Do you have Seafoam available in stores? If so buy a bottle of Seafoam and remove the spark plugs and pour four ounces into each cylinder and let it drain into the crankcase. This can take a few hours, check with a flashlight to make sure it has drained. Then drive it for at least 30 minutes or up to 100 miles and then change the oil. Then fill up with 20W-50. There are harsher ways of flushing, but for the first time I'd go with Seafoam since it's milder.
2001 Miata LS 5-speed
