I apologize if it's a stupid question. I ask this because I just took a 6 hour trip recently averaging between 80-90 mph (3200-4000 rpms) and afterwards, my oil level was about 1/8 of inch higher on the dipstick than before the trip. Whats more, since that trip, my gas mileage *increased* noticeably. For example, my commute to work is about 18 miles and I averaged about 30 mpg before the trip and now I average about 31.5 mpg. The increase in gas mileage is not completely surprising considering that my engine is still probably breaking in with about 8000 miles on it. I only mention it because I observed a noticeable jump after the rise in oil level. So the questions I have are: 1. Could my oil have thinned and "expanded" causing it to sit higher on the dipstick and causing the gain in gas mileage? I'm using Castrol GTX 5w-30 2. Could I have a coolant leak? I don't think I have a coolant leak because the coolant level is stable and my oil is crystal clear (I heard it is suppose to darken if coolant is getting into the oil) with about 1200 miles on it. But I'm open to other thoughts about this. Oh yeah, one more thing, I noticed that my oil level sat a little higher after about 600 miles after my last oil change too. Any gurus have insights for me? Thanks.