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Tons of internet research and still at a loss- oil to use

8K views 31 replies 12 participants last post by  elkhornsun 
#1 ·
I recently purchased a 2015 2500hd duramax 6.6 diesel and no one can tell me with complete certainty what type of oil to use. The dealer told me 15w40 fully synthetic. When trying to find a comparable oil to ACDelco for me it's been next to impossible. Will Shell Rotella T6 work and is it comparable with CK-4 and the ACDelco brand? Is CK-4 the new standard or should I go with CJ-4? I've never been so confused about an oil change in my life. Thanks in advance
 
#2 ·
Did you see all the information on Shell's web site? Big page on Q&A. they say yes to Rotella T5 or T6 As a replacement oil for CK-4 which is the updated CJ-4. You can always look or ask on the site (Bobs the oil guy)dot com.
 
#3 ·
Thanks for the heads up. My dealer told me to use 15w40 full synthetic and that's it. I assume the rotella T6 is the correct oil. I'm looking for the best quality full synthetic oil I can find at Walmart or the local Autozone.
 
#4 ·
T6 is full synthetic.
 
#6 ·
CK-4 is the new standard for 01(& yrs before)-16 diesels. Pick a brand DELO MOBIL ROTELLA are all a good pick. Mobil filter is a top pick.
 
#8 · (Edited)
Red Line, Am$oil, Lucas make a 15w-40 synthetic. You don't need a full synthetic 15w-40. Many are using a 5w-40 yr around with no problems.
 
#11 ·
7500 if still stock and 10,000 miles if deleted are solid numbers for interval

~the Captain

2016 Chevy 2500Hd, PPEI tuned, CAT back exhaust, 2.5" Zone Level Kit, Moto Metal 970 wheels/Nitto Terra Grapler G2's, Custom Cab lights, LED Fogs, Resonator deleted
 
#12 ·
My truck is older so it never had any emissions junk on it. Been running Mobil 1 5W-40 in it almost since new. I say almost because they did not make Mobil 1 for turbo diesels when I bought the truck. Had to wait about a year before it came out. Ran Mobil 1 in my last 2 gas trucks 250k and 275k miles on them with same change interval. Both were running fine when I replaced them - no smoke ever.

Anyway, I change every 10k miles.

Currently 366k miles.
 
#13 ·
Thanks for the info. All the dealerships around here in the Houston area say only use fully synthetic 15w40 in a 2015 6.6 Duramax. I'm curious though why 5w40 is frowned upon. It appears that most readily available fully synthetic diesel oils are 5w40 (i.e. Rotella T6 Valvoline Premium Blue, ect). Would I run into any issues using 5w40 in this extreme heat here in southeast Texas? The dealerships tell me the ACDelco 15w40 they use at the dealership for oil changes is a fully synthetic oil. Even though the 5w40 meets the CJ-4 requirement they still only use 15w40 down here.
 
#16 ·
Thanks so much for the info. This is what's so confusing... I'm being told by the dealers the ACDelco oil they put in the 2015 6.6L diesels is 15w40 full synthetic. Is this true?

If this is true there aren't many after market oils that are 15w40 full synthetic. I'm really suspect of what there saying because it's all about the API CJ-4 requirement and to my knowledge there are conventional oils with that rating.
 
#18 ·
From the factory & or dealers (unless you tell them) is conventional 15w-40 oil. GM has a Mobil/Exxon contract. (The AC Delco labeled fluid is Mobil). Yes it's ok to switch between.
5w-40 & 15w-40 are rated CK-4/CJ-4.
 
#19 ·
My dealer said all new vehicles call for synthetic at dealer unless otherwise requested

~the Captain

2016 Chevy 2500Hd, PPEI tuned, CAT back exhaust, 2.5" Zone Level Kit, Moto Metal 970 wheels/Nitto Terra Grapler G2's, Custom Cab lights, LED Fogs, Resonator deleted
 
#20 ·
Yeah, I'm getting mixed signals from the dealerships. Just called one and they said a typical oil change was the mobile 1 delvac non synthetic 15w40. But that's one out of 4 dealerships. The others say full synthetic
 
#21 ·
Fwiw

For what is worth I will put my 2 cents in. I use Rotella T5 15w40 because I want the 15 weight oil here in the heat of S Louisiana. My oil/filter change interval is 5000 miles. I think that draining the contaminates in the oil sooner can do nothing but do my engine good. Some of my friends think I am wasting money. I think that oil is cheap and engines are expensive. Id rather change more often than necessary simply for my own piece of mind.

