MTFCA Forum

I almost posted this question on one of the other two oil threads going, but I don't want to hijack them.

I use Shell Rotella 30 W. After 500 miles when I change it, it is nasty, dirty black. It seems to me that the oil itself should still be good, it just has contaminants in it.

Could I put the used oil in a container with a pump and regular car filter and then filter the dirty oil through the oil filter and come up with used oil clean enough to reuse in my T?

This will not answer your question on filtration, but may still be of help. I suspect that like most, your engine is not rebuilt and has lots of carbon bits and dirt inside the crank case. As I mentioned on another oil post, removing the inspection pan, taking out the horseshoe retainers and then wiping down the entire interior of the engine thoroughly, particularly any horizontal cast boss plus (and especially) the lip of the pan where the horseshoes fit, will be an immense aid in keeping the oil clean. After doing this to an as-is car, I find that 500 miles and the oil is still fairly clear. Before cleaning, less than 200 miles and the oil is black. The "black" is primarily from carbon coming off from under the pistons. Oil burns/carburizes and then falls off the underside of the pistons in sharp shards...this is the black crusty stuff you will be removing when/if you wipe down.

FWIW

I’m going to side with Tom on this as the oil after 500 miles is just dirty and not “worn out”,(the long chain hydrocarbons molecules break down and you lose film strength EVENTUALLY) as in Steve’s position

Tom...the same notion occurred to me and I think I might rig up something to try it, using an old, but functional oil pump from an F100.

I've had my engine all the way apart however, and it has been thoroughly cleaned, inside and out, so I'll be curious to see if the oil gets filthy as quick as 500 miles. My plan is to get it installed and running in the next few weeks.

Use to could buy recycled oil at most auto parts stores. My Father in Law ran a service station for many years and routinely had a oil truck pickup the used oil. Haven’t thought about it in many years but not sure you can still get it sold as recycled oil.

Both trains of thought apply here. Yes, the oil is just dirty. The chemical bonds won't break down in 500 miles. No, used oil from modern cars is worn out even though it may look cleaner. I may be looking at it wrong, but I have better things to do than wash 2.50 a quart oil so I'll just change it regularly.

Andy

John - You reminded me of something. I grew up in a suburb of Chicago in the '40's and '50's, and I mention that because what I just remembered is from a very long time ago, so may be pretty much meaningless in this day & age what with modern chemistry and all, however:

Our next door neighbor in Franklin Park, Illinois was a man who owned and operated a motor oil re-refining business in nearby Schiller Park. A partner in that business with him was his nephew, a chemist, a very knowledgable young man who was also a pretty good mechanic. He and I got to be pretty good friends, but I lost track of him many, many years ago. Because his main function in the business was as a chemist, I paid particular attention to things he told me, one of which I thought at the time was very interesting. He said that there were a number of large transportation "fleets", such as Greyhound, that used, and actually preferred "re-refined" motor oil. In fact, he said that at that time, the only oil that Greyhound used was "re-refined" oil. He said that re-refined oil had a particular quality that new motor oil did not have, that Greyhound and other trucking companies and such, found to be very desirable. All I can remember is that he said that re-refined oil was "tempered". I never did know exactly what he meant by that, but I thought (and still do) that it was an "interesting" remark, and I always thought that there must be something to it, because their used oil "re-refining" business was obviously very successful. (???) FWIW,.....harold

Scott Conger - WOW! What a great article! I was typing at the same time you (and Andy) were. I'll be reading that article very carefully as it will probably touch upon what I was (remembering) and talking about,...thanks so much for posting that Scott,.....harold

Scott - That WAS a very interesting article! Nothing about the term "tempered", but I do now see the obvious reason that large fleets like Greyhound used "re-refined" oil,....pretty much the main reason was probably just "to save money"! Thanks again for the post Scott,.....harold

Tom,
A coworker of mine had been assigned the task to determine what the oil change interval would be on a new engine design. To give a very brief summary he found that carbon particulates are abrasive and smaller than oil molecules and can't be filtered out. A rich fuel mixture was found to be the contributor. The oil change interval was determined by the number of engine run hours to reach a predetermined carbon particulate level.
I wonder if you may have an over rich fuel mixture causing the oil to look dirty? You may be able to look at your spark plugs to get an idea of how the fuel mixture is running. There's several online pics of how to read spark plugs.

David - What Steve Jelf says is true,.... about the fact that when you get old enough (like me) everything somebody says reminds you of "SOMETHING". Your post reminds me of something that I think you have come very close to explaining in your post,....probably the main reason that many automotive engines that have been converted to run on LPG instead of gasoline, routinely go much, much farther that gasoline burning engines. I think the best quality of LPG is the fact that it burns so clean and produces little if any of the (abrasive) carbon particles you speak of!

Harold

my pleasure...glad you enjoyed

Is there any truth to the story that as engine white metal bearings wear they cause darkness to the oil?
I have seen badly worn aluminium thrust washers in torque converters that caused the red ATF turn black
Alan