should i use synthetic and premium gas in my 1992 cadillac brougham?

[livelifetothefullest]

i just bought a 1992 cadillac brougham 350 5.7l v8 and was wondering what do u guys think i should use? i looked inside the valve covers and it has a tiny bit of baked on oil inside but i can see all the metal parts so its not that bad so i was thinkin if i use synthetic oil it will remove that baked on oil and clean the engine real good? the car has only had regular oil put in it like 5w-30 when i bought it .but its due for a oil change soon so should i just go with 10w-30 mobil clean 500 or 7500? im in chicago and temps can go down to 20f.also will i clean more stuff using premium gas because my car is fuel injected? the manual recommends 87 unleaded.

 

[rtkskater44]

synthetic and premium is the way to go. i run that through my altima which is 87 recommended and it idles smoother and runs cleaner. much much cleaner. my muffler doesnt turn black as often now