petrol in oil?

[unfazed]

[quote author=unfazed link=topic=8389.msg82761#msg82761 date=1371744868]
[quote author=darrsi link=topic=8389.msg82658#msg82658 date=1371686870]
10w/40 is 10w/40 

Not true :rolleyes
The are 3 basic types of 10/40 oil
Mineral 10/40
Semi Synthetic 10/40
Synthetic 10/40
Neither should be mixed with each other, whereas you may top up semi synthetic with fully synthetic and fully synthetic with semi synthetic, under no circumstances should mineral oil be mixed with fully synthetic of semi synthetic.
As I said the specification should match before you decide to mix
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10w/40 is 10w/40, sure, there is mineral based oil and synthetic ester based oil, but there's no ill symptoms of mixing them, and you'll find that even most "Semi-Synthetic" and "Fully Synthetic" oils are already diluted with upto 20% standard mineral oil anyway!

There was an article by the Chief of R&D at Silkolene/Fuchs a few years ago which highlighted exactly this.
[/quote]
May have been the case a few years ago, but Castrol say differently now with the newer spec high performance oils. They do not say you can't they say you should not. It is not the recommended thing to do.
A bit like driving the wrong way up a one way street, you can, but you should not :lol