Ok to make custom Rotella blend?

[Black6spdZ]

I have an 07 Silverado Classic "LBZ" Duramax with 48k miles on the ticker now. Bought it when it had 20k and switched to Mobile TDT 5w-40 oil. Ran it for 10k miles, was about 3 quarts low even though this is in spec for oil consumption on these engines and had high copper count "oil cooler". At 30k did another Mobile TDT oil change, and ran it 10k miles same as first.. with same analysis and consumption results. At 40k I filled with Rotella T6 5w-40 and now at 48k it is getting close to the 3qt low just like the previous consumption pattern. Sooo.. my thoughts on the change coming up soon would be to fill with 5 quarts T5 15w-40 conventional and 5 quarts T6 5w-40 synthetic.. would this make something like a 10w-40 blend? I'm thinking a little thicker mix might help reduce consumption, add a little extra oil pressure and help my centrifuge work better

What are your thoughts?

 

[Colt45ws]

I dont see why not.

 

[JimPghPA]

I think you should check the oil level every 2K and top it off if required.

 

[FL_Rob]

3Qt in 10k is about as good as you're gonna get for now.Maybe in another 30k the break-in will be more complete and the consumption might drop alittle but time will tell.

Mixing those oils will still net you a 40 wt, at operating temp anyway,it wont hurt ..it just wont help either.

Maybe a Delo or Delvac would be worth a try.

 

[CourierDriver]

I would check ur degree in oil engineering first, but maybe ask the same question to
shell oil company and see what the oil maker says.

 

[dnewton3]

The official GM statement on oil consumption for the Dmax is 1 qrt per 100 gallons of fuel used.

My oil consumption is based much more upon load. During the winter/spring time, I use practically no oil in my Dmax. In the summer/fall (pulling the travel trailer at high speeds in heat) the consumption goes up, but still within the GM spec. (I actually see about 1 qrt per 125 gallons of fuel using dino 10w-30 HDEO).

As for the mix of oils, I'll say this: it won't hurt or help, most likely. And if you're only going to OCI every 10k miles, then any quality dino oil will suffice just as well for a LOT less money than synthetic, and still provide the wear and soot protection you desire. There are (by now) thousands of Dmax/dino UOAs to prove this point. You're spending one heck of a lot of money, and not really getting anything specific in return, even with your witch's brew ... Let's be honest here; you don't "need" synthetic (at least from what you've indicated). Ubber-Silly-Cold starts and extended OCIs are the only good reasons to use synthetics. It's not like cold starts are an issue in MS; you're not extending your OCI. Any dino 15w-40 will do very well.

If you're 100% convinced that you "need" a special oil, then consider the new T5 in 10w-40. It's cheaper than full syn's, and has that "special" viscosity you seek.

 

[dparm]

No, it will cause severe internal motor damage.

Kidding...mixing oils is totally safe.

 

[Jim Allen]

While blending is not generally harmful, especially if you are blending oils from the same manufacturer that uses generally the same (type) additives, I've never seen anything definitive that shows it's optimal a high percentage of the time.

My experience and observations make me doubt whether blending along the lines of what you propose would produce any change in consumption. Going to a heavier oil doesn't always (or often) reduce consumption in a basically "healthy" engine. Sometimes a thinner oil actually reduces consumption.

Anyway, if you do the experiment, you can tell us. The main thing is to be as scientific as possible and try to keep all the operational parameters the same as previous so you get an "apples-to-apples" comparison. Your consumption seems pretty consistent, so a change would be noticed. If the blend doesn't work, go the DNewton direction and try some 10W30 T5.

Everywhere I've looked, oil consumption seems pretty normal for the DMax, so you could be tilting at windmills here... but that's what we do here at BITOG, so you are fitting right in. Good luck and keep us posted no matter what you do.

 

[roadrunner1]

To add to the above posts, you could try a 10w-30 dino vs. a syn. blend. A syn blend or for that matter a syn isn't required in this application.

