Another Oil Question

[MysteryTheatre]

I am trying to educate myself here on the many facets of engine oil. in a previos thread i learned various acea ratings on 15 w 40 prove to have high shear stability. it appears shear stability is the primary concern for the flat cam buick.
to protect my engine , and maybe yours too, i researched further the shear stability rating, most oils on there product data sheets have a viscosity index
this is the resistance to viscosity /shear break down i found a number somewhat near 150 to be exceptionally high compared to most oils. even the commercial deisel 15w 40's had indexes of 138 ...ect... which is probably good enough. does this viscosity index tell the whole story on shear stability? if so i will share with you the results of my findings. what oils are the highest...
but i believe there must be more to it?

[LANDY96]

You know, I am starting to hear about this more and more! Im the Asst. Mgr. for a local Autozone. I get alot of the gear-heads who have hot rods in the store and they are asking about this situation. I think i will research this even more as well! I hear that the highest rated oil is the Rotella T 15-40 for diesels. I recently rebuilt my D1, and the lifters had a circular indention on the bottom, where the camshaft hit it. Maybe not so strange.......?

[Elemental]

You are braking up the right tree! The shear resistance is what prevents the lifters from smacking into the cam. You are right, the higher, the better for your flat tappet camshaft.
Roller cams/lifters, like most moderns engines its not as crucial.

[MysteryTheatre]

the highest Viscosity index i could find on any oil was amsoil and royal purple @160 ! but for a third of the Co$t Valvoline Maxlife boasts a shear index of 158!!! the next highest is Valvoline conventional @ 151. Phillips 66 as well as Super 76(both texaco) have an index of 150. every other big name oil i looked up as well as some smaller brands have indexes that are anywhere from the low 140's to scary low 130's to even scarier blank (not published) viscosity indexes . The numbers above are for 10w40. lower viscosities usually have higher indexes for the same oil. therefore higher viscosities , above 10w40 , viscosity index' could be above or around 140 and be acceptable. i found most commercial rated 15 w 40's to be in the 140ish ballpark , which should hold up good. i was unable to find rotella's viscosity index , but i know delo 400 , delvac 1300 super and tection xtra were all right around 140. now with that said , what exactly is this number(how is it determined) ? i guess they shear try to shear the molecules by pumping it through a diesel injector nozzle? all i know is the higher the number the better...

[msggunny]

Originally Posted by MysteryTheatre

the highest Viscosity index i could find on any oil was amsoil and royal purple @160 ! but for a third of the Co$t Valvoline Maxlife boasts a shear index of 158!!! the next highest is Valvoline conventional @ 151. Phillips 66 as well as Super 76(both texaco) have an index of 150. every other big name oil i looked up as well as some smaller brands have indexes that are anywhere from the low 140's to scary low 130's to even scarier blank (not published) viscosity indexes . The numbers above are for 10w40. lower viscosities usually have higher indexes for the same oil. therefore higher viscosities , above 10w40 , viscosity index' could be above or around 140 and be acceptable. i found most commercial rated 15 w 40's to be in the 140ish ballpark , which should hold up good. i was unable to find rotella's viscosity index , but i know delo 400 , delvac 1300 super and tection xtra were all right around 140. now with that said , what exactly is this number(how is it determined) ? i guess they shear try to shear the molecules by pumping it through a diesel injector nozzle? all i know is the higher the number the better...

Thats good info to know. I just put RP in the Disco.

Where did you find the info on this? Want to look into what the shear is for Castrol Syntec 10w 40.

[OkieRover]

I found this page.
I don't know any of these numbers.
BUt it has some comparison.

I'm a Castrol 20w50 man. Always will be.

AMSOIL vs Castrol, Valvoline,Mobil, Pennzoil,

[Elemental]

Originally Posted by OkieRover

I found this page.
I don't know any of these numbers.
BUt it has some comparison.

I'm a Castrol 20w50 man. Always will be.

AMSOIL vs Castrol, Valvoline,Mobil, Pennzoil,

I wouldnt use 20-50. Its not the best choice.
Read this entire thread.
OiL

[MysteryTheatre]

i painstakingly visited each oil manufacturer's website and brought up the "PRODUCT DATA SHEET". then i make a list and compared them all...yeah i have a life... no i just felt that was the only way to truly find out. I visited castrol's website and found almost all their oils have data missing from the viscosity index column... whats that say? to me that says it was a number that they'd rather not share with us. checked all the oils i could dream up... but there are so many you know? Hint: the PDS can be easy found , it usually has an adobe reader logo next to it...although some companies have required extensive digging to get to the real facts... i think my choice because of the age of my vehicle , is the philipps 66 i can get 10w40 for a buck fifty a quart!!! and a viscosity index of 150 is exceptional, their non-marketing no frills packaging works for me.

