Just approching 100K on a 2005 Pontiac Sunfire 2.2 ecotec, used Valvoline 5w30 all climate from the start. No issues to speak of in the valve train thus far and no leaks. All hiway commuting miles. Question is this; Switch to a semi-sythetic now, or do an oil analysis and see what it shows, or simply stay with what I have been doing? The only real nerve racker I have had since the get go has been the 9018 coffee filter protecting my motor. Any input would be appreciated. Thanks.