 

[JimPghPA]

Am I the only one who questions if by "Ran it for 10k miles, was about 3 quarts low" it was actually 3 quarts low, or they had added 3 quarts of toping off oil.

If you ran a sump 3 quarts low, you are making the remaining oil do more work than the engine builders had in mind. And there is the possibility that you could suck air into the oil pump. You would certainly not have the same amount of splash lubrication of the crank going on.

Again, I think you should check the oil level every 2K and top it off if required.

 

[Steve S]

Mix away .I would use 15w-40 MS = Mississippi? 5w isn't needed. To me 3 qts in 10,000 miles seems fine as it is is a big engine. You change your oil how often with a centrifuge bypass filter?

 

[Steve S]

Originally Posted By: JimPghPA
Am I the only one who questions if by "Ran it for 10k miles, was about 3 quarts low" it was actually 3 quarts low, or they had added 3 quarts of toping off oil.

If you ran a sump 3 quarts low, you are making the remaining oil do more work than the engine builders had in mind. And there is the possibility that you could suck air into the oil pump. You would certainly not have the same amount of splash lubrication of the crank going on.

Again, I think you should check the oil level every 2K and top it off if required.

Well first of all how much oil is needed fill when the add level on the dipstick to the full line? Anywhere between the two marks is safe to operate the engine and there are no modern engine designs that have splash lubing of the crank ,,, you are posting false info. The diesel engine holds how many qts of oil?

 

[citrustaco]

that's the mix I do when changing the oil on my irrigation pump's perkins motor

 

[dnewton3]

For the record, this OP has the Dmax; a normal OCI is 10 qrts at sump change.

Typically the dipstick range on a Dmax represents about 2 qrts change from low to high marks. To cycle three quarts would either mean he was a quart low, or he did top-off's along the way.

I always see the "top off" issue as one of interest. I typically don't top-off; my annual useage takes my Dmax sump from the high mark to the low mark over the whole year. If I were to add the two quarts along the way, it would do two things:
1) it would actually reduce my "ppm" counts (as it is now, my volume drop actually increases the concentration)
2) it would bolster the add-pack and alter viscosity
I don't add in oil unless I need it to keep from going below the safe range. When I UOA, I want to see how the "original" sump load performs as best it can without "sending in re-enforcements", so to speak. I would never endanger my expensive equipment, but I just like to see how things run without additional influence.

Most of us presume that when we say oil is low, that is measured from the "top" (full) mark on the stick. So, for the OP, I would have to presume he added some oil along the way, because to be three quarts low in a Dmax would be akin to running only 70% capacity; one quart below the safe range.

 

[Black6spdZ]

Thanks for the information everyone.. dnewton3, I had thought the hash marks on the stick were approximately 1qt per mark, if what you say is true then I am about the third hash down now at 8k miles "1.5qts"? Thats not bad at all. From all that I've read here I know I would be absolutely fine running dino oil.. at least a little synthetic gives me a little peace of mind and I can roll over at night and sleep better.. lol. I don't think my bypass centrifuge is doing much.. the LBZ dmax engine just doesn't run high enough oil pressure to spin it very fast. I had though about opening the the jet sizes a little larger to make it spin faster?

 

[dnewton3]

In my LBZ, the range between the upper and lower marks represent almost eactly 2 qrts. I only know that because I once did a top-off simply out of curiosity for that very topic. Generally, most people accept that the Dmax range represents 2 qts. However, each one will obvisouly be a bit different.

On my Dmax dipstick, there are little hash mark lines between the upper and lower limits. Those little hash marks do NOT represent a quart for each one. What I am trying to delineate is that from the "full" mark to the "add" mark represents approximately 2 qrts capacity. I have never tried to quantify what the little "in between" marks are worth in volume.

 

[Gene K]

T5 is 10W40.... Did you mean T3 15W40?

 

[dnewton3]

In the NA market:
T3 is 10w-30 or 15w-40
T5 is 10w-30 or 10w-40
T6 is 5w-40