hello;
I just had my 99-S10 Blazer 4.3 engine fully rebuilt.first i want to say that it only had 80.000 miles on it when it spun 4 bearings inside.This engine never took any extra fluids between oil changes. the day the engine dumped,it was running smooth,then within 1 mile,it died. while i was waiting for the wrecker, i checked the water,only lukewarm and full to the full mark.then checked the trans fluid-normal.checked the motor oil-was blazin hot steaming from dipstick tube-burnt my fingers from touching the dipstick-on full mark also-but very hot.I was using AMSOIL synthetic oil.used for 4 months.Had 2000 mile on this oil change.the oil was on the clean side-not grey or black( motor shop said water was the cause of motor blown) If water was the cause wouldnt the oil look greyish black?.I made the mistake of not getting a sample of the oil before it was torn apart.to get it anilized. I truly beleave it was the Amsoil that caused the motor failure.I had the same thing happen 10 years ago, they gave my mech a lame excuse to get out of paying for damages. talked to another mech ,told him the situation.he told me, the oil lost its velscocity.now if that happened.would it spin the bearings and simulating the effect of water in the motor? He also told me i wasnt the only one to get stung with amsoil oil.he had dealings with this company before.he also said that of the motors that he rebuilt,using Amsoil.the company had an excuse for every motor to get out from paying for damages.DO NOT USE AMSOIL.Bad product.I didnt learn my lesson the first time.
Im not going to use synthetic again .
been talking to alot of people aand trying to figure what would be a good oil to use in a new motor.some suggestions were;Shell rotella,Castrol gtx,
Im up for ideas. Sorry for the long post, but i had to tell somebody.

I have been using Mobil 1 for the last few years but if you want a good regular non synthetic oil I would recommend Castrol GTX.

Although I would recommend Mobil 1 without reservation, I would say the same thing about AMSOIL products. Don't use Rotella - for diesels

I have a hard time understanding how your oil could get so hot with only 1 mile of driving. I have never seen or heard of such a thing.

Water (or antifreeze) in the oil makes the oil look like milky crap, not clear at all. Maybe your oil pump died or you lost pressure some other way. It still doesn't answer the question about why your oil was so hot.

Another possibility was that your thermostat locked shut and your engine overheated. But within 1 mile? Normally thermostats stay closed that long anyway. Possibly you drove alot further than that without realizing it and you had a cooling circulation problem.

Rotella is an all fleet oil, and bought in the correct viscosity range, a far, far superior oil for being organic based. It's full synthetic version is just plain awesome, but hard to find in less than a 15w-40. (Would only use Rotella-T organic in warm/summer climates) I used it for over 10K miles in my 4.3 with no ill effect as a clean up oil during the past summer - then German Castrol 0w-30 went in. Runs like butter, and squeaky clean/spotless inside the engine. ;) Castrol GTX is an excellent oil whether you're breaking in a rebuilt, or keeping an old road roller going. Mobil-1, though it is an excellent oil tends to make the GM 4.3 run a little louder and produces on average more wear metals than even a dino oil. If you want Mobil-1, run 10w-30 in the crankcase. I personally would never touch Amsoil because to me it's not that much better than what can be found commonly on the shelf and their sales-folk types just make me suspicious. I have yet to have an intelligent conversation with an Amsoil Rep. that really knew thier product, or how it stacks against others. Though it is fun to hear them make outrageous claims at the drop of a hat - and tout how it survives a wear test that has no bearing whatsoever on real world driving situations.

So what to do? I would say run the newly rebuilt engine on Castrol GTX for about 1000 miles. Drain and refill again with more GTX 10w/5w-30 and run again for 3k with a new oil filter. Drain and refill with synthetic of choice and go 5k miles on that before changing oil and filter. Keep doing it every 7k miles and you shouldn't see too much trouble ever again.

My choice in synthetics in order of preference: (Open to discussion)

German Made Castrol Synthec 0w-30 [this is an all-season fill] (If available where you are-makes these engine run like no tomorrow. I let a single change of this run for 12k/1year with 6-7K oil filter changes in that time)
Shell Delo-400 Synthetic (a tad on the expensive side, but nearly bulletproof in the 4.3 engine for over 12k Miles/1 year too. Again, keep changing filters on schedule)
Mobil-1 10w-30 [all season fill](Not 5w-30)
Mobil-1 Truck & SUV [all season fill](It's a reformulated Delvac Synthetic 14w-40 at a fraction of the price and again, extremely durable and potent oil)
Shell Rotella-T 15w-40 Full Synthetic [all season fill] (Flows great on cold starts and in winter)
Shell Rotella-T 10w/15w-30 Organic [good in mild winters where it does not drop below 25 degrees] (Rare oil to find, but can be found by the jug at Walmart)

Organics:
Havoline 5w/10w-30 (All Season fill)
Castrol GTX 10w-30 (All season fill)
Trop Artic Semi Synthetic [all season fill] (Can find it only in 5w-30 in my area)
Valvoline High Mileage 5w-30 (All season fill)
Mobil Drive Clean 7000 5w-30 (all season fill)

The GM 4.3 smallblock 6 thrives on thicker oils, especially in low-reving, high torque situations like when rock-crawling. My fill of Castrol 0w-30's much more like a lightweight 40-weight oil, but the truck cranks over quick as lightning in the cold months with no startup noise and with *no* appreciable wear. Though the oil can very handily outlast the year, I still swap filters on schedule according to my truck's manual and top-off any oil lost when the filter's swapped. The 5w-30 weight of Mobil-1 synthetic/Extended Performance is actually much thinner than advertised on the bottle and tends to just be burned by these engines. Not at all worth the money, but a 10w-30 or thicker formulation as labeled on the bottle works very well. Keeping it in the crankcase for at least 7k miles or as long as you can let yourself go and sleep well at night is possible, and recommended. These more expensive sythetics are money tossed down the drain if you do not at least let them run for as long as your book says to. Extended oil drains should only be done after a sample is captured at what you feel is the last leg of you oil's life and sent in for analysis. Each engine is different, even the same model in the same application has variances. Mine goes a solid year on the good stuff, again, filter being changed every 6months/6-7K miles and topped off with fresh oil of the same type. There you go, my take/philosophy on oils and whatnot.

