2002 Chevy Venture Low Coolant and Oil?

[86CapriRS]

Hello Everyone,
I'm new to this site and I'm hoping someone can help me out. I have a 2002 Chevy Venture with a 3.4L V6 that has 150,000 miles on it. It has served my family well, having been in for repairs just once.
It's taken me this long, but ever since it hit 100,000 miles, it has been slowly "eating up" coolant and engine oil. Every few days, I'd have to put in more coolant in the radiator and put in engine oil every few days also.
I've checked and there are no leaks and it isn't blowing thick white smoke out of the exhaust, so I'm a little confused as to why the coolant and engine oil level keep dropping every few days.
The van does have a rear heater core system, but again, there are no signs of any leaking.
I'd appreciate any help anybody can give me to solve this problem.

Thanks so much in advance.

[Tech II]

You have lasted 50K miles with a coolant leak and no problems have occurred, like overheating, misfires, lack of heat from the registers?

You have lived a charmed life, my friend....

If there is no EXTERNAL leak, then it has to be burning up in the engine. Sometimes a leak is so small, coolant dye needs to be used...

Vehicle is famous for lower intake leaks, w/p leaks, hoses, radiators, head gaskets(which usually happens when a problem is not fixed, coolant is just added).....

It boggles my mind that you have lasted 50K miles since this first started....

You have to have leaks(oil and coolant), if you are adding as often as you say you have....

[86CapriRS]

No, I can tell you that the temp rises in stop-and-go traffic, but the heater works just fine.
I've been searching for leaks and have found nothing. I let the van sit and warm up and there's no thick white smoke, which indicates a bad head gasket, coming out of the tailpipe.
Believe me, it boggles my mind too.
I will start with the coolant dye first, though, thanks.

[Cressidaadr]

I agree with Tech II.

I'd take an oil sample and send it in for analysis. Then you will know more about what you are dealing with.

[rhandwor]

Originally Posted by 86CapriRS

No, I can tell you that the temp rises in stop-and-go traffic, but the heater works just fine.
I've been searching for leaks and have found nothing. I let the van sit and warm up and there's no thick white smoke, which indicates a bad head gasket, coming out of the tailpipe.
Believe me, it boggles my mind too.
I will start with the coolant dye first, though, thanks.

Napa sells a test kit to check for burned fuel in the anti freeze.