Losing oil AND coolant but no smoke?

Ok this is starting to worry me! On the way home today my car popped a check oil light. Its only been like 1500-2000 miles since my last change. During my last change my leaky oil pressure sending unit was replaced also. I have yet to make sure the new one isn't leaking but i will soon. Also i can top off my coolant and it'll be down to like half radiator in a few days. I cant find any leaks, i dont know if it only leaks when i'm driving down the highway or what but i have not found a coolant leak or an oil leak yet (i look under it after its been parked and started it and looked around). My passenger side carpet isn't wet, car doesn't smell like syrup. So does this sound like its probably a head gasket? When i ran my compression test cylinders 6 an 7 were lower than the rest, but very close to each other. I thought maybe it was because by that time the motor had cooled and messed the test up but maybe the gasket is torn? I dont smell any burning and it doesn't smoke at all. Anyone know what might be going on? I'm going to try to have my coolant system pressurized soon to see if i can find the coolant leak. I have NO idea about the oil leak. I know these cars go through oil when they start putting miles on, but man...its only been 1500-2000 miles. I was talking to my mechanic today and he said its probably just engine wear (dealing with the oil). He said he would disassemble my motor for 150 and a place in the lower part of the state would bore it to 306 and clean it etc for like 80-100 and he would reassemble it for 150 (i would get a rebuild kit to be put in). This seems like a great deal but i really hope its just the gasket or something. Anyways any help appreciated. Thanks,
-GM

Michael Yount said:

How much oil did you have to add after 1500 miles? What were your cranking compression numbers? You're on the right path - have the cooling system pressurized and see what it does. How's the car running? Fuel mileage? Any other symptoms? Overheating? Tell us more...

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After letting the car set overnight i went out this morning and checked the oil. So it was all drained to the bottom by the time i checked it. The oil level is right at the add mark. There is add(boxofmeshedlines)full and its right at the add line. So is that normal consumption? My compression numbers, i dont remember EXACTLY but i remember they were all in the 140-150 area except for 6 and 7. Those were closer to 130 i think. But it took me so long to do the test (like an hour) that the motor was cold (i have equal lengths so it took me forever...stupid headers) and i thought maybe that was the problem. But i think cylindre 8 registered back around 140. These are all after 7 turns. The car runs GREAT except for a high idle which is due to my throttle body. If i lower it the TB will stick so it'll be replaced soon. It does run warm. It always goes up to 2 or 3 marks from the top and stays there a couple minutes then will gradually go back down to about half or a little lower (stock guage). It always runs warm in rain though, ALWAYS. Fuel mileage i'm not sure of as my speedo gear is wrong, but through estimation i believe its around 17mpg give or take a few depending on how i drive it. I dont smell coolant at all. I opened the hood the other day and heard hissing that sounded from the area of the water pump but i could not tell. I hope this is enough info. Thanks a lot!
-GM
p.s. This is gonna really make me sound like an idiot and probably i'll get flamed, but i've been using 100% water as coolant. Is that my problem? Is it just evaporating or something because it isn't mixed? I didn't know anything was wrong with it butu now i know better because i read a thread talking about the antifreeze adding rust protection etc. Maybe thats what is causing the loss?

Ok so apparently the oil thing is fine for a high mileage car like mine (1 qt for 1500-2000 miles). I'll definitely start using a 50/50 mix. I guess i'll need to flush the system and then put 50/50 back in. I'll also check out the cap etc. Thanks a ton guys, at least i've got a lead on it!
-GM