Trialed OT8 and BIO TA this week on synthetic oil on Concrete Block Paving and Tarmac. The oil has been down a while (approx 3 months).
With the BP there was still slight shadowing even after 3 applications but it was probably as good as it was going to get after the time it's been down. With the tarmac the oil lifted at the first attemp but the mark remained, as expected.
I would say a good product but a bit pricey.
I'm sure they'll send you a litre of each for trial purposes if you drop them a line, although we got ours from from a local supplier.