In the 40s is OK but why?
If you've bought new, you're still in the heavy depreciation part of the residual value curve (sounds technical, no?) so where is the break point you say?
Depends on alot of things.....what your model's worth, the market for it, new models, your loan structure (if you have one) etc.
That aside, 40K is not a bad idea.
Age is also a factor.
I offloaded at just about 60k, and 2.5 years old from new, thus avoiding cambelt.
Amazingly got 75% of what i paid for it (the capital cost).
(mods added up to about ?1k which i haven't taken for in that assessment)