So after reading a thread on here about oils i decided to trying synthetic oil in my 01 2500HD. Thread said i might see better mileage, less oil consumption as ...

So after reading a thread on here about oils i decided to trying synthetic oil in my 01 2500HD. Thread said i might see better mileage, less oil consumption as these engines are know for, and greater engine life.

Havent seen better mileage, not really a big deal. However, the oil consumption went the wrong way!! I have had the check engine oil light come on now twice since going to the synthetic and i havent even put 2,000 miles on yet. There are no leaks any where that i can see. I am not happy!!

I was using Mobil Super 5000 oil before. I put Shell Rotella Gas Truck synthetic in now. Any ideas?

Truck has always used a bit more oil than i think it should but never to this degree. Also, found the air intake tube was loose from the throttle body(stupid aftermarket thing that was on it when i bought it and it dont stay tight) Could that have caused an issue, not totally sure how long it has been loose like that.

If the motor was sucking in unfiltered air for a long time, it could accelerate engine wear and eventually cause excessive oil consumption. How many miles are on the motor?

In engines that have used mineral oils, frequent oil filter changes will often correct increased oil consumption. Once engine deposits disappear, oil consumption rates should return to normal or lower than normal rates providing there are no mechanical problems.

I believe those engines had the fixed orifice PVC valve on the valve cover. There's a baffle underneath with some breather holes in it. If the holes get clogged, will cause excessive oil to get sucked through PVC system. I have heard this, although I've never had an issue on my lowly 4.8 (same design). Might be worth investigating, though.

On a side note, the only time I've ever had the "oil level low" light come on was in my commuter car, Buick Lesabre. And I had indeed used synthetic (Mobil 1). I switched back to dino. The damn 3.8 in that car will outlast the trans anyway lol.

GBSierraSLE wrote:If the motor was sucking in unfiltered air for a long time, it could accelerate engine wear and eventually cause excessive oil consumption. How many miles are on the motor?

I figured that was possible but this was extemely fast change.

has 120,xxx miles

Scrapyard John wrote:I believe those engines had the fixed orifice PVC valve on the valve cover. There's a baffle underneath with some breather holes in it. If the holes get clogged, will cause excessive oil to get sucked through PVC system. I have heard this, although I've never had an issue on my lowly 4.8 (same design). Might be worth investigating, though.

On a side note, the only time I've ever had the "oil level low" light come on was in my commuter car, Buick Lesabre. And I had indeed used synthetic (Mobil 1). I switched back to dino. The damn 3.8 in that car will outlast the trans anyway lol.

How do you fix that/clean the PVC valve?