has 2.2L F2 (non-turbo) engine. the manual is unavailable, ive checked some mazda forums and some people are using 5w40, some 10w30, and so on, generally a 30 or 40-weight. the car uses a little oil but not too bad, and has 164k miles on it. can anyone recommend a good brand and viscosity for this engine? (kinda looking for the reasoning behind your choice also) thanks!