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Hello Everyone, I just bought my first used Duramax, Its a 05, GMC, LLY with 58,000 miles. The old oil had 5,000 miles on it and it was very dirty looking. I went over the fluids and filters, Changed motor oil + filter, Trans oil + filter, Fuel filter, Air filter, and Transfer case oil. After I changed all theses I ran the motor for about 5 min. to check for fuel and oil leaks, everything was fine, I then checked the motor oil and could not believe my eyes, It almost looked as dirty as when I started. Should I change it again in about 500 to 1,000 miles or is there a way to flush the motor. I dont think this is normal ? No service engine light, Everything seems to be normal, Any insight or help would be greatly appreciated, Thanks
 

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Ya its definatly normal. I checked mine after my first oil change at 2500 miles and it was dirty. Diesels get alot of soot in the motor from the EGR and Blowby.

Since you just bought the truck. I would do exactly what you said. Change the oil in about 1,000 miles change the filter in 500. Oil has alot of detergents in it so changing the oil more frequent will help. My dad has been a mechanic for 35 years he always said to me. "Son oil is the cheapest insurance for your motor you can buy" :D



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I use Amsoil 15W-30 exclusively and find that it doesn't start looking dirty until about 7500 miles or so. Maybe try Amsoil? My mileage inproved with the use of it also.
 

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Some trucks will do that. The MACH's are notorious for being black before they get out the shop door. All oil does turn darker in color in time and may not indicate that's it's necessarily dirty. Only way to know is to take a sample and send it in for analysis. With good filtration, it shouldn't be a worry. Since the vehicle was new to you, an engine flush might not be a bad idea, but not always necessary. You don't have many miles.
AMSOIL would offer some advantage as it has good dispersant additives to suspend those soot particles IF they are accumulating quickly on you. Helps to delay varnish and sluge formation.
Good luck,
Heath
 

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If you are going to do another change, I would get a good quality engine flush. I use Amsoil's engine flush when converting motors over to syn. It helps thin the oil slightly and flush more of the junk out, and more of the old oil. That way you are starting fresh with clean internals. Either way, you are going to get alot of soot in the oil. About the only way to stop that is to install a bypass filter, which will remove a large amount of that soot, which is 1-4 microns in size. Most oil filters hit the 25 micron and up stuff.
 

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I am fairly new to the diesel world and read up that we should check our diff. fluids in both, if you have it, my question(s) are what type of differential fluid do i add and also can i mix something like Amsoil synthetic fluids with whatever is in the diiferential now.

Also putting on a new trans filter, i purchased a fram, don't know if there is a better one out there or not, and was wondering if it is ok to just add more fluid into the filter even if it is not the same as that was previously in there.

hope these questions make sense.
 

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Hopefully you're not having to mix diff. fluids because it's low...just replacing old I would assume:) Switching to AMSOIL or synthetics in general is fine.
As for the trans fluid, if you're needing to change the filter, aren't you changing the fluid as well? Mixing with AMSOIL's TorqueDrive is ok, but not recommended. If changing fluid types, draining and replacing with new would be preferred.
FRAM??? Donaldson is another reputable brand or OEM.
Heath
 

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Amsoil is perfectly compatable with both conventional and synthetic lubes. Synthetic would be preferred for your transmission, but for now you will be fine.

For the diffs, again, you are fine to mix them, but better to change the fluid. Its good to change the fluid and clean up the magnets inside the diffs anyways.

I would not trust a fram on my lawnmower. Never. Thats an expensive transmission in an expensive truck, why not spend a few more dollars and give it the quality filter it deserves? I severice Allisons here with the Donalson Part Number P550606
 

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I did two oil changes in one week and still looks dirty.Won't hurt anything,it is left over soot/old oil.
 

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Its just a typical diesel,,, They all do this in my experience....
 

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I do a lot of larger engine repairs and overhauls. I reading up on duramax,s because i'm going to buy a new truck when i sell my house and move up country. But back to the issue of dirty oil a very good flushing agent that i use at home and work is on a 10 litre type fill add 2 litres of ATF and take it for a 10 minute leisurely drive at low RPM and power it will clean up the gelled oil sludge you get inside most engines especially if it is running cooler than it should be. PLAY SAFE!
 

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Ive heard of putting tranny fluid in your oil just before changing your oil. I guess ATF is a very high detergent. I have been thinking about doing that to my truck but i kinda want to wait till someone else does it first
 

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ATF is a very high detergent oil it has very good lubricity. I did a bearing roll in on a 60 series on Friday that had 900 thousand k on it. I only put in 2 litres of ATF the oil capacity of that engine is 38 litres it cleaned out about 90% of the sludge and all the jellied build up you get with any engine that has not been opened up before and had not had regular servicing. PLAY SAFE!
 

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