I need some hints - does this sound like a head gasket issue?

suddenly high oil consumption (0,5liter/1000km - about 1qt/620mi) but no smoke from tailpipe. oil consumption before was 0,5liter/4000km

dissapearing coolant but no visible leaks (coolant in reservoir is clear)

low MPG - 18, before it was usually around 21.

All these sympoms appeared after a hard winter.

TIA

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1987 300E 185k miles