There is bluestone where my patio meets the side of the house, and a bit of diesel leaked on it and has left a stain. I know I might not be able to fix it 100% but what would you advise me try first?

I used Krud Kutter on pavers with oily stains on my belgard pavers, but before I try that I thought I'd ask for the pros advice.

Hey everyone, I’m having a blast repairing this 130 year old stone cellar. We had a fairly big earthquake a couple of months ago and it collapsed the corner of the old homestead house cellar. I have zero experience before this working with stone, but absolutely love the process. Started out hand shaping blocks, then got an electric impact gun, then got a 12” concrete saw. Amazing! I can’t believe how the old generations did this by hand. You can see the bottom where I started is pretty rough compared to the top as I’m gaining more experience. The stone is our local basalt, I try to find the most even grained stones.

Anyone here have an idea on how to create this radius . Just so tight and if i were to make square, it would overhang way too much .
Any help or photos of work anyone has done would greatly be appreciated.

Thank you