Try a different brand of oil and see if the usage changes. When I used Rotella synthetic, mine "used" between 1 and 2 qts. in 6000 miles. I switched to Mobil 1 and oil consumption went down by about half.
A lot less waas going out the crank case breather with the Mobil 1 as well.
Do you mean Delvac 5-40 or some type of 15-40? I'm not aware of Mobil 1 making a 15-40 Diesel oil in full synthetic 15-40--there's the 1300 Super 15-40 Dino oil.
Two things I'd suggest: Get an oil analysis done. That will tell you a lot of info and likely lead you in the direction of the problem.
Drill some small holes in your dipstick between the "bars." I had a really hard time getting consistent readings with the dipstick, so I drilled the holes and am much happier now.
Consider adding Lube Control 20. I AM NOT a fan of oil additives at all, and I was very suspect of this one too. I've given it a fair trial, and my minor oil consumption in my Dmax has decreased to almost nothing now. Oil analysis has noticeably improved with the use of LC20 so far. Time will tell the whole story...
My baby has 125,000 miles on her and never uses oil. The times the dealer changed oil I think they used delvac and when i change the oil i use rotella t synth. never any difference in usage and i change by the message center indicator.
I think GM goes by oil used per 100 gallons of fuel burned to determine whether
oil usage is acceptable. I thought it is up to one quart/100 gals. of fuel is normal. I wish I could put my finger on where i saw this.
I use Rotella Synthetic and if I fill mine to the top of the full mark on the stick, it will "find" it's way down to about half way and then hold that for as long as I want to go between changes...weird. don't think it burns the oil, but have no idea where that little bit goes either. seems to only be when using Rotella Synthetic too???
I use Rotella syn, no oil usage in 7500 to 8000 miles before change. Like any manufactered products there is a range of performance. You may be on the bottom of the range. I would be raising hell too,did this make sense to anyone?
I always used Mobil Delvac 1 synthetic 5W-40 until Mobil 1 Truck & SUV synthetic 5W-40 came out, and then switched to it. I change at 5000 miles and it is always at the full mark. Last summer when we went to Alaska, we left Ohio with fresh oil. I changed oil, filter and fuel filter in Fairbanks, and changed again when we returned to Ohio. Total 11,300 miles pulling a 10,000 lb 5th wheel, and both times oil level was still full.
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