dr bob

Original cosmoline was parafin-based with a light solvent added. It was sprayed on hot, cooled and hardened in place. Over time the parafin oxidizes and turns dark; originally it was translucent clear to pale white.

It was not originally itended as a direct corrosion preventer, only to reduce the damage from impacts from rocks and road debris that would otherwise breach the paint and allow corrosion to start. Coverage on the bottom of the 928 is spotty and seems to vary according to manufacturing day of week and who was forced into the application duty.

Acetone NEVER gets used where it might contact nearby rubber bits if at all possible. As mentioned, it damages paint, and a lot faster than it softens the cosmoline so another negative vote. Mineral spirits/paint thinner works sort of, but it takes time and brushing. I use a stiff-bristle nylon parts-cleaning brush, and get the deoderized paint thinner at the Home Depot. Heavy rubber gloves, sacrificial clothes or maybe a plastic apron, and glasses. Havent tried diesel fuel because of the particular fragrance it shares. Regardless of what solvent you use, follow it up with a good detergent wash and rinse to avoid ongoing stink.

Steam cleaning takes cosmoline off nicely.

Petza914

Anyone tried brake cleaner? That has removed stuff for me that nothing else would tackle.

dr bob

Brake cleaner these days is almost all acetone. Ok so long as you keep it completely away from rubber, plastic and paint. So OK for getting the cosmoline off the rear crossmember and the front suspension arms, but only after all the rubber parts have been removed. Rset of the car, like tub/wheelwells/etc, not the right choice.

17prospective buyer

Brake cleaner here is just aerosolized alcohol. The Cosmoline application on Porsche's does seem to be spotty, with engine blocks being covered sometimes and other times nothing at all. Bob that's my attraction to the stuff, it's wax base that turns hard is what seals better than anything. Traditional oily undercoating merely slows rust down, i'd rather attempt to nearly halt it with a thick layer of Cosmoline.

Diesel fuel seems to eventually dissolve any hydrocarbon, not as volatile as gasoline, lower down the fractional pole/vapor pressure so it sticks to the part being cleaned. It's a medium/transporter for the hydrocarbon you are trying to remove, which then gets rinsed off with more volatile solvents that do not leave a residue (alcohol (brake cleaner) or acetone).

siscogts

I tried Yesterday night with something called White petrol, that is the "fuel" used in cig lighter like Zippos..... Drying time not so fast, very effective if you want to remove cosmoline, but I stayedaway from the cosmoline spots near rubber parts like bushings etc. as I don 't know if this White petrol can be corrosive for them.

Dave928S

Similar to or the same as 'narrow cut kerosene', which is a more refined kerosene with much less odour than 'normal' kerosene. I use it in my parts washer, because it's not too volatile/flammable, and it's great for cosmoline.