Mixing Different Weights

[SpitIX]

I have accumulated a couple of quarts each of different weights of Pennzoil, 5W-20, 10w30, 15W40.
I have a ton of 5w30.
I want to use up the odd quarts but am not sure what weights equal what when mixed. Would like to end up with something resembling 10w30 or 5w30 when mixed.
Anybody have the formula?
Thanks.

 

[Al]

http://www.baseoils.shellglobalsolutions.com/calculations/blending_pop.asp

 

[Curious Kid]

I believe there was a link in one of the threads somewhere that had you put in the various viscosity values and so forth, and it would then give you a calculated value based on that and the ratio that you desired to mix them in.

I ponder if it could be just as easy to average the values yourself.

Hypothetical example:
I mix 2 quarts of one oil (vis.@40:70, vis.@100:11, HTHS@150:3.2, vis. index: 160), with 3.5 quarts of another (vis.@40:90, vis.@100:13, HTHS@150:3.6, vis. index:150).

Take each value and multiply them by the coresponding number of quarts for each oil, then add these number, and then divide by the total number of quarts. Essentually what one is doing here is averaging the values.

Example Cont.
Vis.@40=((2x70)+(3.5x90))/(2+3.5)...82.7
Vis.@100=((2x11)+(3.5x13))/(2+3.5)...12.3
HTHS@150=((2x3.2)+(3.5x3.6))/(2+3.5)...3.6
Vis. index=((2x160)+(3.5x150))/(2+3.5)...153.6

This works great in Excel by the way.

 

[Curious Kid]

Thanks for the link Al.

I ran the numbers to find that it isn't quite so simple as calculating averages. Just goes to show how valuable "theories" can be, albeit not very indepth as far as molecular knowledge/fluid dynamics goes...I'm no scientist by any means.

 

[Curious Kid]

Perhaps it does work, I mean it helps if one actually puts in the correct numbers to make an accurate go for comparison sake.

 

[TallPaul]

If you mix them in equal parts it pretty obviously will come out as a 10w30. I put ballpark numbers in of 9, 10.5, and 14 cSt for the 20, 30, and 40 wt and got a mixt viscosity of 11 cSt at 100C--a pretty solid 30 weight. Go for it since summer is comming. Winter I would not run it.

 

[Triple_Se7en]

What happens if "some of us"... including original poster SpitIX don't know how to operate that calculator hyperlink. Plus... I'm sure his Pennzoil bottles don't have viscosity numbers on them to punch into this calculator. Only regular posters here knows there's a viscosity breakdown on the mainpage. When I give someone a calculator like that, I'll show him how to use the calculator first by directing him to the mainpage.

SpitIX

To offer you simpler, oldfashioned help, tell us exactly what oddball quarts you have & how big your motor crankcase is. That's a much simpler starting point.

[ April 06, 2005, 01:10 PM: Message edited by: Triple_Se7en ]

 

[SpitIX]

quote:

---

Originally posted by Triple_Se7en:
What happens if "some of us"... including original poster SpitIX don't know how to operate that calculator hyperlink. Plus... I'm sure his Pennzoil bottles don't have viscosity numbers on them to punch into this calculator. Only regular posters here knows there's a viscosity breakdown on the mainpage. When I give someone a calculator like that, I'll show him how to use the calculator first by directing him to the mainpage.

SpitIX
To offer you simpler, oldfashioned help, tell us exactly what oddball quarts you have & how big your motor crankcase is. That's a much simpler starting point.

---

Seven:
Thanks for the help. I took one look at the calculator and went to lunch. ;-)
I have on hand:
5W-20, 5 Quarts
5w30, Many quarts
10W-30, 3 Quarts
15W-40, 4 quarts
20W-50, 5 Quarts

Crankcase capacity is either 5 quarts or four quarts.
Thanks.

 

[TallPaul]

Don't know what grade your car specs, but 20w50 surely would be too thick. Wonder if you can return it for exchange. May not even need a receipt.

 

['00obw]

Let's see...I've mixed Mobil 1 10w30 with Amsoil S3K 5w30, Chevron Supreme 10w30 with Mobil 1 Truck and SUV and later added Pennzoil 30wt HD, Motorcraft 5w20 with Mobil 1 Truck and SUV, Motorcraft 5w30 with GC, Motorcraft 5w20 with 5w30 (UOA on this one), and now GC with Mobil 1 0w20. I don't think I run a non-mixed oil since my first oil change and that was Mobil 1 10w30. The car hasn't died yet