What makes a 10w-30 better than a 5w-30?

Messages
244
Location
Shelby, NC
I keep hearing that oils such as Mobil 1 10w-30 are better than their 5w counterparts, what makes this so? There are several oils (Pennzoil among them) where the 5w dino is actually heavier than the 10w counterparts at operating temp. For short trips the 5w would seem to be much better in terms of start up flow and what-not.
 

KW

Messages
1,686
Location
Central Arkansas
I'm glad you asked this because I have sort of been wondering myself. 5W30 is bad, 10W30 is good, and 0W30 is better. 10W40 is bad, 0 and 5W40 are good. etc. I am only thinking of synthetic oils.
 
Messages
4,632
Location
Decatur AL USA
The Base Stock used to produce a oil are generally much more robust than the VII (Vicosity Index Improvers). In general assuming oils use the same base stock (Cat II Dino) with closer spreads such as, 5W20, 10W30, and 15W40 require less VII so are more stable and less likely to shear to a lower Vicosity. When oils sheer they can create sludge. 5W30 has the additional problem in that in designing the oil to meet the API Energy Conserving Classification they are designed to sheer rapidly to a lighter weight to increase fuel mileage. In my opinion you would be better off to start with a 5W20 than a 5W30 if you want a oil with good cold start capability so as to reduce the possibilty of sludge formation since you basically are going to have 5W20 after 1000 ml anyway. You can also move up to a oil made with a better base stock such as US Castrol Syntec 5W30 (Cat III ) Mobil 1 5W30 (Cat IV) or German Castrol Syntec 0W30 (Cat V). I am sure that if I have made some drastic error in this explanation one of the real experts will be along to correct it. Gene
 
Messages
11,284
Location
Spring HIll
quote:
Originally posted by Gene K: I am sure that if I have made some drastic error in this explanation one of the real experts will be along to correct it
Gene, I'm not one of the experts, but your explanation looks excellent to me! [Cheers!]
 
Messages
97
Location
OH
i always thought that 10w30 was better than 5w30 in everything because that is what everybody said and because there is so much more 10w30 on the shelfs. this is until i took an engineering physics class. in this class we debated this topic long and hard and looked at many facts. and IMHO 5w30 will protect better than 10w30 because the 5w30 will help protect during startup a lot better than 10w30. and by running a thinner oil fuel mileage should increase as well. i would use 5w30 or 5w20 over 10w30 in a gas vehicle. i use 15w40 in my diesel right now and would like to switch to a 5w40 but am worried because i already have a leaking issue. [Patriot]
 
Messages
524
Location
Central Oklahoma
The folks at RedLine say on their website the 10W-30 should be picked (over 5Ws) if "maximum durability" is desired. But I don't know if that is a reference to shear stability, stay-in-grade, or whatever. Reportedly, the AMSOIL 10W-30 has less, or no, VIIs.
 
Messages
72
Location
Chicago
quote:
Originally posted by steiner43511: i always thought that 10w30 was better than 5w30 in everything because that is what everybody said and because there is so much more 10w30 on the shelfs. this is until i took an engineering physics class. in this class we debated this topic long and hard and looked at many facts. and IMHO 5w30 will protect better than 10w30 because the 5w30 will help protect during startup a lot better than 10w30. and by running a thinner oil fuel mileage should increase as well. i would use 5w30 or 5w20 over 10w30 in a gas vehicle. i use 15w40 in my diesel right now and would like to switch to a 5w40 but am worried because i already have a leaking issue. [Patriot]
I'm not sure if protects "a lot better at startup" is the right term. Mobil 10w/30 pours to 45 below. We are not exactly describing a thick poor performing start up oil here.
 
Messages
780
Location
Palatine IL
Pour point and viscosity or pumpability at normal start temps is quite different and a 5w should be easier on the oil pump and flow better at start temps we are actually going to see in our cars. It's what gets the spec and a dino 5w should still cold pump better than a synth 10w except in extreme conditions.
 
Messages
3,118
Location
San Antonio, TX
I think it depends on the application. A high revving engine like a 2.0L 5 speed in a hot climate will benifit from using an oil with less VII additive. Can someone explain VI in M1? 5w30 has a high VI number but that's not due to additive. It's a characteristic of the group IV base stock?
 
