I just realized I've had the Delvac 5W40 in my truck for 5000 miles. Now, I have to tow a 3500lb trailer to Denver (1000+ miles). Then, I'll travel around for another 2K miles. So, I'll have 8000+ miles on it soon. I really don't want to change out the oil. It still looks new, like light brown honey. Should I change it now or go 8K-10K on it? And no, I have no time for a UOA. Thanks in advance.