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Old school.
I use automatic transmission fluid in the motor - ever see a dirty internal transmission? BUT it depends how you plan to run the motor. On recently purchase used vehicle I run the tranny fluid for about five hundred easy miles before an oil change.
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ATF in the oil to clean the engine works (somewhat), but is also an "old wive's tale".
Yes, there is no sludge in an automatic transmission, but that is because there is no combustion in an automatic transmission.
Transmission fluid is much less viscous than motor oil...especially old and oxidized (sludged-up) motor oil, so naturally it will "cut' it.
The higher solvency-ratio of the ATF is what does the "cleaning", not any kind of detergent-based action.
There are actual oil-based cleaning-agent additives that can be used in the engine that are far more effective than ATF, while still being safe to use. Stay away from kerosene-based cleaners.
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A trick from the trade - use diesel engine oil of the correct grade for the next two oil changes and only run each for 2/3 of the full time/distance.
Deisel engine oil has more effective (aggressive) detergents but will also give full, normal engine protection against wear.
If you still have a build-up then the only way is to scrape clean the rocker covers, remove the sump and scrape that out too - sorry.
Family wrenching - worked with me and my daughter - now a true petrol head. She recently gave me back one of my 7 series BMW's and informed me that the kick down was sluggish. She only went on a 2.5 mile round trip to the shops. I blame her mother.
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Replace a quart of motor oil with a quart of "Rislone". The stuff helps clean out sludge and dirt.
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Plus one on the Rislone.

JTS 71 Mach1
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You used to be able to buy a product called Engine Flush and you would dump that in the crank case and run the engine for about 10-15 minutes then shut it down and drain the oil. I only tried it once but it seemed to work good. I don't know if it's still available.
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Rislone will do a good job of GRADUALLY cleaning the engine/oiling system between oil changes, which I recommend be done every 1500 miles. Motor flush works well but might loosen deposits too quickly which may plug passages or clog the oil pump screen, and quickly contaminate the filter. It took a long time to build up that sludge. Trying to evacuate it all too quickly may cause more headaches than you think. I would remove and clean out the valve covers and oil passages in the heads. Use a shop vac when you clean out the oil returns in the cyl. heads to prevent any chunks making their way into the engine. Most of your sludge will be located in these areas as it is the coolest area in the engine, and it is also where most condensation will form.
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(07-02-2015, 05:45 AM)gxr02190 Wrote: Rislone will do a good job of GRADUALLY cleaning the engine/oiling system between oil changes, which I recommend be done every 1500 miles. Motor flush works well but might loosen deposits too quickly which may plug passages or clog the oil pump screen, and quickly contaminate the filter. It took a long time to build up that sludge. Trying to evacuate it all too quickly may cause more headaches than you think. I would remove and clean out the valve covers and oil passages in the heads. Use a shop vac when you clean out the oil returns in the cyl. heads to prevent any chunks making their way into the engine. Most of your sludge will be located in these areas as it is the coolest area in the engine, and it is also where most condensation will form.
Great points GXR!
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Thanks! That sounds like my route. Once I get to new spark plugs my plan is to now remove the valve covers, cleans those out, and then start using Rislone.