quote:
Originally posted by deepsquat:
I am sure I could have had very good results had i not changed the filter quit so frequently..but I am not doing an experiment to see how far I can run 5 quarts of oil...I am trying to make my car last...so I try to have clean oil at all times... Yes my oil is clean at almost all times...tell you what..if you think that just changing you filter and topping of is just as good...try it for 30000 miles and let us see YOUR UAO....bet your ## won't hold a candle to mine..
I think one of the points he's trying to make is that to say you have "29500 miles on oil" is deceptive. You might have 29,500 miles on a couple ounces, and 27,000 on a couple, and 24,000 on a couple, and 21,000 on a couple, etc. So assuming the car holds 4 quarts at a time plus 1 quart in the bypass, and that you started off with 5 quarts and swapped out 1 quart 9 times (every 3,000 miles), the AVERAGE time on any given quantity of oil in that engine after 30,000 miles would be 13,389.39 miles. Which makes this a much different oil analysis.
If anyone cares how I got that number, imagine that you have 5 separate quart-sized containers of oil, each with 3,000 miles on it. Now switch out one quart for a quart with 0 miles on it. Now mix the oil all around and you have 5 quarts with an average mileage of 3,000+3,000+3,000+3,000+0 over 5 equals 2,400 miles. Now put another 3,000 miles on each of them. Iterate this nine times (in, say, MS Excel) and you get a final average of 13,389.
What's interesting about this is that the limit of this formula as n goes to infinity is 15,000, i.e. after 500,000 miles, your oil would still have an average of 15,000 miles on it. Obviously draining one quart every 3,000 miles is the same as draining 5 quarts every 15,000 miles, which is why the answer works out the way it does, but it's interesting because the math shows that if your oil could hold out another 1,500 miles without being topped up (and it looks like it would), then in theory you could go on like this perpetually and never do a full drain again, although you would have to keep changing the filter media.
[ July 18, 2003, 02:19 AM: Message edited by: alexiskai ]