What the op is trying to say is to drain and top off frequently to keep 75% fresh oil vs. letting the oil go from 100% to 0% at change interval.

Yes I agree a constant 75% fresh fluid > 100-0%

On bravo drive change intervals I think everyone drains and refills before recommended service interval and probably changes it at more than half life

Hello, I work on a tanker we have (2) 8000hp wartsila 12v32 diesel engines we add new oil to keep are TBN # at the correct level. sump holds 750 gallons we add 75 gallons new oil, this is with a purifier. So i see what your your saying John

If there was a oil filter setup on the drive that would be a different story. When I drain dirty oil out of a drive and I feel sick because that dirty oil is protecting my drive which is wrong. I just trying to come up with a way to keep the oil at the highest level of protection with the least amount of hassle. I run 30 to 50 hours on my Volvo drives and have been doing this for a while. The Volvos use the same oil as the engines and now the oil looks almost new all the time and take 5 minutes to do it! I do put fresh oil in at the end of the year, but no longer do I have dirty oil coming out of the drives.

I cannot see what makes only the old/dirty oil get removed.
Just because you topped off with fresh, why is it just the oldest dirtiest at the bottom getting removed.
If you never rotated the drive, there would be no MIXING action.
You may be improving the concentration level off additives and be removing a percentage of dirt, but to think only the old dirty is getting out does not make sense.
Maybe the heaviest metal shavings sink just prior to pulling the plug, but the rest of the oil (old AND new) is going to homogenize. The drive gets rotated, oil gets moved around, old and new combine.
You might be able to maintain an oil mix with less contamination and more additives than what the entirely old batch is just prior to the draining, but at a point you will have diluted the mix past that and the small portion of top off new is not going to restore enough.
MAYBE... you could do this for say (hypothetically and just for sake of conversation #s) 40-50 hours instead of changing ALL at 20-25 before you get the MIX to the point of the constantly used oil's life. But to think you could do this on an ongoing basis and not have the oil suffer sounds incorrect. There will be a point where a larger portion of the oil in the drive has more than the benchmark 20-25 hours on it and the addition of the top off is not great enough to raise the mean or median age of the overall mix.
Unless I am unaware of some method that can be used to keep the old on the bottom, new on top, and no mixing.

What if you only wipe a 1/4 of your... Never mind! ::hitfan:

I like this thread:D

"Never Change your Drive Lube and your Driver will last for EVER!!!!"

I once had part in a test using only the oils rendered and refined from the labia's of virgin Ugandan princesses as drive lube.We all thought we had a real winner and would soon take over the entire lube market. The end results however were disappointingly no better than current Mercury drive lube offerings. The only true benefit turned out to be an incessant moaning if overfilled.

On a lighter note, none of the Labia Lube testing had an adverse effect on our drivers.

Zoogoo you are really passionate about this subject! I'm trying to figure out what it is you're selling ☺

Redline 5W-30 ?

Nope not selling a thing or promoting a product. I have a unique business, I buy and sell manufacturing equipment and machine shop equipment. I get to talk with a lot of engineers from a many different industries. I 'm always in medical labs, aerospace shops, prototype labs, SMT labs, food industry, custom car shops, military, and general fab shop. I used to know an engineer with the Mobil One Lubrication division and had many conversations about different oils and uses and he agreed that the replacing oil as it starts to become dirty is used in many industries today and a good practice. I've used it and like what my eyes can see as to the difference in the oil every remove and replace session.