98 V70xc - Accidentally put in 10 quarts of oil and drove

[erikv11]

... Temperature stayed in the normal range and heat blew hot, but there seemed to be abnormally high coolant pressure - when I parked the reservoir cap was hissing and radiator inlet hose was noticeably less squishy than normal. ...

So other than running a compression test and changing the oil filter, what should I do now? ...

Is there any oil in the coolant?

You can rationalize the firm hoses but that hissing is not normal, worth following up on. I would check the coolant for exhaust gases too, just to cover all the bases on the blown-head-gasket front.

[Ou2mame]

Yeah that's what I was thinking. Subarus are known to dump exhaust into the coolant system and the first sign is an over pressurized coolant hose.