What type of gas do you put in a 1990 Cadillac Seville SLS?
A 1990 Cadillac Seville SLS requires unleaded gasoline. The specific octane rating recommended will be in your owner's manual, but it's likely to be regular unleaded (87 octane) or mid-grade (89 octane). Avoid using premium unleaded (91+ octane) unless specifically recommended, as it won't provide any performance benefit and is unnecessary expense.