GolfGTIforum.co.uk

General => The garage => Topic started by: the_stink on 05 June 2011, 14:46

Title: is it ok to mix 0w -30 with 5w -30?
Post by: the_stink on 05 June 2011, 14:46
Need to top the oil up and couldnt find any of the castrol 5w -30

now ive done some searches and the impression i get is that it is ok?
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: rossbarry1 on 05 June 2011, 16:26
oil is oil isnt it. better to have a mixture than none at all   :undecided:
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: Andy! on 05 June 2011, 16:40
Agreed, its not ideal but oil is oil is oil is...
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: AudiA8Quattro on 05 June 2011, 17:15
I would think 5w30 is too thin for an old KR engine, surely 10w40 would be better.
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: Wayne on 05 June 2011, 20:59
I would think 5w30 is too thin for an old KR engine, surely 10w40 would be better.

Spot on :afro: 10/40 semi would be the better choice, 5/30 is way too thin
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: the_stink on 05 June 2011, 21:24
Cool so really 10W40 is what should be in there, I grab some when - get paid and change it out 
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: Wayne on 05 June 2011, 21:33
Cool so really 10W40 is what should be in there, I grab some when - get paid and change it out 

Yep 10/40 will be fine :afro:
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: the_stink on 05 June 2011, 21:50
Would having oil that too thin cause any major probs? Just paranoid now :p its at the corrrect level etc
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: Wayne on 05 June 2011, 21:51
Would having oil that too thin cause any major probs? Just paranoid now :p its at the corrrect level etc

No it will be fine in the short term.
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: AudiA8Quattro on 05 June 2011, 22:24
Would having oil that too thin cause any major probs? Just paranoid now :p its at the corrrect level etc

No it won't cause a problem, except the engine may drink oil as tolerances between parts on old engines aren't as good.
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: the_stink on 05 June 2011, 22:29
Ahh I see, cheers for all th replies guys :)
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: danny_p on 06 June 2011, 22:35
the 0 and 5 parts are fine but wtf are you doing putting  /30w oils in it for ????   they are way to thin when hot
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: the_stink on 06 June 2011, 23:23
the 0 and 5 parts are fine but wtf are you doing putting  /30w oils in it for ????   they are way to thin when hot

when i ordered it from eurocar parts it was one of the oils it said was for the car, typical stink getting it wrong as usual!! well im going to drain that out ASAP and get the 10/40 in think ill have to see if i can borrow some money from someone broke till 17th and i can only assume the longer the oil is in there its not really going to be doing me or the car any good
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: AudiA8Quattro on 07 June 2011, 10:33
the 0 and 5 parts are fine but wtf are you doing putting  /30w oils in it for ????   they are way to thin when hot

Surely it would be worse to have thin oil when the cold? it would probably just fall through the engine.
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: Agreeable Slick on 07 June 2011, 10:38
Cold oil = thick oil.

5W30 would have been ok when it was a new engine, but considering age, it needs something a little thicker now.
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: the_stink on 07 June 2011, 12:16
well there are no leaks, but im grabing some castrol magnatec 10/40w tonight and going to drain the oil an replace it, also will be getting a replacement oil temp sensor on thurs
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: AudiA8Quattro on 07 June 2011, 12:34
Cold oil = thick oil.

5W30 would have been ok when it was a new engine, but considering age, it needs something a little thicker now.

Yes i understand that.
What i meant was when the engine and oil are cold, the tolerances are bigger than when warmed up, so surely a thicker cold oil would be better.
Hence why people use 10w40 instead of 5w40.
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: Agreeable Slick on 07 June 2011, 13:00
The numbers on the bottle are like this: first number is when the engine is cold, and the second when the engine is hot. 10w-40 for example the 10 bit means that the oil must have a certain maximum viscosity/flow at low temperature. The lower the "W" number the better the oils cold temperature/cold start performance. The 40 means that the oil must fall within certain viscosity limits at 100 degC, again the lower the number the better the performance at temp.

Basically when the engine and oil are cold two things happen, engine tolerances open up by a nats knacker, and the oil becomes thicker (read molecules move closer together) so that it cannot pass through the micron thick gaps that open up.
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: AudiA8Quattro on 07 June 2011, 14:55
Well put there Mr.Slick.
But still an old engine will use more oil when warming up, is this not true?
After disconnecting the breather on an old polo i think this must be true, the volume of blow by was much greater when the engine was cold.
Even though oil is thicker when cold, surely this is when you will lose the oil?
Like i said already, this is why people use 10w40 instead of 5w40.
I think we are probably saying the same thing in a roundabout way.
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: Len on 07 June 2011, 15:07
well there are no leaks, but im grabing some castrol magnatec 10/40w tonight and going to drain the oil an replace it, also will be getting a replacement oil temp sensor on thurs

Good choice! :wink:
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: Agreeable Slick on 07 June 2011, 15:12
Well put there Mr.Slick.
But still an old engine will use more oil when warming up, is this not true?
After disconnecting the breather on an old polo i think this must be true, the volume of blow by was much greater when the engine was cold.
Even though oil is thicker when cold, surely this is when you will lose the oil?
Like i said already, this is why people use 10w40 instead of 5w40.
I think we are probably saying the same thing in a roundabout way.

On start up the engine (oil pump) will pressurise the system. This can force some oil past rings etc due to the higher tolerance gaps so aye, as you say the oil can force by and out through a breather.

Fortunately this is minimal as the metal components will heat up quicker than the fluid will, and thus close the tolerances down again.
Title: Re: is it ok to mix 0w -30 with 5w -30?
Post by: the_stink on 07 June 2011, 21:48
well drained the oil the eve and replaced with 10w/40  :smiley: