For fellow Focus ST (or anything else with a 2.0 or smaller Ecoboost) owners, I just found out the hard way that there's a class action suit going on about the Ecoboost 4s. All I've ever read is they have no head gasket issues and, being a closed-deck block, I figured that, too. Well, I've got about 180k miles on mine, running perfect, start it one morning and it smokes like James Bond's DB5 evading SPECTRE. It had been very slowly losing coolant for a few months, but I figured it was just a small leak somewhere. When it warms up, the burning coolant mostly goes away. Coolant and oil temps always dead steady, no evidence of mixing fluids, no combustion gases in the coolant, otherwise runs perfect. OK, figure it's the turbo coolant seal as I've read people typically get 120-150k out of the turbos. Mechanic does a hydrocarbon test and finds none, so he figures the same thing and replaces the turbo, which was not easy to get quickly with all the shipping delays. Same problem (though, the new turbo spins up quicker), so it goes back to the mechanic. Mechanic scratches head and does some research, finally finding a TSB stating that, if this very problem is observed, to replace the long block—not a head gasket—the whole engine. No mention of cause and I needed to know what that is, so I Googled the TSB number and found a car news article listing two law firms involved in a class action suit about it over Ford concealing this problem (which jives with my lack of finding anything about it and I will be putting my name in for this suit, though the high miles might earn me little sympathy). Go to the firms' pages and they state that the problem is related to some kind of manufacturing issue where grooves in the block or head surface fill with coolant, eventually eating their way to the cylinders. How Ford can't understand how to properly machine a mating surface after well over 100 years (if that's what it is, but that's what it sounds like) beats me. This is about the worst time in car sales history to probably have this problem as even junkers aren't cheap and I can't get away with a junker, anyway. Coolant doesn't seem to be mixing with oil, so I'm going to try the highest rated head gasket sealer to hopefully get another inspection sticker and buy me some time to trade it in (I might get a "beater" in between while waiting for the next car—likely not a Ford and I was seriously looking into replacing this with a Maverick when the time came—to be built and delivered). It's too bad as I loved this car as a daily driver and it had nearly perfect reliability until this. So, if you have something with one of these engines and notice the coolant starting to drop with or without obvious burning, be prepared.