Messages
8,937
Location
SC
quote:
Originally posted by jorton: Can someone explain VI in M1? 5w30 has a high VI number but that's not due to additive. It's a characteristic of the group IV base stock?
Correct. If the VI of the base oil is high enough, less VI improver (or in some cases no VI improver) is needed. The grades of Mobil 1 that PROBABLY have no VI improver: 0w20, 10w30, and 15w50. The other grades have some, but not nearly as much as a conventional oil.
 
Messages
1,130
Location
California
quote:
until i took an engineering physics class. in this class we debated this topic long and hard and looked at many facts
What facts were you looking at? Real information, or theoretical musings based on ideal oil assumptions? John
 

ncirish

Thread starter
Messages
244
Location
Shelby, NC
Ok, there is a second part to my question then. What is the difference in the pour point and the pumpability? In NC we generally use a 10w oil year-round. BUT if a 5w is better for short trips (5 miles or less) then I have to rethink my oils.
 
Messages
1,139
Location
USA
^ yep, i use 10w30 M1 year round. if 5w30 is that much better in the winter, i might have to increase my stockpile. [Smile]
 
Messages
72
Location
Chicago
quote:
Originally posted by goodvibes: Pour point and viscosity or pumpability at normal start temps is quite different and a 5w should be easier on the oil pump and flow better at start temps we are actually going to see in our cars. It's what gets the spec and a dino 5w should still cold pump better than a synth 10w except in extreme conditions.
OK I buy that. But my car sits in a garage that never sees anything below about 60 degrees. It's not a daily driver so it doesn't sit out in the cold. Do I really need a 5W synthetic oil? I'd rather stick with at least 10W30 Mobil 1.
 
Messages
13,132
Location
By Detroit
quote:
Originally posted by ncirish: I keep hearing that oils such as Mobil 1 10w-30 are better than their 5w counterparts, what makes this so?
The 10w30 is Mobil's "High Mileage" synthetic. From their website: "Mobil 1 with SuperSyn™ is available in five viscosity grades: Mobil 1 with SuperSyn™ 10W-30 – Higher-Mileage Vehicle Formula Mobil 1 with SuperSyn™ 5W-30 – Newer Vehicle Formula Mobil 1 with SuperSyn™ 15W-50 – Performance Driving Formula Mobil 1 with SuperSyn™ 0W-30 – Enhanced Fuel Economy Formula Mobil 1 with SuperSyn™ 0W-40 – European Car Formula" http://www.prod.mobil1.com/index.jsp
 
Messages
9,448
Location
USA
steiner4531, on a 50 degree morning how much faster do you think a 5W30 is going to get to the parts over a 10W30? Is it a nano second, two nano seconds etc????????? How much faster is it likely to shear down to a 20Wt? What amount of protection is lost once it shears down out of grade? How do the long term deposits that boil off and deposit themselfs in the engine effect longterm durability? Mind you are primarly reffering to convetional 5W30 and 10W30. When we move over to synthetic oils the difference is still their but it is much less. M1 10W30 usualy beats it 5W30 brother in UOA everytime on the same vechile. Mind you it beats it by such a small margin that the margin for error is sometimes greater then the amount of victory. THe fact remains though that it still wins. It tends to require less additional oil between oil changes as well. We see this with the M1 OW30 as well. You would have to limit the parameters of a discusion an awful lot to saw that 5W30 is better then 10W30! How quickly it can flow to parts is only one factor. I still have not had antone bring forward any research that documents how much faster a 5W30 floes to engine parts as compared to 10W30 at any temp. let alone the ones we see most of the time wich are well above -25F and -35F. We have synthetic 5W40's that can flow and pump better at -25 then some convential 5W30 oils. We also have some 0W30's now that are real players.
 
Messages
189
Location
Northern Colorado
In regards to oil vis at start up I would think a thinner oil would get to where it's suppose to be faster, although by how much is in question. A couple things to think about at start up. -Wouldn't a thinner oil get to the piston/ring/cylinder/wrist pin faster. It is my understanding that most gas engines have no oil supply to the underside of the piston other than the oil that is splashed up or thrown out of the rod and main bearings. Seems like a thinner oil would get there faster and in larger quantities? -A thinner oil would also slightly decrease oil pressure which might keep the bypass on the filter from opening as much or maybe at all during warm up. If 80%(or whatever that one study stated) happens at start up, any little bit would help. Pre-oiler anyone? Just some ideas I had. Seems accurate to me. Input?
 
Top