If you accidentally pour a quart of transmission fluid instead of engine oil?

Transmission Fluid acts like a 'detergent oil'... only more so! it will most likely decarbonize your engine. Sometimes this is a good thing depending on how many miles are on the engine, however, if the engine has high milage the fluid is likely to disolve the carbon build up in the piston -ring grooves, this may cause the engine to start passing oil past the rings into the combustion chamber (burn oil). In any case, it is a lubricant and will not harm the engine's components.... Since the viscosity of the fluid may not be within the manufactures specs for engine application,....best change the oil to be on the safe side.