I really hope one of you can help me out here, or maybe you're familiar with this problem:
I'm having a lot of mysterious issues with oil in my 1989 Cadillac Brougham. It doesn't smoke, and doesn't leak, but there's many times when i check the stick, there is little, or no oil on it. Sometimes it's in different spots on the stick, in patches, or only on one side.
It seemed, that after I bought it, to get anything on the dipstick, I had to add oil often, and once or twice the engine got noisy and i added more immediatley. In the fall i had the oil changed, and there was there was plenty of old oil that came out. then after a month of driving or so, I took it off the road and it's been in the garage since. I turned it on for the 3rd time this season today, and it was making a loud tapping or clacking noise. after I shut it off, waited and checked the stick, it was a little patchy, so I added some more. i got a little more to appear on the stick, and i turned it on again. the noise was still present, but it went away after awhile. it ran perfectly smooth, as it usually does, for the remainder, with out smoking or leaking.
it's very odd. i really don't know what's going on. does anyone else have any problem reading these dipsticks? it seems like it's inconsistant and tough to read. sometimes it says nothing, and then without adding any, all ofthe sudden, it reads like it has plenty in there.
yes, i wait for the oil to return to the sump, and yes i put the dipstick in all the way. really puzzled here. anyone with similar issues?
I dunno, please tell me what you can, those of you who are used to this motor, or have had something like this go on.
Funny, my 87 w/307 did the exact same thing. I remember seeing patches of oil on the dipstick and adding oil quite a bit. I too had no leaks and visibly saw no smoke. It was puzzling but it kept running great. I sold it but the answer to your question is yes, I know exactly what you are talking about.
Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
Re: Oil Disappearing Act in the 307
Another reason could be the oil return holes in the cyl heads are plugged with crud. Overnight the oil would finally reach the pan and give an accurate reading. These engines would cook the oil in the valve train on the side the EGR valve is located. Remove the valve cover on the EGR side and inspect for lack of oil or plugged drains around the push rods and the rear of the cyl head. The crud , if present, should be sucked out not poked thru to reach the pan. You can plug up the oil pump screen possibly!
Mine never did start to do it, even at 186K miles when I broke it and had to pull it out.
BUT, knowing Olds V8's, as carnut also said, the oil drain back holes in the heads aren't that big and can easily get clogged with crude. as the old saying when you opened up an engine seeing oil coked up everywhere "Look, a Quaker State Engine", as it often the older Quaker State oils were known to be pretty crappy. Years ago people always said to get a Pennsylvaina crude for your car vs a Texas crude. I can't say I could tell a difference, this came from older mechanics who delt more with the crappier oils in the shop. I have seen a Ford 351M that when the we took off the intake (all 90 lbs of it!) the oil was at least 1 in thick in the lifter valley, all solid coked up. NASTY.
Synthetic might be a help to see if it is getting past the rings. Go to a 10W30 or 15W50 Mobil 1, ot a 10W30 or 20W50 Amsoil oil, for one or 2 oil changes and see if the oil use stops. Synthetics are known for helping seal the rings better and stop some of that oil loss. The film strength of synthetics is supposed to be stronger and help this. Is it? Don't know for sure. It is claimed that way...
Also, engines that don't get a lot of use "appear" to have a oil loss, which is some of the moisture that is in the oil that isn't getting boiled out as the oil gets up to running temp for long enough (why GM spec's more frequent oil changes to engines that get driven in short trips often).
Also, Amsoil claims that there is oil loss due to the vaporization of the oil. http://www.amsoil.com/performancetests/g1971/index.aspx. Typically Amsoil oils are rated well on this. Is it important? Well, yes I can see it might be, especically in harder driving conditions, as the oil that is vaporizing is getting vented into the PCV system and that oil there, increases the octane needs of the engine unless it is captured somehow so it doesn't get ingested into the PCV valve or sucked in through the PCV vent in the intake (see how much oil is in the separator on the valve cover??)
Just be aware that synthetics can "clean" the crud off the seals and gaskets and cause more leaks than before, so use synthetic on an old engine with caution. In almost every engine I have had, if I used synthetic when the engine was old, at least 1 new leak did appear.
Typically something like front cover (Ford 4.0L V6 that I put synthetic in at 200K+, the engine was still running at 280K....) or a oil pan or rear main seal or valve cover..
Synthetics are good and bad. They don't ADD detergent to them, but they have a detergent action as part of the base stock chemical design (Ester and DiEster base stocks). Almost like it is a solvent.
Just use with caution. A good high quality 15W40 like Rotella T, Delo 400 or Delvac 1300 is my preffered choice in most any high mileage engine. I have done extensive fuel economy testing over the summer and winter months and seen nearly zero economy change with 5W40 synthetic (Rotella T) vs 15W40 Delvac 1300 and Rotella T. The average driver will NOT see anything significant in fuel economy by running thinner or thicker oils.