I accidentally added 1 quart of Motor Oil into my transmission fluid what would happen?
My car has 113000 miles.
My car has an automatic transmission.
If after you did this, you did NOT run the engine (thus operating the torque converter and oil pump in the transmission), nothing untoward will happen. The solution is to immediately remove the transmission oil pan, let everything thoroughly drain out, replace the filter, re-install the pan and refill with new (preferably synthetic) transmission fluid. Run the car for a day and then repeat that operation just to be sure that no traces of engine oil remain. If you already operated the engine, engine oil has been entrained throughout the transmission and you will have to go through multiple drain and refill cycles to reduce the percent oil contaminant level to a de minimus amount. But, such decontamination is doable and if you are diligent you can get the oil out and you will be none the worse. Putting engine oil in the transmission is not as bad as putting "oil" in a hydraulic brake system. If that happens, much of the brake system has to be rebuilt. If you request, a certified mechanic from YourMechanic can perform these transmission fluid exchanges at your location.
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