Mixing 2 brands of 5w-20 oil?

[2013AccentGS6MT]

I changed the oil at 2,000 miles, and yesterday at 5,000. The first change I used Pennzoil Platinum, and the 2nd I used Castrol Edge because the store was out of the Pennzoil in 5w-20. Both are full synthetic and expensive at about $10 a quart. Now I have 1.5 quarts of each left over. Can I combine them when I do my next change at 10,000 miles or is that a bad idea?

[Danno]

No issues with doing that.

[someguy]

I agree and Im planning to do the same thing. My next oil change will be a mix of Pennzoil Platinum, Pennzoil Ultra, and Quaker State Ultimate Durability. I always use synthetic and buy whatever has a sale or rebate.

[rattlecanned]

Mixing brands wont make a difference, just never mix weights.

[hoosieraccent]

I've read up a lot about this, varying opinions on the subject it seems. Some say go ahead, others say don't, while a few say stay within the same manufacturers to keep the same add packs in there to avoid "additive clash."

I've done it before - with cheap store brand conventionals even - and the car still runs... Mixing doesn't particularly give me any cause for concern.

[fsv87]

Shouldn't have a problem as long as it's all 5w20.

[Past racer]

I will add something from quite awhile back (don’t remember source, just some details). It was about engine bearing failure being attributed to mixing of oil brands. It pointed out the failure was caused by a chemical reaction between two additives that where in different brands of oil. It indicated that mixing many additives manufactures put in their oil would not cause a problem, but on occasions the mixing takes a toll on lubricating qualities. I remember it saying that mixing different weights or dino and synthetic of same brand was not a problem, because manufactures test to make sure there is no reaction between additives they use in all their oils. In summary it wasn’t the oil bases that were the problem but the additives.

Something like nitro and glycerin are ok by themselves…. But putting them together might get your attention.

[2012AccentSE]

Should be ok. I have done it in the past with no issues to speak of.

[isd.jwendell]

Tough call for me... The chemist in me says don't mix, but why not? When you change the oil, completely draining it doesn't really drain all of the old oil. So, switching from one brand to another will cause mixing. Synthetic oil had to be compatible with regular oil for this reason. However, that mixing is not the same as a 50:50 mix. The old oil will eventually get diluted, unless you constantly alternate between the two brands. So, is it worth the potential problems (not saying that you would see any)?

[mrmr256]

I have about 1/5 a quart of Quaker State Ultimate Durability and 3 quarts of Castrol Edge, both are same weights. I has the QSUD laying around and didn't want it to go to waste.