christ!! mine uses a litre every 1k miles although it is modified a fair bit and i have found that using different brands of oil but staying with 5w40 fully synthetic can vary the amount the car uses by a huge margin!!
Millers competition oil i used last year, the car burned hardly anything, comma oil my car drinks it!!
I would try either MOTUL 300v or silkolene pro S.
10w50 will just help with the heat side of things but id just get a cooler tbh.
Ive got one as i go on track quite a bit and its better to be safe than sorry