Specifying Short versus Long OCI

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Feb 21, 2008
French Island
Hi Dear BITOGers ;\) , First time poster here. I have been lurking around for awhile. First came to this forum because I wanted to know why the “stuff” goes in the “thing” in gold color but comes out black. I have always got a question in my mind that I know have not been discussed to any details recently in the forum. Would doing 2 oil changes for shorter OCI with cheaper oil achieve better results in magnitude of wears than 1 oil change with normal OCI with the expensive oil, especially in a high mileage vehicle? I know people are screaming about too many variables, so here are some assumptions for discussion proposes. I believe these assumptions are quite common so more people can relate to them. - The car is a Civic with NA engine with 200,000 miles. - The cheaper oil is some Mobil semi-syn that costs exactly half of the Mobil 1, both 5W30 and SM, GF-4 rated. - 2 drains of the semi-syn at 3000 miles OCI or 1 drain of the M1 at 6000 miles OCI. So both options cost exactly the same. Some people will incur high labour costs with 2 drains if they don’t DIY. - 3000 miles in 3 months, 6000 miles in 6 months. - All other conditions are general and average, e.g. for driving style, weather, temperature, 50/50 city/highway. It is expected that a car with high mileage will have some minimal fuel dilution, coolant leak, air filtration system not as tight as it used to be so some abrasive wears. However small they may be, these contaminations and air particles induced wears still exist. Consequently, wouldn’t doing 2 drains short, getting these “bad things” out more frequently, better than 1 drain long?
WELCOME! Some people will say that oil and filters need to be in use a little while to reap its full benefits and changing too soon will do more harm than good. With that in mind the 6 month 6,000 miles with the Mobil 1 would be the better deal. IMO 2 3000 mile changes with the cheaper SM, GF-4 rated oil would be better, especially if the car sees a lot of short trips. Cleaner oil and a fresh filter can't be bad. JMO, Frank D
Personally, I would go for the 6 month option. Less work for you, and the oil should still be well in spec after 6month 6k miles. Civic NA 4cyls known to be very easy on oil. Have you considered 1 year Amsoil route?
I haven't considered Amsoil. My point is in some applications where a cheaper oil is allowing for the same level of wears as an expensive one, frequent oil changes give extra benefit when the shorten OCI is justified by cost.
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