another mixing Q

[bigbrother8]

i just bought 5 quarts of 5w30 formula shell for my 2007 mazda that takes 6 qts. i have a quart of valvoline synpower in 5w40 that is SL rated and was wondering if i should throw it in with the 5 qts of shell or just go and buy another quart of the shell to make the 6. also if someone could do the calculation for me http://www.geocities.com/CapeCanaveral/3655/VI.html
my browser wont work with this java app for some reason.

5 qts of 66.16 - 40 deg C and 10.75 - 100 deg C
and
1 qt of 89.0 - 40 deg C and 14.5 - 100 deg C


TIA

 

[Dad2leia]

Not the calculator you're looking for. It doesn't give the ability to figure the new viscosity for mixing the two oils.

 

[02zx9r]

I would throw it in there. Should not be any problems what so ever

 

[flatlandtacoma]

The calculator you are looking for is here:

http://www.shellglobalsolutions.teshosting.co.uk/calculations/blending_pop.asp

 

[Dad2leia]

Thanks flatlandtacoma. I bookmarked the thing this time!

 

[Merkava_4]

Originally Posted By: flatlandtacoma
The calculator you are looking for is here: http://www.shellglobalsolutions.teshosting.co.uk/calculations/blending_pop.asp


That's the one I use too, but I this time I can't figure out what percentage 5 is of 6. I'm guessing maybe it's 80% or 90%; don't know for sure. I need to go back to 6th grade I suppose.

 

[Merkava_4]

Quote:
5 qts of 66.16 - 40 deg C and 10.75 - 100 deg C
and
1 qt of 89.0 - 40 deg C and 14.5 - 100 deg C


I consulted a math tutor and used Shell's calculator to come up with:

69.6 Centistokes at 40C
11.3 Centistokes at 100C

Viscosity Index is 156

 

[TallPaul]

It's not an issue. Calculating the new viscosity is an academic exercise (but I do it anyway for fun). It won't raise it enough to matter. You'll actually have a thicker 30 wt, more like 30 wts used to be. The mix actually sound like a great idea and should be repeated every oil change.

BTW you can calc the new viscosity with a pocket calculator so long as it has log function. The new viscosity is the anti-lot (inverse-log) of the weighted sum of the logs of the separate viscosities. This is what the linked calculator uses. Bear in mind that equation is for base oils, so may be less accurate when used for oils with VII added, but should be close enough.

Your weights are simple

5/6 = 0.83 and 1/6 = 0.17

 

[bigbrother8]

i made a mistake in thinking the quart of 5w40 synpower was SL rated but it is SJ rated, still ok to mix it with the SM stuff for my '07 my vehicle?