Im not suggesting you do anything , just saying.
 
#22 ·
For what is worth I will put my 2 cents in. I use Rotella T5 15w40 because I want the 15 weight oil here in the heat of S Louisiana. My oil/filter change interval is 5000 miles. I think that draining the contaminates in the oil sooner can do nothing but do my engine good. Some of my friends think I am wasting money. I think that oil is cheap and engines are expensive. Id rather change more often than necessary simply for my own piece of mind.

Im not suggesting you do anything , just saying.


Just my opinion but I think you are wasting money. I live in Baton Rouge, bought my '02 new 15 years ago and been doing 10k Mobil 1 5W-40 oil changes since the truck was about 1 year old. Before that I used Delvac because the Mobil 1 for turbo diesels wasn't available yet. Was changing the Delvac when the indicator said to - which was always 7,500 miles. Out of the 366k miles on my truck, probably 150k of them are towing and 100k of that is towing 10k lbs +. Other than injector problems (LB7) my motor hasn't been touched and runs awesome. Absolutely no signs of ring or bearing wear.
 
#24 ·
Lots of samples have been run on just about every oil on the market in these engines, general consensus is that they just don't care what you put in them. Wear numbers are pretty much identical regardless of conventional or synthetic, 5w-40, 15w-40, 10w-30 (at reasonable temps), these motors are just very very easy on oil. Any of them are more than capable of running 7500-10,000mi between changes.
 
#25 ·
OK here is the official word. I called up one the most highly rated Chevy service dealers in the Houston area and was told the oil they put in their new diesel trucks is a full synthetic 15w40. Oddly enough this seems to be the same story I get from every dealership however I ask them to forward me to the lube center manager. I asked the question again and he told me I don't believe it is synthetic let me go check with parts and ask. So he grabbed a bottle of the oil they use and it is indeed Mobile Delvac 15w40 non synthetic motor oil. Mystery solved.... finally.
 
#28 ·
I would not run any ck4 oil. Ford is voiding warranty for anyone that does, it is causing premature wear. Delvac is factory fill in duramax, you can still get delvac cj4, just make sure you read the label.


Sent from my iPhone using Tapatalk
 
#29 ·
It's not causing premature wear, it's just that they haven't been certified through Fords testing procedures yet. Cummins and Navistar have both approved CK4 and the new spec does have improved shear stability and a different additive package. Yes it has less zddp but it has others that have been added to make up the difference, the CK4 standard has been out there in development and testing for years (under the PC-11 heading). It's been proven have the same or better performance than what it has replaced and is fully backward compatible with CJ4 standards.
 
#31 ·
CK-4 is the new standard & it's fine to use/backwards compatible with CJ-4. Finding old stock of CJ-4 at stores isn't gonna be easy for long. This "what oil is best/use" is a overthought subject. For somebody new to the game just keep it simple.
 
#32 ·
No need to complicate matters. Valvoline Premium Blue and Pennzoil Long Life conventional oils in 15W40 are all you need. A 5W40 synthetic, as stated in the owner's manual is for operating in sub-zero conditions. I go to the local Ram truck dealers to get the oil changed as they carry one or both of these oils and the Valvoline Premium Blue conventional oil is what Cummins uses for its engines.

I suppose that the engineers and chemists at General Motors are idiots for recommending a 15W40 motor oil if you do not drive in sub-zero temperatures. What would they know? For my part I trust their people more than some yahoo at the quick lube place or a sales associate at the dealers.

Diesel fuel is very very dirty and some of it ends up in the engine oil so there is an inevitable buildup of soot and sludge. If you drive on the open highway with no heavy payload or towing a heavy trailer then a 10,000 mile change interval is fine. If you drive mostly around town or take short trips of less than 30 minutes duration then every 7500 miles is better. If you do tow heavy trailers all the time then every 5,000 miles is recommended.

It makes sense in particular when you see how much your miles per gallon varies with the type of driving you do. When towing or with a cabover camper in the bed my truck gets between 10 and 13 MPG depending upon the amount of headwind. Towing my 11,000 boat and trailer the truck averages around 13.5 MPG. Short trips around town and the truck averages 13 MPG. On the open highway with no payload and nothing in tow the truck averages over 17 MPG. There is a great deal of difference in the amount of fuel burned per mile driven as you can figure from these numbers.
 
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