mixing motor oils of different weight

Jul 10, 2007
12,041
3
0
i don't know what the garage put in and now i have to top it off.
it should be either 5w-20 or 5w-30, mobil1 full synthetic.
is it ok if i choose the wrong one?
 

PingSpike

Lifer
Feb 25, 2004
21,755
599
126
I'm not a good person to ask, but I personally don't see how you could really screw anything up even if you used the wrong answer here. Surely, different weights and types of oils are mixed all the time due to the residue in the engine.
 

sdifox

No Lifer
Sep 30, 2005
99,095
17,444
126
Originally posted by: BlahBlahYouToo
Originally posted by: sdifox
call the garage?

it was a few months ago.
regardless, id oubt they'd remember.

Odds are you are fine which ever you pick. Most garage have a standard oil they put in, even for synthetic, so it should be that one unless you asked for something else, which you would hopefully remember asking.
 

StageLeft

No Lifer
Sep 29, 2000
70,150
5
0
I assume that one will float above the other but if both are fine for your car you'd just disproportionately use the one at the bottom, and in reality this would be a negligible effect, assuming they really do separate meaningfully in the shaking, vibrating oil pan.
 

bruceb

Diamond Member
Aug 20, 2004
8,874
111
106
Both of those weights are very close and unless you live in Alaska where it will get really cold, either will be fine.
Just open the hood and look at your Oil Fill Cap ... most cars list the suggested oil on there. Use that or the 5W20
unless you are in very hot climate, then the 5W30 might be a better choice. And don't worry about mixing them.
They will work fine together.
 

LTC8K6

Lifer
Mar 10, 2004
28,520
1,575
126
Yeah, it's printed under the hood somewhere. On the cap, or on a factory sticker.

The oil change place should also have put a sticker somewhere. On the door/jamb, corner of the windshield, etc.

But it doesn't really matter, go ahead and top it off with either one.
 

evident

Lifer
Apr 5, 2005
12,100
713
126
i recently mixed 4 qts of 0w20 with .5 qt of 5w20. don't think it will make a difference.
 

Apex

Diamond Member
Oct 11, 1999
6,511
1
71
www.gotapex.com
Originally posted by: BlahBlahYouToo
i don't know what the garage put in and now i have to top it off.
it should be either 5w-20 or 5w-30, mobil1 full synthetic.
is it ok if i choose the wrong one?

Either one is fine. Mobile 1's 5w20 and 5w30 are almost identical in true weight (in other words, one is on the very very thick end of the 20w scale, while the other is on the very light end of the 30w scale).
 

SparkyJJO

Lifer
May 16, 2002
13,357
7
81
Originally posted by: Skoorb
I assume that one will float above the other but if both are fine for your car you'd just disproportionately use the one at the bottom, and in reality this would be a negligible effect, assuming they really do separate meaningfully in the shaking, vibrating oil pan.

Actually they'd mix together, so mixing 5w-20 and 5w-30 would get you somewhere in between there, depending on what the ratios are.