Pennzoil HM 10w30- ~500mi 1988 Chevy Truck 350ci

Status
Not open for further replies.
One person mentioned checking the intake manifold for an internal oil leak. I'd second this, since I know of one person who solved a mystery high oil consumption with that.

My old 305 TBI I pulled from my 89 Caprice has 335k miles on it and it was going through a qt in about 600 miles, but was leaking a lot too. I am going to check the intake manifold on it, since it wasn't showing much of anything on the plugs and compression check was decent. (a couple cylinders read about 20psi high though). I saved the engine to do a teardown.
 
Originally Posted By: edhackett
This one doesn't have stuck rings. It doesn't have rings.

Turn off the oven, Martha. This baby's done.

Ed


You could be right...
 
Wow, thanks to everyone for the responses and suggestions. I didn't mean to leave this post high and dry, but I work and go to school full time, so I don't have much time to spare. However I have a partial day off today! I will try to reply to all who have suggested things.

--I've tried 3 different pcv valves, with no change. It currently has a brand new purolator specified for this model vehicle. Valve covers have been pulled and cleaned when the valve stem seals were done. There was considerable charcoal like deposits, but no vents were clogged. I installed positive type seals on the intake and exhaust valves thinking it would help with any consumption in that area. All pcv baffles are installed, and oil drainback is verified. That area was cleaned as well while valve covers were off. Spark plugs were all pulled just last week and were all normal and not oily in the least except for a the #1 and #2 cylinders. They were mildy oily while still having a light tan/gray color. Oiliness was barely significant on #3 and #4 spark plugs. 5, 6, 7, and 8 were completely dry and looked very clean.

-- I have tried 20w50 high mileage oil with no noticeable improvement in oil use. I returned to 30wt because I believe most of the parts in the engine are still in decent shape and 50wt is not optimal for them.

--Internally leaking intake manifold is a possibility. I haven't given that one much thought, though I will moving forward. I do remember spraying carb cleaner around it and finding no external leaks. I will investigate this further. I heard you could take the oil cap off while it is is running and check for idle speed changes. Not sure if this is the correct way to diagnose it, but I will give it a shot.
--The wear in this analysis was alarming to me, which was why I put 40 wt in this time. I was hoping to help with the bearing wear and the large amount of wear metals floating around. I already knew it wouldn't help with consumption.

--I've tried Restore, no change. I've also tried STP, Seafoam, Kreen, Bars Leaks Engine Oil Stop Leak(seal conditioner), and have been using MMO for about 5000 miles now @ 20%.

-- I will look into the Schaeffers, though I don't expect it will solve the consumption issue. I've also tried Maxlife, (and Castrol, Mobil, etc)but I prefer Pennzoil, especially after seeing the high amounts of additives it has.

-- @edhackett- I've considered that actually. Oil control rings at least. I'm beginning to wonder!!

-- Ring soak is a great idea that I have not tried yet. I will definitely do this soon. I don't have any kreen left unfortuately. What's the next best thing? MMO? Mopar CC Cleaner? B-12?

--SAE 60 = No. I need this vehicle to start reliably, every single time. With our wonderful Arkansas weather, one can never predict the frequent temp swings. I'm also not interested in masking the problem. I want to fix it correctly.

--No junkyard specials for me. I'm at a point where I know, or am very close to knowing everything that's wrong with this one, and I have corrected most of it. I don't want to start over. I have yet to find evidence of anything being worn out besides the valve seals, so until I do, a new engine is not an option.

-- If everything goes right, I will do a dry and wet compression check today and will post back the results.

So as it stands, the list of possibilities include worn or broken rings, cracked block, internally leaking intake manifold or head gasket. I am not sure how to diagnose either gasket and I don't have a leak down tester for to play around with. Yet.. I'm hoping the compression check tells me something useful.

Thanks again to everyone.
 
Last edited:
You have stated that there were 'considerable charcoal like deposits' in the head area when the vc's came off. for only 500 miles, silicon and insoluable are very, very high, and you have been using cleaners.

I'm wondering if you've just loosened/flushed 'junk and deposits' into the oil, and they have stuck the rings and caused wear. I'd grab a lot of MMO, and really, really cheap oil, and do a LOT of 1k miles changes with 20% MMO like you are doing now.

That will hopefully clean out all the grit and junk in the engine. Also, check your air filter and ducting very carefully - it may have been leaking for a while, and grit may have built up in the engine.
 
Sorry, I'm a bit late. It's been a long day. Compression test results are as follows: (looking at engine)

Left side ----- Right side
cyl#8= 160 -- cyl#7= 142
cyl#6= 156 -- cyl#5= 148
cyl#4= 158 -- cyl#3= 134
cyl#2= 148 -- cyl#1= 136


When I did the test, the engine was at operating temp. I started on the driver's side. By the time I got to the other side, the engine had cooled a bit, so I wonder if that affected the readings. The spec is 150psi for this engine. I will do another test of those 4 cylinders on Saturday to make certain of the readings. I tried doing a wet test on a couple of the low cylinders, but it kept shooting up to like 250psi and that didn't seem right, so I just did dry testing only. Also, cylinder 1 and 3 spark plugs were oily, and cylinder 1 and 6 spark plugs had electrodes covered in white ashy buildup.

I'm still just as confused after seeing these results. How low is too low?? I don't think 134psi would cause 150 miles per quart unchangeable oil usage. Or could it? It is very consistent, no matter what weight oil/additive is in the sump, which makes me think rings are not the issue here.

