As I was replacing the oil in my engine after a change I noticed that one of the quarts said 10w-40.. All the other ones were 10w-30. I pulled all 5 quarts off the same rack at the parts store and it must have been a mistake made by an employee, or it could have been intentional I don't know.. But I was wondering if I have anything to be concerned about?

 

Nah - just make sure you use the right stuff next oil change.

 

I wouldnt worry about it, I would maybe worry if it were a non detergent or like a wieght that was straight 50 or something. Your fine.

 

Others might feel different, but I wouldn't be the least bit concerned. I can see no cause for any alarm.
I ask myself: what adverse side effects could this create?
I answer myself: none (that I can think of).

There is the issue of the 30 spread between 10 and 40, but for 1 qt out of 5, and just for one oil change, I'd not give it a second thought.

Of course you could just drain that one qt of 10w40 and replace it with a qt of 10w30.

 

Not to worry. You still are running 10w30. The single 10w40 will average out to pull you a bit higher in the 30w range. I don't normally mix oil types, but right now happen to have 4 qts of 5w30 and 2 qts of 20w50 in my crankcase, and then topped up with 10w40. It all figures to 10w40. Why would I do such a crazy thing. Long story. If anybody cares, I will elaborate. Suffice it to say, I am switching from 5w30 to 10w40 as it does my oil pressure better.

 

Alright. Thanks guys.