Get an oil analysis done by Blackstone Labs. Driving on the same oil (even Mobil 1!) for 18,000 miles is most certainly not good for your engine.
You should be changing oil at least once every 6 months at a minimum regardless of the number of miles. If you drive the car more than 8K miles a year then you probably need to be changing the oil even more frequently than that.
__________________
2011 370Z 6MT Sport Gun Metallic | ARC | CJM | Ecutek | FI | Fujimura | R2C | SPL | Stillen | TWM | Z1 | ZSpeed |
|