[Elemental]

You are a excellent student! To a fault, actually. I encourage you to learn as much as you can about specific oils....Like you are.

My experiance, in trying the same thing is that the specs changed too often for my list to be current. That isnt meant to discourage you from doing it. Its just my experiance. To me, it was more productive to give the tools to know what to look for, and you did a excellent job of absorbing a tough to grasp topic (At least it was for me)...So hats off to you! Good hunting!

[MysteryTheatre]

The hardest thing about understanding the viscosity index, is comparing oils of different viscosities... for example trying to compare rotella to royal purple.
the reason this is difficult is because three different viscosity oils from the same family IE: valvoline maxlife 5w30 , 10w30,and 10w 40 will have different viscosity indexes, with the lowest viscosity scoring the highest rating on the viscosity index. some people may have a hard time understanding why a 5w30 has a higher viscosity rating than its brother 10w40. the best way i can explain this is to say viscosity index is a resistance to viscosity Break Down. Just as a Large peice of glass can easily break into several smaller peices, these smaller shards are much harder to break down thus they recieve a higher index rating. so when comparing a 15w 40 to a 10w40 it is complicated, my best judgement tells me there should be a fine line... for me ... i think any 10w40 with a viscosity index over 150 is good oil. for a 20w50 (for those of you who live on mars) a viscosity index over 135 should do. and for the 15w 40 commercial oil i guess around 140 or better is good. many 5 w20's have indexes over 150 but that because to break them down anymore
involves nuclear fission !!! and 5 w 20 does nothing good for these beasts.
unless you live on neptune.

[OkieRover]

Originally Posted by MysteryTheatre

and 5 w 20 does nothing good for these beasts.

That's the oil my wife's Taurus calls for.
I think I put 10w30 in it last time.
She only drives it around town. It's a 2002 and just now has 48,000 miles.

[p76rangie]

I think you guys over analyse things. Yes, there are some oils that are better than others. But if you stay away from the real cheapies, you will not have too much to worry about in your Rover V8's.

Statements things like 20w-50 is no good, or SM grade oils are no good, should treated as generalisations with no real facts to back them up. Buy the oil that best suits the temperatures that you drive in and and how hard you work your vehicle.

To suggest that the viscosity printed on the oil does not reflect its shear capabilities is a bit strange as this is the test that they must past to determine the rating that they can put on the oil. The people above also do not mention how the oil pressure affects the shear capabilities of the oil. You can run low viscosity oil in engines that have higher oil pressures as it increases the shear aspects of the oil. To run them in low pressure engines like the Rover V8 is not comparable to running them in newer high pressure motors.

[Elemental]

Originally Posted by OkieRover

That's the oil my wife's Taurus calls for.
I think I put 10w30 in it last time.
She only drives it around town. It's a 2002 and just now has 48,000 miles.

I have documented cases of engine failures and denied warranty for this very thing! I would use....well, what the engine asks for. There is a reason that Ford and Honda went 5-20....Thats the correct part.

[Elemental]

Originally Posted by p76rangie

Statements things like 20w-50 is no good, or SM grade oils are no good, should treated as generalisations with no real facts to back them up. Buy the oil that best suits the temperatures that you drive in and and how hard you work your vehicle.

THink what you want. I tried to present it in a way tha tmost people here could understand. The fact is, 20-50 is a bad choice. Period Paragraph.

And, what are you basing your statements on, that the engine didnt explode in the first 5 miles after using a non spec oil. DUH! It accelerates wear OVER TIME.... Its just simply not going to last as long as it could. Period.

But, if you dont want to beleive what I say, I dont give a shit. Why should I. But, I know what I am talking about, and I presented it here. If you want to ignore it....Ignore it. Who cares.

But, there is more to oil then the S-rating and Viscosity...It just isnt that simple.

[gordo]

Funny Ive ran nothing but 20/50 in my 89 RRC for 10 yrs and it now has 300k on it. My wifes D1 has 156K and same oil, my driver 92 RRC has 174K and same oil. I use Kendall usually but once and awhile I will run Mobil one (15/50)> Also ive never had any of these motors apart. The key is changing the oil regularly and running good filters. Yeah it might not work in some cases but down here in FL I wouldnt even think of running any 10 weight anything oil. Its just too damn thin for the heat down here. Im betting not one of your "documented" breakdowns involved a Rover V8. Gordo.