I made an old ale / winter warmer with spices, orange peel, and medium toast American oak chips, a 2.5 gallon batch. OG was 1.083, and Wyeast London Ale brought it to down to 1.010. (9.6% ABV.)
I used .5 oz oak chips during active fermentation, and at 14 days added another .5 oz. I bottled at 21 days.
I've just started to drink it, and I have to say that although I was concerned that the American oak chips would give an overpowering flavor, the opposite is true. I can't really detect much if any oak flavor, and the spices and orange peel flavors are far in the background as well.
I don't know if it's the strength of the beer, or the dominance of the yeast character, but it seems like this beer is just too sturdy for 1 oz of oak chips to set off balance. Maybe if the whole oz was added after fermentation, it would be more noticeable. I can't really say.
It's delicious, by the way.