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Re: Oil change intervals and warm and fuzzy feeling Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Fri, 23 May 2008 06:58:03
In Reply to: Oil change intervals and warm and fuzzy feeling, J, Fri, 23 May 2008 06:32:35 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Good points. I assume that your engine has considerable miles by now (in excess of 120K). Wear and damage due to degraded and dirty oil doesn't show up at 40K; it shows up over 100K.
The fact that you're doing oil analysis is providing you with a level of protection. Extended oil changes are fine in the case where the oil is of good quality, the extension doesn't go too far extended, AND there are no underlying engine issues. For example, if an engine has a little blow-by and the hot combustion gas is degrading the oil faster, 15K may be too much. Or if a bearing had a production or installation issue and was wearing a bit faster, or a seal was leaking a little coolant into the oil, then the extended oil change interval could be a problem.
So doing an extended (I call 15K extended) oil change, but with the added protection of regular oil sampling and analysis, is reasonable. I'd worry about doing the oil sampling/analysis at 15K intervals, because a problem that starts to develop at 7K miles has another 8K miles to propagate.
In defense of shorter intervals, not all of us are doing oil analysis. And again, oil analysis at 15K miles may only tell you that a problem has already occurred. Also, the fact that your engine hasn't blown up is excellent, but a sample of one doesn't statistically prove the interval is OK. It is a good data point.
If it matters any, my '97 9K was originally a lease car. It was turned in at 45K miles, and the second owner (I'm the third) had the engine sludge at 48K miles. New engine (and $5K). So it is possible that the oil was never changed in those 45K miles, but I'm going to assume the engine had the oil changed at least every 15K, possibly the 10K the Saab required. So that's a sample of one that didn't fare well. Since that new engine, the second owner, and now me, change the oil every 5K.
I will take offense at the idea that folks that do frequent oil changes bury the oil in the backyard. Burying oil in the backyard at 15K mile interval is equally unacceptable as 5K miles. I carefully capture all of my used oil and bring it in for recycling.
In the late '90s many car companies started going to extended oil change intervals of 7.5K and 10K. About the same time many car companies (Saab and Toyota come to mind, but others, also) started having oil sludge issues. Hilarity and class-action lawsuits ensued. I'm sure there is no relationship between the the extended changes and sludging.
Anything with cars is a probability, and it takes a larger population to make definitive statements. Lightning doesn't strike often, but if it's you, it's a bad day. I find changing the oil more frequently (I've settled on 5K) provides a level of security, yes. It also provides protection against other faults in the engine that might be starting.
posted by 192.249....
, Fri, 23 May 2008 09:56:36, Fri, 23 May 2008 06:58:03 <-- Viewing This Message
, Fri, 23 May 2008 09:04:06, Fri, 23 May 2008 13:03:53, Fri, 23 May 2008 13:02:31
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