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Have been working on my own cars for years, mainly Rover's, Alfa Romeo's and Lancia's. There's one thing though that tends to puzzle me sometimes, and how people rave about it so much, and that's the subject of penetrating fluid. Plus Gas, WD40, Triflow, P Blaster - there's loads of them. I understand the principle of how it works, but what are peoples thoughts on it?

As an example, the rear shock bolts (long) on the Alfa Romeo 156 - probably an extreme example as these are know to be problematic anyway, although my choice of penetrating fluid - P-Blaster or Plus Gas, didn't touch them. Another example from the other day, whilst changing brake hoses on the 156 - the 11mm unions became stuck on the copper brake line. Bring out the Plus Gas, soak them overnight, still completely seized in the morning. Obviously these are quite delicate, so instead of messing about trying to tighten then loosen like I normally do, applied a little heat - no problems undoing them. Trailing arm bolt, no luck with the Plus Gas again, a little heat and out they come.

Obviously there are many scenarios where heat cannot be used to unseize fixings, which is ideally where penetrating fluid takes over - but has anyone really had an success with it?
 

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I've heard some people mention the need for penetrating oil. Not a penetrating fluid like WD-40. I have yet to use a penetrating oil.

I use fluids similar to WD-40. At work they can be useful working on small items with seized bolts. Usually I need a lot of heat to weaken the thread locks and glues that are used on some items I deal with.

At home I tend to use them to remove annoying squeaks from door hinges, or free up window hinges on aluminium joinery.
 

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Plusgas smells so utterly awful that it must be doing something. I think if you have two lumps of metal that are rusted into a solid lump, probably only heat will work. If they just need a bit of encouragement, it can't do any harm.
 

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^
This. When I worked on my cars I used penetrating oil on stubborn nuts and bolts. It worked often enough to be worth trying.
 

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I’ve used them all.

I use WD 40 and soak item days before I intend to work on them. I also used Plusgas in another life.

I use more often than not a mixture of ATF and Acetone. I’ve not done scientific studies and every stud and nut are different, but it’s one of my options.

WD40 is sprayed on anything that stays still long enough on our cars. :)
 

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I'm with TME. I think these things are just a fiendish industry placebo to fool the gullible and the desperate! :D

You *think* (or hope) that they are doing something... but whenever I have finally managed to break the stiction on a reluctant nut, bolt or screw, I can never see any evidence that the penetrant has got anywhere near the sticking/rusted faces. I use Plusgas, WD40, Halfords' Shock-Unlock and their Penetrating spray.. but none is any better or worse than the other, since none of them apparently actually do anything. :D

They do have their uses though, since they encourage you that surely *soon* the offending seized items will separate... and once the thread is apart, a bit of the lube does tend to make it easier to unscrew the remains... a bit like your mate offering to buy a round just after you just bought one.. :D


Ralf S.
 

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WD40 isn't really a penetrating oil, it's no better than a diesel soak. You'll get much better results from a decent PE like PlusGas or Kano, though even these will struggle with a solid rust-blocked thread, for example. Heat will usually win out as it's physically changing the sizes of a joint and releasing it
 

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WD etc is fine for a smooth exit of a mildly rusted bolt or nut.
Heat or angle grinder for the rest.
 
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