So I just bought it and trying to figure out whether I should use 5w20 semi synthetic that came with the vehicle or just use conventional 5w20. It's a 4cyl with 106k miles. Unfortunately I don't have any maintenance records. It is a one owner vehicle that I bought from someone that basically flipped it. Engine looks bone dry from what I can tell. I just don't want to create problems down the line with seals leaking/weeping. Any thoughts?