Originally Posted By: BrocLuno
It won't hurt a thing and may actually help. As oil is circulated in the engine and experiences heat cycles, it develops unique anti-wear compounds. These are lost at change and you start over. There are some technical white papers covering this subject. Shannow can prolly point you to them ...
Many knowledgeable BITOG'ers do not change the filter at the same interval with the oil, me included. Leaving behind some residual oil leaves some of the already developed beneficial compounds in place.
We usually change the filter every other oil change and usually a month after the oil change. to allow carry over long enough for the new oil to develop some of its own compounds.
The main reason we change oil is to get the TBN back up where it belongs. Putting 75% new oil in will that easily
This is why I only change 13.75 ounces of oil every full moon and using only the illumination of the full moon since we all know motor oil should never be exposed to sunlight. I have found this formula leaves the optimal ratio of these beneficial anti-wear compounds in my oil.
Ideally, its best to use the Aztec calendar, the Tonalpohoalli. But since it is difficult for the non-Aztec cosmologist to decipher, I typically just follow the full moon sequence which approximates two Aztec weeks.
Honestly, I never tire of the bazaar rituals invented and adhered to on BITOG amongst the devout.
And I mean this in a completely good-natured way because I have great admiration and respect for you guys.
To the OP. I appreciate your dilemma living in such a community. I was stuck in such an environment many moons ago and used to change my oil about 3:00 in the morning when all the nosey neighbors were passed out.