[Harvey]

Hum... just a different point of view, but basically the car's done around 25miles with the wrong oil in it.... is it that bad? I'm not saying it doesn't matter, they made a real mess, and it's an idea to try to get the most you can out of their error, but it's not like they'd put coolant in instead of oil.

On such a small run I'd be surprised the wrong viscosity will have do that much damage (75W90 instead of 0W20/5W30).

If you can get a brand new car out of this then go for it... but before doing an engine swap or a car swap for a similar car (that you won't know anything about) I'd negociate to test your car for a month or so (and have a signed paper with all this written down) and then decide after if you want to swap or not. If you're car feels fine, performs fine, consumption is fine, oil/water is clean, temps are fine, ... then I'd just "forget about it" rather than messing around with an engine swap.

Please don't flame me for this! It's just my first reaction when I read your post...