10w30 mixed with 15w40

[simplistic]

I've got 2 gal of t-5 and 1/2 gal of delvac 15w40 from left over changes. What harm would it do if i mixed the two items together in my durmax? Would it make a heavy 30wt? I would hate to have two buy more oil since both are rated for my applaction.

Does anyone see a problem with this?

 

[AITG]

That should be the equivalent of an 11W32. If you look around BITOG I'll bet you can find someone who swears by it.

In reality, the Duramax is one of the most forgiving engines out there. As long as both oils are the proper rating (and they are), you should be fine.

Of course, this is the internet. YMMV, don't try this at home, professional driver, closed course, etc. etc.

 

[dnewton3]

Absolutely no issue whatsoever mixing them; they are both approved for use in the Dmax.

That engine simply does not care what you use as long as it's a properly qualified HDEO.

Why not try and and have a little fun? Run a UOA after a full OCI and prove it to be safe!

 

[A_Harman]

T5 is already a heavy 30 weight. Adding 20% 40 weight to it will probably put it right on the dividing line or make it a light 40. Shouldn't be a problem.

 

[userfriendly]

I blend 10W30 and 15W40 together all the time and not just with the Duramax (2 of them) so it must be ok.
I don't worry if the 10W30 and the 15W40 are the same brand either.
The days of lubricants of the same application, type, and class fighting with each other are within reason, history.
If that statement was not true of motor oils, service stations would have to carry every brand imaginable or the owners would have to carry extra oil that is in their engines.
Fear factor is what keeps some people from blending oils of different grades and brands.
Maybe for the fun of it I'll blend 6 different oils together and put the concoction in a 2013 5.3L Chev 1500 pick up.
One liter will be a TO-4 SAE 50 transmission oil for good measure. I'll shoot for a 5W40 or there about.
The UOA I bet will prove that nothing much matters, and if anything matters,it won't be by much.