Should I use a flushing oil before changing to a synthetic?

[GabrielKnight]

I'm planning on moving on to Castrol Edge 0W40 next change.

Car Bible says:

'If you've been driving around with mineral oil in your engine for years, don't switch to synthetic oil without preparation. Synthetic oils have been known to dislodge the baked-on deposits from mineral oils and leave them floating around your engine - not good. It's wise to use a flushing oil first.'

but then condradicts itself saying that flushing all deposits might cause oil to leak from holes previously protected by the baked on deposits.

So, what to do?

[MatBrown]

Just drain and fill, your not running mineral oil anyway.


Mat.

[GabrielKnight]

Is my Magnatec a phoney oil as well then?

[Allan]

its a semi synth....

Now if you flush the engine there is always a chance that you can cause an oil leak so bare that in mind!

Just get the engine warm (not hot) and drain / refill (maybe do the filter depending on when it was last done)

[Purple]

Get a cheapish tin of fully syn oil and run the engine quite hard for a week. After that, drain it out and put in a decent quality fully syn oil for normal long-term running.

[GabrielKnight]

Is it likely I'd get an oil lea from just 67,000 miles. I guess its impossible to say bcos its had a few owners and only one needed to have twatted it.

[pieman]

i'd do what purpel said! using engine flushes can actually
cause more trouble than they are worth not just oil leaks
it can dislodge any shit thats is baked on to your big or
main brearings (crank) which WILL have wear in them
and the flush might bring that wear out! had this happen
to us at work with a misutsubushi F T O! the best and
safest way to clean ur engine is to do some quick oil
changes a couple of hundred miles or so in between
then the last time you change it do ur filter! the oil in
my 3 is as clean as it comes out of the tin and this
is all i have done and shes on one hundred k!