Mixing 20w50 and 5w20

[dlundblad]

Assuming the same brand was used, what viscosity would this oil be?

Say I use my Jeep's 6 quart sump and was to add 3.5 quarts of 20w50 and fill the remaining 2.5 with 5w20. If i did everything right, the final viscosity should be about a 33.28 at 100*C according to this.

Would the w be about 13.75 and thus a thicker "30" weight comparable to the Delo 15w30?

3.5 (quarts) x 20 (w)= 70
2.5 (quarts) x 5 (w)= 12.5
12.5+70=82.5 then divide by 6 quarts
= 13.75?

 

[MolaKule]

If the calculations are correct, that would be a 40 grade at 100C.

 

[A_Harman]

Originally Posted By: dlundblad
Assuming the same brand was used, what viscosity would this oil be?

Say I use my Jeep's 6 quart sump and was to add 3.5 quarts of 20w50 and fill the remaining 2.5 with 5w20. If i did everything right, the final viscosity should be about a 33.28 at 100*C according to this.

Would the w be about 13.75 and thus a thicker "30" weight comparable to the Delo 15w30?

3.5 (quarts) x 20 (w)= 70
2.5 (quarts) x 5 (w)= 12.5
12.5+70=82.5 then divide by 6 quarts
= 13.75?



You can't do it that way! The grade numbers on the W-ratings are not actual physical quantities, and can't be predicted by the weighted calculation you have done. Mixing different W-rated oils leads to unpredictable outcomes. If you really want to know what W-rating that mixture would be, you would have to get it tested. I once asked a rep from an oil company what I would get if I mixed their 15w40 with their 5w20 50/50, and he said I would get a 40-weight at high temperature, but he didn't want to guess at the W-number.

 

[Rand]

Totally does not work that way. Depends on VI, and a number of other variables.. as well as the fact that 5w20 and 20w50 are viscosity ranges not a set number.

I would estimate it should be around a 10w40 but it would just be an estimate.

Originally Posted By: dlundblad
Assuming the same brand was used, what viscosity would this oil be?

Say I use my Jeep's 6 quart sump and was to add 3.5 quarts of 20w50 and fill the remaining 2.5 with 5w20. If i did everything right, the final viscosity should be about a 33.28 at 100*C according to this.

Would the w be about 13.75 and thus a thicker "30" weight comparable to the Delo 15w30?

3.5 (quarts) x 20 (w)= 70
2.5 (quarts) x 5 (w)= 12.5
12.5+70=82.5 then divide by 6 quarts
= 13.75?

 

[901Memphis]

You would need to know either the 40c or 100c viscosity of each oil and plug the numbers here.

http://www.widman.biz/English/Calculators/Mixtures.html

 

[stchman]

Simply using ratios you would have:

13.75W-37.5

I'd like to see that on a quart bottle.

 

[TFB1]

Originally Posted By: dlundblad
Assuming the same brand was used, what viscosity would this oil be?

Say I use my Jeep's 6 quart sump and was to add 3.5 quarts of 20w50 and fill the remaining 2.5 with 5w20. If i did everything right, the final viscosity should be about a 33.28 at 100*C according to this.

Would the w be about 13.75 and thus a thicker "30" weight comparable to the Delo 15w30?

3.5 (quarts) x 20 (w)= 70
2.5 (quarts) x 5 (w)= 12.5
12.5+70=82.5 then divide by 6 quarts
= 13.75?

Way off the mark, a oil that had a cSt of 33 @ 100c would be approx a light 80 weight if such existed, 26.3 is upper limit of a 60 weight...

Take a look at these Mobil Special oils to get a idea of what each grade can be...

http://www.mobil.com/USA-English/Lubes/PDS/NAUSENPVLMOMobil_Special.aspx

Using the Widman caculator 50/50 of 5W-20 & 20W-50 would be 12.58 or right at the 30W - 40W break...

 

[mjoekingz28]

So whaddaya call STP oil treatment with a 100 degree cst of 250?

 

[OVERKILL]

Originally Posted By: mjoekingz28
So whaddaya call STP oil treatment with a 100 degree cst of 250?


Junk. LOL!!!

 

[Shannow]

Originally Posted By: mjoekingz28
So whaddaya call STP oil treatment with a 100 degree cst of 250?


an ADDITIVE...not a grade of oil.

ADDITIVE, something that's added to oil in small amounts to change it's properties.

e.g. Afton PMA pour point depresent is 450cst at 100C, doesn't qualify as an oil grade, and is ADDED to oil at small treat rates, like 1/10 of a percent.

Lucas is also an additive...and OVERKILL is probably pretty close to the mark on that one also.

http://cdn2.hubspot.net/hub/68152/file-1...r_ball_0709.pdf

 

[SilverC6]

Originally Posted By: mjoekingz28
So whaddaya call STP oil treatment with a 100 degree cst of 250?


In 1972, if you did an oil change and didn't add STP, you were being negligent.

The Racer's Edge....