I know everyone says to only use synthetic oil but I have only ever used semi synthetic. Am I doing anything bad to my motor by using that versus full synthetic or even plain old conventional?

 

No. You might be losing 0.2MPG but otherwise no. Just keep it changed on schedule and you're good to go.

 

You could even use conventional oil to save some money and you'll still be fine. Synthetic or Semi is good for high end super powerful cars but for daily drivers and for cars that you dont track or beat on....conventional is perfectly fine as long as you change it on a regular schedule (3K or 3 months).

 

Non turbo, use conventional or semi blend.



Turbo applications should always use synthetic.