Engine oil: 0w-20, any reputable brand like zic, shell, total, mobil 1, valvoline, liquimoly, amsoil and kendall etc
for warranty, stick to suzuki 0w-20
Where to purchase: please choose one, will tell you from where you can get that
(Btw I'm using amsoil 0w-20, In lhr, express lube have amsoil)
Regarding scratches, please attach pics, will recommend the product accordingly