I realize that this is a pretty generalized question that could have several answers but I want to get an idea of what I'm more than likely dealing with... The 5.3 has 88K on it and has never been apart. It has run strong every since I bought it with 22k on it, and still does to this day. It has always been serviced on time Mobil; the oil is always brown and pretty clean when I change it.

I have noticed that it's been using a little oil over the few months. The truck doesn't smoke that I have ever been able to tell; the exhaust is dumped so it's a little harder to see, but I'm sure I would have realized it by now if it was. I don't get to park it on concrete very often, but when I do there's never any oil puddles that I've noticed. It seems to have burned a little more than normal when checking it after pulling my bass boat around 300 miles at 70mph last weekend. What are the most common reasons for these engines using oil? No leaks and no smoke has me somewhat stumped.

Also, it has been using coolant for awhile now. I can't really tell if it's coming from the water pump or not, but I have never noticed any coolant puddles under the truck which makes me think that's not the problem. Could the coolant evaporate from the engine heat making it less noticeable? There is no sign of coolant in the oil. A cracked head or bad head gasket comes to mind, but I'm not sure. Could it be burning coolant, making it undetectable?

 

the oil could be from a pcv problem. check the pcv valve on the drivers side head back by the firewall. it will have a little check valve that will sometimes stick open. the pcv valves are only a couple of bucks to replace. if it was burning coolant, you would most likely see a small amount of smoke, also it would have a sweet smell to it. how much oil and coolant does it use?

 

GM had a problem with certain Castech heads where the motors would start to use coolant. GM putout a bulletin i searched and found this...
This is a couple bits and pieces of the bulletin.
http://www.gmfullsize.com/forum/show....php?p=3308817

 

I just replaced the PCV valve around 6K ago... IIRC the one I replaced was stuck closed... I would say it wold fall probably two hole's from the full mark over 2K miles. Maybe a little more, maybe a little less, it's hard to really put a mileage to it and I haven't paid attention to the date's well enough to remember. As far as coolant, my light will come on every 5-6 weeks I would say. Probably a quart over that period.

Thanks for the help. I will try and look for the Castech emblem online and then check that. sounds promising lol