While I am a firm believer in synth, I personally wouldn't put it in a high millage e30, especially that thin a viscosity Jay, I would bet the valve stem seals would start leaking along with the rear main seal eventually, especially with mobil 1 since it tends to be a very high detergent oil. Just my thoughts.
My recommendation is Castrol GTX 20w50 for summer, 10w40 spring/fall, 5w30 Jan/Feb
But if you are going to use mobil 1 synth, I would use 0w-40 or 15w-40(in summer)
BTW Welcome to the forum