- Joined
- Feb 6, 2010
- Location
- hopatcong, nj
i have a 1999 200hp evenrude fitch engine. what lower unit oil should be used? i used castrol full synthetic oil that was rated as gl-5 which is used in automotive applications. i have heard the marine rating is ussually gl-4. the diffrence is that the gl-5 has more sulfur in it which make some metals corrode faster like coper. was wondering if gl-5 is bad for my lower unit and should i drain it for gl-4 rated gear oil? please dont respond with a guess. i'm looking for answers from people that really know the science, an expert. thank you. was hoping to find a tech or owner of a marinia that really knows the facts and science behind it, not just a boat owner telling me what he does. with boat people many always say go to the dealer and buy the manufacurers oil but do we do that with our trucks? no we dont. if we own a dodge do we just buy mopar oil, or ford just motorcraft oil? i'm sure most of us would say no.