Car is currently using 15w 50 but i cant seem to find that weight anywhere. I was thinking of using 10w 40 what do you guys think. Car has a rebuilt motor so it is not stock. I am not to sure on bearing clearances, and i cant get in touch with the previous owner. Car has billet mains, stock crank, reconditioned rods, trw forged pistons, billet hydraulic roller cam, gn1 heads, te45a turbo with all supporting mods. What is a good choice in oil weight for this combination. Also does thicker weight oil have effects on the turbo bearing and seals ? Thanks