If I were you I would be more concerned. You could send the sample from your water tank to an oil lab to be analyzed, or use a combustion gas dye, to find out if the oil in your water is coming from the transmission or the engine. I agree with JimJ, it is probably trans oil and if so it will eventually cause expensive damage to your transmission.

 

+1 But this vehicle is likey equipped with an engine oil cooler in the radiator as well. If the mixture looks like a chocolate milkshake it's likely enigne oil and if it looks like a strawberry milkshake it's likely transmission fluid. That's assuming the trans fluid is not dark and discolored from being overheated and burned.

 

Don't believe there is an "engine oil cooler" in the rediator.

 

My 97 Tahoe with the 5.7 had the trans cooler on the passenger side end cap of the radiator and the engine oil cooler on the drivers side endcap of the radiator.

 

Most GM trucks have them, not all but most of them. And yes, the trans cooler is on the passenger side and engine oil cooler is on the driver side of the radiator.

 

Spicoli, good point, I hadn't thought about the engine oil cooler.

You can always find out, at least in general, the condition of the ATF just by pulling the dip stick. If it still looks bright red then I guess it would be if it's getting into the water, too; but if it's really old, and in the case of this truck, it probably is, the ATF may not be easily distinguished from the engine oil.

That's why I mentioned a combustion gas test, or an oil analysis of the water sample, as these should both tell him something more definitive. But with the ATF level low... he will either do more diagnostics or keep driving it until something breaks, and find out the expensive way!

 

so i found out what it was....apparently the leftover in the bottle did the same thing...turns out the gas station i got it from, their distributor give him recycled antifreeze so i flushed it out