I guess I'm mistaken then, but I could have sworn there have been multiple threads on this site about oil and oil changes, stating that 7500 miles is about the time the filter should be replaced. I know Xtremerevolution (the self proclaimed "duke of oil") who seems to know his stuff when it comes to oil, has stated this several times and he is all for extended oil change intervals. I usually let mine go about 8000 miles and then I have it changed along with the oil. Very interesting to see how many different opinions there are on this subject.
The 7500 mile number was in reference to the gasoline engine. Note which section of the forum this thread is in. The byproducts of gasoline fuel differ greatly from the byproducts of diesel fuel. Furthermore, a filter change in the gasoline Cruze requires nothing more than unscrewing a cap and removing a filter, which by the way will not be dripping with oil unless you just turned the car off. It is a 2 minute procedure and doesn't even require topping off the oil level.
Note: the "duke of oil" reference was a title given to me by other moderators. None of the little purple titles are assigned by their owners; they are given by other members.
I support extended oil change intervals on the basis of being economical, environmentally friendly, and reducing engine wear. Trending oil analysis has shown that most engine wear occurs in the first few thousand miles after an oil change, after which it begins to drop off. It is not a linear increase. As a huge benefit, it is far more convenient to change oil at 15,000 miles instead of 7,500 miles.
Agreed. But Diesel is the outlier here. 95% of the people that will read his posts (especially the ones who just come to the site for certain questions/answers) on oil life will see the 15,000 mile interval he is using and think they can do the same (not knowing his full history). I don't want to get into a whole big thing here and I have no doubt his oil and filter are just fine after all those miles as his driving patterns are nothing like the majority of the CTD owners out there. I put 26k on my first year of ownership and thought that was a lot of driving. I had the oil changed 4 times. I guess what I'm trying to say is that the information that he supplies is priceless, but we need to be careful when talking about things that clearly would only apply to his driving habits. Oil analysis is great, but going off your point (and current driving patterns) his analysis at 15k would look a lot different than yours at 15k. Just don't want to confuse people.
He is an outlier only in the sense that he puts on a lot of miles in a short period. His actual driving conditions do not differ all that significantly from everyone else's. You need to remember that diesel engines are far easier on oil than gasoline engines are. The EGTs are much, much lower, which is why your turbo is only oil cooled. The heat simply isn't an issue. The engine generally runs oil cooler than a gasoline engine does, and contaminants from the combustion of diesel fuel are much
less acidic than that of gasoline fuel. As a result, 15,000 mile oil drain intervals on a synthetic oil are very easy to achieve.
I'll wager half the cost of an OAI oil analysis that your oil analysis report won't look all that different from his.