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Discussion Starter · #1 ·
My truck just hit the first oil change mark(according to the consel)in the research i have found i have got no answers. is it okay to add synthetic now or will this harm the break in period? I am at 4000 miles in a 2008 3500 6speed and new to diesels, does any one have any advise.I also do a lot of in town stop and go if that changes anything.
 

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I read once on the cummin`s site that you should waite till 20,000 miles, I did with mine and works just fine.
 

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The big question is have you worked the engine at all during its first 4,000 miles to help seat the rings? If not then wait until you do work the engine for 4-5K and then change over to synthetic oil. One other though if you plan on using a synthetic oil like Rotella, Mobil Delvac, Valvoline then it may be Ok to use it right now (these oils are only highly refined group III dino oil that can be called synthetic) but if your going to use 100% group IV or V (man made) synthetic oil like Redline or Amsoil then wait until you have at least another 6,000 miles on the engine.

jmho
 

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Rings get seated on the first heat cycle...
 

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I put synthetic in at 6000 kms. No problems since. I replaced the factory oil with synthetic for cold weather advantages.
 

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I changed to Amsoil synthetic at 7,500. She hasn't used a drop in 4k. I'm happy with the results.
 

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My motor (CTD 2006) took about 15k miles to break in. I kept getting better fuel mileage until 15k anyway. I would follow cummins recommendations to the T. You want that motor fully broken in before adding synthetic.
 

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Amsoil reccommends waiting one full oil change interval, which on the 6.7 is 7.5K, IIRC.

Personally I like to wait at least 10K on my rigs before the swap. There are several reasons for this. One I can do several oil changes in the first 10K and not be wasting good oil and $$, 2nd is the engines do take time to break in. Mine has 17K and is still creaping up in mileage... My dads crept up until 20K, and he towed hard with it from 500 miles on...

If it were me I would do an oil change at 500, 1500, 3K, 5K, 7.5K, and syn at 10K... I bought mine used and was happy to find the PO had done 500, 3K, 6K, 9K, 10K (by the dealership) and I went full syn at 13K.
 

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i waited till 30,000 miles according to the diesel mistro at the dealership..benn using valvoline 5w40 syn ever since. used to get ok mileage till they changed the fuel -no sulpher-mileage since then never been great. especially towing my 9500lb trailer. fuel today was $1:36/litre. $80.00 to top off 3/8's of the tank. I went thru the senventies when there was rationing and everyone was freaking but this seems alot more af a mess than those days.
Last person to leave the planet please turn off the lights!
 
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