3rd UOA, 07 GM 6.2L, 8600 mile, Mobil Delvac 1 ESP 5w30

Dec 15, 2010
San Antonio,TX
3rd UOA, 07 Yukon Denali Gas 6.2L, 8600 mile, Mobil Delvac 1 ESP 5w30

When this load of oil had 4000 miles on it, a plastic heater hose fitting broke. By the time I got off the hwy and pulled into a parking lot the temperature of the engine was quite HOT. I believe that is why the results are what they are.

Hindsight being 20/20, If something like this ever happens again, I'm going to change the oil immediately. Otherwise the results aren't too bad. Elevated aluminum and iron are probably from pistons, and cylinder walls/rings rubbing together when it got hot. Viscosity was starting to thicken. Virgin is 12, results are 13.2. TBN is at my personal minimum of 2.0. The lab, OAI, got the weight of this oil sample wrong, so the Baseline(BL) #s are wrong. So they flagged a few things that they shouldn't have. The sample I sent them, and the results are for, is 5w30, not 5w40 that is printed in the data at the top. In 2019 I sent them a virgin 5w40 sample, so that's what they used for a BL? The previous 2 loads of oil and reports were 5w40. I guess they didn't notice that this time I had switched to 5w30? I'll call them an get them to fix that.

I changed the oil and filters immediately after I pulled this sample. Usually I will wait to get the UOA results. The results usually indicate (to me) that the oil is good for another 1 or 2 thousand miles before it needs changing. Not this time. When I pulled this sample I thought the oil looked different/bad. I'm no expert but I've pulled a bunch of samples in the 10+ yrs that I've been doing UOA. When I cut the full flow filter open, I let the media gravity drip drain/dry for a week like I always do. But this time it stayed dark looking, almost black. If wouldn't turn the golden brown color like all my past Fram XG filters have done from my various vehicles. So this time I rinsed the media in Paint Thinner for a minute then let it drip drain/dry. The result is the bottom media in the picture below. The upper media is from the previous oil/filter change. Yes, I keep my old filter media in case something like this happens.

Here's some relevant data about the vehicle and oil:
I bought this vehicle used without any mx records 17 mths ago w/131k miles
Vehicle is stock, all aluminum non-AFM/DOD 380hp, 6.2L, L92
We use it mainly to drive back and forth between our two homes that are 1000 miles apart.
The engine had 157,200 miles and 4818 hrs since new when this sample was pulled.
The DIC info readout 25% remaining
This oil had 8600 miles and 184 hrs on it,
The vehicle consumed 524 gals of 89 octane unleaded since the oil was last changed
This time avg 16.4 mpg, last time it avg 15.7 mpg
This time avg 47 mph, last time it avg 45 mph
This time avg 2.86 gph, last time it avg 2.88 gph
The engine does not burn or leak any oil.
The catch can collected 1oz of liquid in these 8600 miles, last time also 1 oz

Here's a link from the last UOA that I did on this vehicle:

Again I installed 7 qts of Mobil Delvac 1 ESP 5w30, a Fram XG10575 full flow filter, and a Amsoil EaBP90 bypass filter.

What do ya think?


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Jul 3, 2005
Originally Posted by deven
Wonder what the numbers would be if you were using 0w20 oil and this happened..
My bet is they'd be worse, probably quite a bit worse. hide


$50 site donor 2023
Sep 21, 2010
Texas via IAH
Yep, my 2010 Z71 popped that fitting while towing my boat on a soft trail … engine hot message asap. Got rid of the fittings and just clamped to the aluminum nipples. Later I bought that hose harness and it was under the back seat when traded for 2018 Z71. Seeing an engine heat up so fast can change your thinking at the time … went from Mobil 1 10w30 to Delvac 15w40 since I was using that truck on/off road … probably wasn't necessary but it's a good inexpensive HDEO … Really the only thing to fail in 8 years of hard use … fortunately I carry clamps and water jugs in tool box. Unplanned coolant exchange when trip completed … but it was due really …
Dec 11, 2013
Manchester, England
Good work on finding an uprated aluminium part - plastic has its uses but its not as good as the heavier, more expensive metal altenative. These type of modifications for reliability are some of the most pleasing mods we can do to our cars smile
Dec 2, 2019
Originally Posted by jetman
GruvenParts.com makes billet aluminum replacements. That's what I went with. [Linked Image]
Still wish there was a "Like" button on this forum. Glad to see you went with the Gruven parts, Don, good choice.


Staff member
May 14, 2007
Indianapolis, IN
Overall I think this is a good example of a cautionary tale, but it's not a reason to panic or condemn the engine. - for those whom have this kind of event, always pull over as soon as safely practical - always change the oil and filter immediately upon service/repairs; don't finish the OCI out - don't worry; the engine will likely still be fine