I was wondering if anyone could suggest a cleaner to remove some crusted tree sap without damaging my M5's finish/paint. So far, I've used Goo Gone (citrus cleaner) to remove the majority of the sticky goop of the sap. But as I've said before, now all that remains is a hard crust that Goo Gone will not remove.
Find a paint shop in your area with a good reccomendation. Have them look at it before you go any further. You may already be too late. Tree sap should be removed as soon as you see it. Letting it solidify is bad news.