Mixing oils?

Messages
90
Location
Indiana
I saw here a few days ago where someone suggested mixing Mobil 1 10W-30 with 25% 15W-50. Or say, if you needed to top off oil in case of it being low between changes you might add the 15W-50 to the 10W-50. Does this go for any oil you use. For instance, I use Redline 10W-30. So, if I needed to add 1/2qt in between changes, could I add 15W-50? And would this be of any help to slow the consumption? Rando
 
Messages
11
Location
Wellington, New Zealand
In theory it would help consumption a bit. Personally i wouldnt mix oils. At the next change i would go to 10w40 redline if i were you and in the mean time with the oil you have just add 10w30 redline till the next change.
 

Al

Messages
19,168
Location
Elizabethtown, Pa
I'm sure most people "in the know" would not recommend mixing. However like anything else...if you have the facts and can apply them in a reasonable fashion-go for it. As long as you are using the same brand and you want to up the viscosity a bit. .. plain old common sense tells you thet adding a 25% quantity of 50 wt to a 30 weight will bring up the viscosity. I am probably the one who mentioned this. When I did an analysis my viscosity was an upper 30 wt (11.25) Oil consumption was reduced . http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=3;t=000292
 
Messages
885
Location
North Carolina
I normally start "thickening up" the oil in my vehicles after they get about 50k miles on them. I swap a qt of 20w50 for a qt of 10w30 normally. I check my fuel mileage every tank of gas, and I do not notice any decrease in fuel mileage when I "thicken up", I have even noticed increases frequently. It works for me. Rando
 
Messages
1,992
Location
Windsor,Ontario
My engine calls for 10W-30...I put in 4 quarts 10W-30 and 2 quarts 15W-50(sump holds 6 all-toll)...came up with a 11.8W-36...using Mobil oil in the SuperSyn variety only...Mobil's web page said it's allright to do so...just do this in the summer and they(two 4.0L Jeep motors) are running fine...piston slap is down a bit and hot idle pressure is up a tad...the 10W-30 Mobil does start out a bit thin in the first place...just tried an experiment with mixing the two oils (more SuperSyn in the 15W)to get viscosity up a smidge...and everything is good to go.
 

Patman

Staff member
Messages
21,989
Location
Oakville, Ontario
quote:
Originally posted by Greaser: My engine calls for 10W-30...I put in 4 quarts 10W-30 and 2 quarts 15W-50(sump holds 6 all-toll)...came up with a 11.8W-36...
It doesn't quite work out that way for a few reasons. One, there are no such things as those weights listed, two, mixing two oils of different viscosities won't always result in an obvious viscosity, due to the different levels of VII in the oils and how they react with each other. Also, if the 10w30 is on the thin side of the 30wt while the 50wt is on the higher side, this changes things around too. Best way to determine the viscosity of mixed oils is to do a UOA very soon after putting it into your engine. It's best if you can get the viscosity at both 40c and 100c.
 
Messages
1,992
Location
Windsor,Ontario
quote:
Originally posted by Patman:
quote:
Originally posted by Greaser: My engine calls for 10W-30...I put in 4 quarts 10W-30 and 2 quarts 15W-50(sump holds 6 all-toll)...came up with a 11.8W-36...
It doesn't quite work out that way for a few reasons. One, there are no such things as those weights listed, two, mixing two oils of different viscosities won't always result in an obvious viscosity, due to the different levels of VII in the oils and how they react with each other. Also, if the 10w30 is on the thin side of the 30wt while the 50wt is on the higher side, this changes things around too. Best way to determine the viscosity of mixed oils is to do a UOA very soon after putting it into your engine. It's best if you can get the viscosity at both 40c and 100c.

I was just joking at the 11.8W-36 viscosity guess Patman...I'm using the Mobil oil in both cases of mixing here and wouldn't have done it if their web site said this wasn't advisable...they said go ahead if you want...I just wanted to thicken my mix up a bit for summer.
 
Messages
951
Location
Loveland, Colorado
Hi Rando, I'm a little uncomfortable mixing different brands, but in an earlier exchange (this past December) about this topic, one of our members had this to say: quote: -------------------------------------------------- Originally posted by nick778: I sent Redline an email asking the same question to their tech dept. The reply from them said their synthetic street oils mix very well with Mobil 1 synthetic in terms of both base stock and additive package. -------------------------------------------------- Based on this info, it appears as though you should have no problems. You might try emailing RedLine & asking them directly if you're at all unsure about it.
 
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