Got rid of the diesel sound on my 2007 denali

[Brian Wilson]

I had low oil pressure and my truck sounded like a diesel at any temp. I switched to 5 quarts of 5w30 full synthetic and a Purolator pro filter. And added a full quart of marvel mystery oil and a cup of Trans fluid. The diesel clatter went away almost instantly. During the first drive down the street. Maybe 3 miles? Changed the oil again after 500 miles and the oil was very dirty. New filter and 6 quarts of 5w30 full synthetic again and now my oil pressure is much better and no clatter. Even when cold. The previous owner told me he used 15w 30 in the truck to keep the clatter down. Sad it would help. Probably caused the problem. I suspect the low oil pressure was due to going way too long without an oil change

 

[STORMIN08]

I would suspect that the AFM has some effect on the noise...it allows oil build up intothe lifter bores.


The 07 Yukon XL that injust traded starting the noises at about 80,000 miles...i started running HOT SHOTS SECRET for power stroke diesels...it cleaned it up nicely.

Only down fall, was it still used oil.

 

[MichaelSE]

What does the Marvel Mystery Oil do?

 

[M3kanic]

I recently had to replace the vram because of a stuck silonoid in it. I am pretty sure it was from bad oil. I am the third owner of my Denali. The first owner dealer maintained it up until 60k and I'm not sure what the second owner did, but when I pulled the valve covers the where stained brown with oil. Since I have put full synthetic and half of bottle of sea foam and that oil change came out really black so hopefully that helped.

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[StockHoe]

I too had the clicking noise. I'm not sure if it is piston slap or bad lifters. I read about Marvel Mystery oil. I took out a quart of oil and put in the MMO and it sounds like it is running a lot better. Since putting in the MMO I have not had the noise. I guess we will never really know what is in this stuff but it seems to work.