I've been running Delo 5w-40 in my truck year around I tow in the summer with it also, I have zero complaints concerning any aspect of it.

 

I've always used the delo synthetic. I seem to remember reading somewhere that a study was done and they examined all the oils and all their ingredients, and that Delo had more boron (or some other element) in it that was beneficial to the engine. Kinda like what arch oil has in it. Don't know if it's true or not but that's why I started using it. Never had any problems. I get mine at Wally World. $20 a jug. My truck runs smooth and quiet. I do notice a big difference when I run Dino 15-40 (usually I'm tight on funds or they are out of the synth)

 

I looked up VOAs on several some years back: Delo 15w 40, the 5w 40 in question here, Rotella T6 and Delvac ESP. I've ended up running a blend of the two Delos and my truck loves it, but I live in a warmer climate too. Price on T6 had come down and I bought some on sale then returned it for the Delo 5w 40, I also buy mine at Walmart. I just changed the oil/filter in my FJR to it (was running the 15w 40) and it loves the stuff too -- shifts are smoother even when it is cold, something I wasn't expecting.

Here is my spreadsheet (sorry, I can't get the formatting to come out):

Delo 15W 40, Delo Synth, T6, Delvac 1 esp

Molybdenum 117, 38, 68, 1
Boron 679, 65, 70, 77
Calcium 1941, 791, 817, 774
Magnesium 516, 1243, 1176, 1054
Phosphorus 1312, 1122, 1157, 1054
Zinc 1490, 1179, 1310, 1259
TBN 8.79, 11.5, 10.94, 10.1
cSt Vis @ 100C 15.9, 14.16, 13.4, 14.56
Flashpoint 446, 420, 435, 415


The T6 and Delo synth look similar enough in their add-packs, but with synthetics, as I understand it, there is a lot more to the base oil construction than conventional oils. I liked how the conventional delo and the synth have somewhat complementary add-packs, that's why I went with those two for my blend.

 

I'm running the Delo 15w 40 and don't think my truck particularly likes it. I'm going to switch to some type of synthetic next OC, especially since I have stiction rearing it's ugly head.

 

Try adding Archoil along with it if not already

 

For the past 55 thousand miles I ran T6 5w40. The last oil change I sent out a sample of the T6 with 5,000 miles on it for testing. At the same time I switched to Delo Synthetic 5w40 for the cost savings. The results showed it is high in iron which the lab said may be from all the towing it does. Also the test showed the sample of T6 5w40 tested out as 5w30 viscosity.
So far I have about 1800 miles on it with no ill effects. I will be sending out a sample of this Delo once I hit 3000 miles for testing. I'll post my lab results of the T6 below, and follow up with the lab results of the Delo 400le at a later time, probably after my trip to SC and back towing the 12k fiver at the end of this month.

 

I have used T6 and delo. They are both fine. My experience is the T6 has better cold starting below about 35 degrees outside. Other than that, I would run either one.

 

I run the Delo 5w40 in my 03. No complaints here.

 

57 ppm iron isn't that high, it's nice to have it in the 20's but it's not at any warning level. It also could be the result of a contaminated sample if it was taken from the oil pan when you drained it. What caught my eye was the 6% fuel dilution. That could be adding to the viscosity drop IMO.

 

Great info here, thanks for posting.

This is were things get a bit tough to decide for 6.0L owners. As you can see in the sample comparison the additives are at similar levels for all the synthetics but higher for the conventional oils. That is because conventional oils hold the additives better than the synthetics. But the synthetics have the higher viscosity index. So what does a 6.0L owner choose? A 5-W40 to help fight of stiction and aid in cold starts or a 15W-40 with the stronger additive package and less shearing of the viscosity. That is where synthetic blends come in to play. You kinda get the best of both worlds.

T-6, Delo 400, Mobil & Schaeffer's all seem to hold up well to around 3-4 K miles, then the viscosity starts to tank. But in most samples I have seen for used oil in the 6.0L is that it hits a point and does not shear the viscosity any lower than 5W-30. Similar situation on 7.3L's running high ICP tunes over 3200 psi.

 

The is a spreadsheet from TeamRoper and some folks from The Diesel Garage floating around the web I need to try and find. Tons of 6.0L UOA analysis reports & graphs comparing various oils in the 6.0L. It was about 5-6 years ago, but it shouldn't be too hard to find.

 

Some of these samples look to be prior to the oil specification changed to CJ-4 that we now have. The Fed's limited the zinc to 1250 ppm and many of the oils have had to adjust the various additives to compensate.

 

Yeah the fuel dilution was my fault out of habit. While I'm under the truck and after I drain the oil I always empty the fuel filter drain in the same pan. I won't next time.

 

when you take the next sample make sure the bottom of the oil pan is clean and free from any rust that could contaminate the sample and give you a false high iron reading. Or grab one of these pumps for $20 to suck it out of the pan through the dipstick tube.

 

My pans are spotless. Also I have a Fumoto valve to draw the sample next time half way through the drain. The iron reading I believe is accurate. The fuel was the only issue like I explained. Thanks for the pointers though.