40+ years ago I used cosmoline for rust prevention on several Toyota Landcruisers. It works but it's a PITA to apply. I have good luck with Fluid film and LPS3. And they're much easier to apply. Interesting enough Lanolin (also goes by Wool Wax) is popular in Australia for rust proofing.

 

Cleaned a lot of cosmoline off machined large factory parts, 24 foot press shafts, large gearboxes, and parts. Was a messy and tedious process.
Would not willingly apply cosmoline to something I own.

An example of problem with persistant corrosion preventatives is cleaning the parts/areas it will be applied to. If surface preparation has any fault the coating may actually mask damage existing or developing underneath. Discovered this trouble with the old Ziebart rust coatings, masking rust due to moisture penetration at parts edges. KM

 

Cosmoline is great for bare steel & Iron (like freshly-machined engine blocks) to prevent flash-rusting during storage or shipping.

But for the undercarriage of a vehicle, the correct product is "rubberized undercoating".

(phone app link)


(phone app link)


(phone app link)

 

@Steve83 thanks for the reply. I spoke to a guy that details many cars and trucks for the local dealerships. He uses this 3M product https://www.3m.com/3M/en_US/company-...2638249&rt=rud

He'll undercoat most ferrous metal components underneath. $275 to do the job. Any rusted areas he says they'll neutralize before coating. I trust him, he details my Wife's car as well as other ppl at my business.