Hi I just bought a 2015 smart fortwo the other day with 21,000 miles on it. I was checking underneath and checked the tranny fluid saw it was a little low, so I decided to change it all. So I went to the auto parts store and got mobil 1 sythetic gear lube 75w90 API GL-5. Changed it with proper level. Drove car and it drove great smooth shifting and everything, drove about 50 miles with the new oil. I had it in the car almost a whole 24 hours. The next day I read online that GL-5 is not what the car calls for, so I went to the store to look for something that had a API GL-4 rating. All I could find was Royal Purple max gear 75w90 that says it meets and exceeds gl4 and gl5.... so the question is, did I just screw myself?? Or am I ok? Is my transmission going to be messed up now? Or am I safe?? Please help I am worried that I might need to replace the tranny soon ?