I change oil on my 2006 Hyundai Sonata with 5W-30 motor oil and I use 5 qt containers.
Could I top off after adding the 5W-30 5 qts with 5W-20 motor oil of the same brand?
You won’t hurt a thing topping off the oil with 5W-20 of any brand.
It’s OK, but I would not change all the oil to 5W30.
No problem at all topping it off with different viscosity oils when they are of the correct grade.
Sure… you could add any brand and or any viscosity for that matter…
It depends how often you add oil. If you add oil every 1000 miles, you might have essentially all 5W20 by the time you change oil again.
Why is this question being asked, in the first place?
I’m assuming the owner’s manual calls for 5w30?
And maybe OP has some 5w20 in the garage, which they want to use up?
The correct answer, as far as I’m concerned, is to use the viscosity listed in the owner’s manual . . . for oil changes AND top ups
If you know you are going to need to add oil, why not just buy a couple extra quarts to begin with. Or is that too easy?
If you know you are going to need to add oil, why not just by a couple extra quarts to begin with. Or is that too easy?
You run the risk of the crank-case hitting the oil as it turns. This will cause a whipping of he oil and that is NOT good. The oil gets thick…an the pump becomes unable to pump it…thus destroying your engine.
He didn’t say add extra quarts. He said “by” (buy) extra quarts… 
oop…missed that.
Wow, @Mike. The year is only half gone and here’s your first faux pas. I’m sure that someone is keeping score and you’ve got some serious catching up to do.
I think I have been guilty of this a time or two,seems to cause no great harm,just make sure you dont add oil thats too thick.Sometimes I even mix brands a little bit,as long as the additives dont have some kind of chemical reaction(a lot of house brands have the same manufacturer anyway)just dont make a habit of it,now heed this however-some lubricating greases,with a different metallic base,should never be mixed,eg; sodium and lithium.
What oil(s) does the owners manual specify? If both of those viscosities are specified, it will not hurt to mix them.
Years ago I heard it said that the lesser-range oil (5W20 in this case) is slightly preferable because it has less viscosity enhancer and more actual lubricity. That may be true but how significant, I don’t know.
I purchased a new Ford Tempo back in 1985. The manual called for 5W-30 oil, but that viscosity wasn’t readily available back then as most everyone used 10W-30. I asked the service manager and he said it would be o.k. to top off the oil with 10W-30. I didn’t need to add,any oil, but I wanted to be prepared…
My independent shop once put 5W-20 in our 2003 4Runner that is supposed to use 5W-30. It was winter, so I didn’t worry about it–even took a 700 mile trip. It didn’t use any oil for the 5000 miles until it was due for the next oil change.
He said "by" (buy) extra quarts.... :smiley:
Sorry guys, I fixed it.
Wow, @Mike. The year is only half gone and here's your first faux pas.
I’m quite sure it wasn’t my first.