Hi your best bet, and thing is what the guys that run the big M90 and 112 do. use turbine oil. ie jet oil. i have 2 liters for my m45 which should last me a life time. i went to my local air field and ask them if they could help. they gave me a bottle of jet engin oil for free. you need some thing that can handle the heat. as we cant fit oil coolers to our setups...
just my 2c