manual said 10w40 is not recommended for any temperature range. Why would they say that in 1991? That's why I don't buy 10w40 now but I realize that's not a good reason. That engine design was a failure because the valve guides wore out fast and passed oil.
 
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quote:
Originally posted by Motorbike:
quote:
Originally posted by TallPaul: So with some brands a move from 5w30 to 10w30 could be a step down.
Yep , it sure can be .That's why I recommend 5w-30 everytime over a 10w-30 . They are both 30wts when hot anyway and cost the same.

Definitely a step down in base oil quality. Would be interesting to see side by side tests of how the two hold up under stress. Which would suffer the most permanent viscosity collapse and which would produce the most sludge? Would the thicker Group I base hold up better than the thinner, Group II fortified oll or vice versa?
 
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I am not sure of this but I suspect you could be correct that the same basestock is used and the higher viscosity is achieved not only through viscosity modifiers, but by some kind of size exclusion process that would increase the amount of higher molecular weight component in the 10w-40. In general I think it safe to assume that your thermal properties, i.e. Noack and FP should improve with higher Mw. However, if the Mw blend isn't narrow enough and overly broad with a lot of viscosity modifiers, I think one could easily lose the added bonuses of the increase in high Mw components. I think these properties may be very dependent on the processes each company using to obtain their multi-grade oils. I will throw this out there and see the responses I get--It isn't necessarily the average molecular weight of the base stock oil, but the narrowness/breadth of the molecular weight that may have the biggest effect on your thermal stability.
 
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quote:
Originally posted by lobo11: It isn't necessarily the average molecular weight of the base stock oil, but the narrowness/breadth of the molecular weight that may have the biggest effect on your thermal stability.
Synthetic motor oils, whith their tight molecule size distribution (actually all same size for all intents and purposes) provide strong support your statement. Likewise a 10w40 made from mixing 4 qts 5w30 with 2 ats 20w50 would be inferior to a manufacturered 10w40 of the same brand.
 
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TallPaul--That being said, I think it very possible through size exclussion to see group III's like Syntec achieve very impressive thermal stability. I hope to use my homemade Noack test to come to a better understanding of this. I suspect that even a full/mostly full sythetic's thermal stability could be very dependent on the tightness of their synthesis process, or even variations in how A, B, and C oil companies synthesis their group IV synthetics.
 
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Yes, I'm pretty sure this subject has come up before, I think most of the bad rap 10W-40 gets is from early formulations using lousy, unstable viscosity index improvers which made a mess of many an engine decades ago. As was said, it's probably OK today for most users today, but I still wouldn't use it with the other weights available. I seriously doubt most oil companies are putting their best stuff in 10W-40 ... or 20W-50, for that matter. These are obsolescent weights and virtually no manufacturers in North America call for them. If I were an oil blender, I'd be worrying more about current and future EPA/API standards and newer vehicles still under warranty than oils no longer recommended. Chevron stated on their website that they use Group II+ in their 5W-30 and 10W-30 weights of Chevron Supreme, not in any other (10W-40, 20W-50, etc ...). For 5/10W-30, that should be 100% hydrotreat ... as compared to the mixtures cited above. That might also help explain why Chevron 5/10W-30 stays in grade out to 4,500 miles while their 10W-40 will show thinning well before this mark. [I dont know] And I would still recommend a 10W-30 over a 5W-30 in warm weather. Just look at the volatility rates for both weights. I checked Schaeffer's synthetic blends and if my memory isn't too far gone, the 10W-30 had half the loss rate of 5W-30. And I have serious doubts that after switching from PAO to Group III, Valvoline would be adding (more expensive) PAO back into one of their formulation. I guess I just don't trust the spec sheets to accurately reflect the formulations ... which seem to change on a monthly basis. [Frown] In short, if I want a 40 weight oil, I'll go with a 15W-40 dino or a 5W-40 synthetic for cold weather. Either would be better than 10W-40. --- Bror Jace
 
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I couldn't agree more. With modern chemistry, 10w-40 is a great weight the excessive VII issue is of the past except among Dino oils. If you look at Valvoline Durablend 10w-40 you have few VII's (Based on the VI) a good HTHS, good detergency and 3 seasona cold start flow ( except in south where it thin enough all year). Fred.. [Smile]
 
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Im currently testing the 10W-40 Maxlife against two runs previously of 10W-30. I will post my results. [Smile]
 
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Bror Jace, I think someone posted the base oils for Motorcraft/Conoco and it also had more Group II and III in the lower grades. So it can go both ways. -T
 
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quote:
I seriously doubt most oil companies are putting their best stuff in 10W-40 ... or 20W-50, for that matter. These are obsolescent weights and virtually no manufacturers in North America call for them
True. But...North American manufacturers may be becoming obsolete themselves! Asian mfg. are picking up US market share, big-time!, and I noticed my new Kia (with affiliate Hyundai the fastest growing car companies selling in America) with 3.5L V6 calls for, uh, 10W-40. And/or a 10W-50, but I have no idea where to get a 10W-50! So, maybe the 10W-40's time is not up yet. Also, who could object to the synthetics? Amsoil's 10W-40 rates high with a number of BITOG posters.
 
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My wifes 3.0 V6 1992 Aerostar consumes about a quart every 1500 miles on 30 weight (5w and 10w). I may try 10w40 next summer to see if the consumption drops. Seems to have done that in my pickup when I switched from 5w30 to 10w40. Thicker oil tends to have a higher flash point and presumably a higher NOACK volitility.
 
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There is nothing wrong with 10W-40's especially synthetics, if you take a look at all the new synthetics you'll see 0W-40's and even 10W-60's, 10W-40 doesn't have that much of a spread, especially when we are talking about synthetics, for a dino, sure I would stick with something with less spread, but for synth it is a non-issue. Btw, my favorite 10W-40 is Syntec, nice low 40 wt with good additive package [Smile]
 
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