Greenish white makes it definitely suspicious of moisture rather than an oil leak, but I’ll still caution you to think of a worn distributor shaft, possibly aggravated by a vacuum advance leak or back pressure from a plugged PCV system. If this was a rear cam mounted distributor, I’d be cautioning about a worn distributor shaft seal, either an o-ring or the shaft seal itself, as that is very common. Your 1985 is a side mounted distributor off the auxiliary shaft. I had a worn distributor shaft in a 1985 B230F that caused all kinds of problems until finally properly diagnosed, most notably until the engine got hot, but never got to the point of an oil leak that fouled the cap, especially evidence such as you describe. If it's a moisture issue then you can go to town attempting to put dielectric silicone grease around the cap to act as waterproofing, but that really shouldn't be necessary unless you have a great inclination to use a pressure washer under the hood. This is perhaps an absurd thought, but do you have excess vapour out the exhaust to suggest a head gasket leak?
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now