if you use 5w40 after 5w30 can you go back?

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Hello! I drive KIA Ceed 1.4 MPI, and alowed oil viscosities by the user manual are: 5w30, 0w40, 5w40, depending on climate.

So, I plan to use 5w30 (or 0w40) on colder months, and 5w40 at summer.

But I heard, once you switch to thicker oil (from 5w30 to 5w40) you can not go back to thinner (from 5w40 to 5w30). Any truth about that? Thanks
 
True!
I am at this point running 500w-1200 in my thirty year old car as I always prefer switching to a thicker oil during summer. ;-)

Joking aside, there is no scientific background to that.
The viscosity choice you made (5w30 in winter, 5w40 in summer) seems very fitting and should work perfectly fine.
 
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Originally Posted by Polyalphaolefin

But I heard, once you switch to thicker oil (from 5w30 to 5w40) you can not go back to thinner (from 5w40 to 5w30). Any truth about that? Thanks



No truth involved. Whoever told you that is....shall we say, misinformed.
 
I used traveller 10w30 Dino in a 85 Chevy caprice wagon 305v8 that always got 20w50. It runs better on the thinner weight and puts more power out. However it does seem to leak more. Car has over 400k miles.
 
Originally Posted by mpack88
I used traveller 10w30 Dino in a 85 Chevy caprice wagon 305v8 that always got 20w50. It runs better on the thinner weight and puts more power out. However it does seem to leak more. Car has over 400k miles.

Holy carp! How many camshafts, carburetor rebuilds, and sets of valve seals did it take to go that far? (Might be able to tell I've had a few pre-EFI Chevy SBs)
crazy.gif
 
Originally Posted by Polyalphaolefin
I heard, once you switch to thicker oil (from 5w30 to 5w40) you can not go back to thinner (from 5w40 to 5w30). Any truth about that? Thanks


No. I went from 0w20 to 5w20 to 5w40 and back to 0w20 recently. No issues. The engine doesn't care.
 
Originally Posted by Polyalphaolefin
Hello! I drive KIA Ceed 1.4 MPI, and alowed oil viscosities by the user manual are: 5w30, 0w40, 5w40, depending on climate.

So, I plan to use 5w30 (or 0w40) on colder months, and 5w40 at summer.

But I heard, once you switch to thicker oil (from 5w30 to 5w40) you can not go back to thinner (from 5w40 to 5w30). Any truth about that? Thanks

No, no truth whatsoever. And it sounds like a solid plan. But remember, once you go thick you may never go back!...‚
 
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Originally Posted by Malo83
PP 5w30 year round in my 2.0T, no need for musical oils.
lol.gif


The OP could just run a thick, +11/+12cSt Xw30 year round and not have to do the musical oils.... I know he's in the EU but the Havoline 5/30 HiMi SB I run from time to time is a 11.8cSt lube.

"But what about CAFE"...meh, never heard of her!...‚
 
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