How can the formula of WD-40 remain a trade secret? Wikipedia says


  WD-40's formula is a trade secret


How can it remain a secret today? Can't mass spectrometers, NMR and other equipment be used to determine the structure of the compounds that go into it?

To put the value of the secret into perspective, the WD-40 company (whose flagship product is its namesake) makes \$76M a year and is currently worth \$2.7B
"How can it remain secret?". Trivial answer is - it can't (it isn't).

WD40 is a Fast Moving Consumer Good (FMCG). It is also a reasonably cheap product - as an industrial chemist this suggests at least two things to me:


It doesn't contain anything rare or expensive
It isn't difficult to manufacture


As an ex-petroleum chemical analyst, with access to a reasonably complete lab, checks to do :


Get the Safety Data Sheet (below is composite information from a number of WD-40 Penetrant SDS)

cas        %
64742-47-8      50-70    isoparaffins petroleum hydrotreated HFP

64742-56-9      30-35    paraffinic distillate, light, solvent-dewaxed 

61789-86-4      &lt;5       calcium petroleum sulfonate 

111-76-2        1-3      ethylene glycol monobutyl ether 

Not Available    1       fragrance
Check the SDS info using physical/chemical testing
If you have the gear available :
Density
Distillation
FTIR
GC (GC-MS if you have it)
AAS/ICP - metals (ICP multielement would be best)
CHOSNP analysis for hetero atoms
Rebuild the product from data. Check to see if it performs the same.
Improve on the product (believe me - WD-40 is NOT the be all and end all of penetrating oils - technology has improved since its formulation).