I own a '85 380SE, and was wondering if someone could tell me what the minimum grade gas I could use would be? The manual is not clear, so I have been running the highest all along...just to be safe. But, that is getting really expensive with the current gas prices!! I know the higher grade the better gas mileage I get, but I would like the option to run lower if possible. I have 87, 89, or 91 to choose from where I live. So, would 87 be safe?? Thanks so much for your input anyone!!