Hot oil and cool water is characteristic of a huge air pocket or restriction or low on coolant. I agree with your motor shop.

My recommendation is to use Amsoil again , then you will know for sure. Break engine in on regular first.

Here's another related discussion on BITOG:

http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=013642#000011

The oil being so hot on the initial failure is cause by the additional friction of the failed bearings, the question is what would cause the bearings to fail on a well maintained engine.

hello;
I just had my 99-S10 Blazer 4.3 engine fully rebuilt.
been talking to alot of people aand trying to figure what would be a good oil to use in a new motor.

The most important person to listen to is the guy who rebuilt the engine. If he is giving warranty, use whatever he tells you to use.

The oil being so hot on the initial failure is cause by the additional friction of the failed bearings, the question is what would cause the bearings to fail on a well maintained engine.

You may be right, however, this is a chicken:egg thing. It is very likely that the hot oil could have caused the bearing failure. The hot oil could be caused by lack of coolant flow (only if driven more than a mile... I think). Since the bearings do not sit in contact with the bulk oil in the pan, it is hard for me to envision how they could have heated up the oil so quickly.

I will be the first to admit that I haven't been in contact with many seized engines immediately after they fail to know what is normal in this case. When my engines have failed, usually there is a huge puddle of oil following me down the street and I don't have to think too hard about what happened.. :)

BTW, here are a couple of interesting perspectives on how to break-in a new engine:

http://www.mototuneusa.com/break_in_secrets.htm

http://www.lycoming.textron.com/main.jsp?bodyPage=/support/publications/keyReprints/operation/engineBreakIn.html

Okey;
i want to clear up some things on my first post.I stated the that the engine died in within a mile. what i meant,i was hunting with friends from9am to4pm(coyote) stopping,parking.then moving on to another section or square mile to hunt.it died on the way home,20 miles away.got withing 10 mile from home,running 60MPH.started to spit,sputter,loose all power then died(within 1 mile)before that it ran smooth and normal. checked all gauges when it started to act up.all gauges read normal,no engine light came on iether.water didnot get hot,took off rad cap and water was just above lukewarm(could put finger in water).the oil was at normal color for 2000 mile on this oil change.but blazin HOT(like boiling).it has Penzoil in it now,thats what the mech put in it. A bunch of people told me that Pensoil was not good oil to use.Was told to change oil at 1000 miles.not decided what to use yet after the 1000 mile are up tho.seems that a lot are using mobile one.should i still use regular untill maybe 3000 miles or should i use the mobile 1 after 1000 miles???? i spent 2600.00 plus on the complete overhaul. Has anyone had any problems with Mobile1 oil.This considered a New motor now.Should i put in the Mobile1 after the 1000 mile or wait till i get 3000 mile on before using Mobile1??HMM i think i just repeated my self.LOL. I live in west-central Ohio.It does get pretty cold in the winter here.what grade should i use? You guys are great and very helpfull .Somebody said something about the oil pump. where is that located? in the engine somewhere?:banghead: :banghead: :banghead:

I assume there is a warranty on the engine? Use whatever recommendations the rebuilder suggests to cover your ass. I would use a high quality dino 5/30 for a couple of thousand miles and go to synthetic if you prefer. At the first oil change I would have the oil analyzed and/or cut open the oil filter and see what is trapped in there, this is an indication of general engine condition.

http://www.lucasoil.com/ use ther oil great stuff 4qt of ther full Lucas Synthetic High Performance Motor Oil and 1 of ther
Lucas Synthetic Oil Stabilizer repost wat you went with

I would suggest using Castrol 5W30 for at least a few thousand. Definately change the oil at like 100, 1000 then 3000. I wouldnt let a brand new engine go 1000 miles without changing the oil.

Go to Mobil 1 either 5W or 10W30 after the bearings have seated. I know many people including myself that run Mobil 1 only and get tons of miles with no engine problems. My last vehicle, 1996 Sierra 5.7 liter had 189,000miles on it when I sold it. I could pull two Sea-Doos and hardly know they were there. The engine ran smooth as can be right up until I sold it.

Also you must allow the bearings to seat before switching to synthetic. Otherwise your break in will take 3 times longer. It happened to my brother with a 3.1 liter v6. Took over 10k for the bearings to seat properly.

Hello;UPDATE
I think what im gonna do is change the oil on sunday with castrol 5w30gtx it seems to be a good choice of alot of users. I have around 500 miles on the new engine at this time.it has pensoil in it now.(mechanics choice) or should i stay with pensoil then put on ,say 1500 mile on that oil. then maybe go to Mobile1.or should i put more mile on before going to mobile1???????????More imput please!!!!!!!!!!!!!!!!!!.I just want to do this right, never had a vehickle with a new motor:banghead: :banghead:

I am getting mine back from rebuild monday. I am going to go 500 with whatever they put in it. Then 1500 with Castrol GTX 5W30 and then to Mobile 1 10W30 and have it analyzed at 5000 miles and see whats in it. Then if all is good back to 7500 miles on each oil change.

BTW - If you ever want an oil analysis done, this is the place, they will send you the test kit free and its just 20.00 for a standard analysis.

http://www.blackstone-labs.com/