Btw, Eclipse is in a million pieces. It threw and completely chewed up the timing belt. Hoping it didn't bend the valves. I'm working on it, slowly but surely, as it's not smart to keep driving this thing which is wasting my money and polluting the air.
 
Originally Posted By: FL_Rob
Originally Posted By: troyb43
How about some sae 60?


no ..that would make things worse ..
he needs to thin out the oil around the ring lands to introduce fresh oil to the rings.along with solvent.


interesting... if I were at the end of my rope like the OP I guess I would try some 20 weight with MMO.

Other wise I'd load up on ST 15w-40 HDEO and run it until it dies.
 
Originally Posted By: NP_350
Sorry, I'm a bit late. It's been a long day. Compression test results are as follows: (looking at engine)

Left side ----- Right side
cyl#8= 160 -- cyl#7= 142
cyl#6= 156 -- cyl#5= 148
cyl#4= 158 -- cyl#3= 134
cyl#2= 148 -- cyl#1= 136


When I did the test, the engine was at operating temp. I started on the driver's side. By the time I got to the other side, the engine had cooled a bit, so I wonder if that affected the readings. The spec is 150psi for this engine. I will do another test of those 4 cylinders on Saturday to make certain of the readings. I tried doing a wet test on a couple of the low cylinders, but it kept shooting up to like 250psi and that didn't seem right, so I just did dry testing only. Also, cylinder 1 and 3 spark plugs were oily, and cylinder 1 and 6 spark plugs had electrodes covered in white ashy buildup.

I'm still just as confused after seeing these results. How low is too low?? I don't think 134psi would cause 150 miles per quart unchangeable oil usage. Or could it? It is very consistent, no matter what weight oil/additive is in the sump, which makes me think rings are not the issue here.

Btw, Eclipse is in a million pieces. It threw and completely chewed up the timing belt. Hoping it didn't bend the valves. I'm working on it, slowly but surely, as it's not smart to keep driving this thing which is wasting my money and polluting the air.


So 1,3,7 are low. The white ashy build up is burned oil. So that is where your oil is going.

Do you have anything like a boroscope you could use to look into the offending cylinders?
 
I can't help but wonder if using some Kreen in this app as a piston soak would help at all? I'd also try an idle time flush prior to draining one of these short OCIs in an effort to get things 'unstuck' if the rings are going to be functional again in any way without a rebuild. I'd probably even try 16 ounces of Kreen at idle on fresh/cheapest conventional oil you can get for 30 minutes, drain and perform a couple of rinse intervals with some HDEO like T5 along with a pint of Kreen; for an entire OCI, of at least 1,000 miles as addguy mentioned. Adding a blend of Kreen or MMO with oil during top-ups. If going beyond 1,000 miles...change out the oil filter by 1,000. Don't waste your money on a top-end oil filter, but also make sure the 'basic' is still of solid construction.
 
So the suspense was killing me and I did a retest this morning. I tested the opposite side first and got lower numbers, and on the other side that had cooled a bit, I got higher numbers(+about 10psi)than yesterday. This is a brand new, known-accurate gauge that has been used before with repeatable results. I will use the lowest numbers obtained from both days. The final results are as follows.
(standing in front of vehicle, looking at engine)
Left side ----- Right side
cyl#8= 148 -- cyl#7= 142
cyl#6= 155 -- cyl#5= 148
cyl#4= 158 -- cyl#3= 134
cyl#2= 136 -- cyl#1= 136

I am thinking maybe there are carbon buildup problems that are skewing the readings. Carbon or no carbon, there are a few low cylinders: 1, 2, 3, and 7 is borderline. Is this low enough to cause excessive consumption? One can only guess. I am doing a piston soak soon as a last ditch effort before pulling the intake manifold and replacing the gasket. If that doesn't work, the options are drive it till it dies or replace/rebuild the engine, whichever comes first. Thanks for everyone's advice and help!
 
For a piston soak, a really good product is AC Delco combustion chamber cleaner if you can get it. The stuff removes carbon, varnish, anything really.

I'd spray directly into each hole liberally with the plugs out and let it soak for a few hours. Roll the motor over a bit, to spread it out, spray some more in, and let it soak again. Then put the plugs in and fire it up. It will probably look like you are burning down the neighbourhood, but if anything will get the varnish off those stuck rings (if that is in fact the issue) it will be that stuff.
 
Some more thoughts:

I've read that 'good' compression readings are all cylinders within 10% of spec. pressure, so you have that, although 'just' on a couple, so that's pretty good.

It's a bit radical, but a great option to get rid of large amounts of carbon is a 'water decarb'. I'm assuming this engine had a TBI system, so try this...

Get the engine goosd and hot, don't do it on a cold engine.

Open up the air cleaner, and using a spray bottle, liberally spray about 1 quart of water into the throttle body while revving the engine manually.

It will bog and sputter, but by using a spray bottle you shouldn't be able to introduce enough whater to hydro-lock the engine.

Take the vehicle for a good, long drive after to get all the moisture out. this process will steam carbon off both the pistons, and if the steam gets into the ring lands, it will eremove carbon from them as well, and help free-up the rings.

I've done it to a 2002 Cavalier, and the thing ran noticeable better after.
 
I see a lot of these V8 Chevy trucks in the UOA section with high wear numbers while using
thin oil. I can say with a certain degree of certainty that 10W-30 is too thin for your engine.
 
Status
Not open for further replies.
Back
Top