Board Thread:Game Discussion/@comment-176.221.120.73-20170621095251/@comment-26829117-20170621113424

You can but it is significantly more expensive than doing it with the Porsche 919 Hybrid (2014). You need to upgrade a car to PR 95 to unlock the 10 lapper I think (even though the PR for the 10 lapper is only PR 86).

As always it depends on your goals. If you upgrade the Audi to get to the 10 lapper then it will cost you 855 and BRL2,331,100. To upgrade the Porsche only requires 258 and BRL269,000. However, the Porsche costs 950 to purchase.

If you aren't aiming for a full garage or 100% completion then the Audi is cheaper. If you are going to buy the Porsche or are aiming for 100% completion then the Porsche will be cheaper.

Whilst the RR3 Wiki:Upgrades Strategy For 100% Completion doesn't directly answer your question it does provide a lot of the background information.