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2500hd burns oil

buckmaster1995

By buckmaster1995
in Ask A GM Technician

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buckmaster1995 New Member

buckmaster1995

Posted
Posted

I have a 2001 gmc 2500hd with 275,000 miles. Lately it has been burning almost a quart of oil every 500 miles. And I noticed yesterday that it smokes on acceleration. what are some possible causes? Rings? Valves? Its got a lot of miles but has been taken care of extremely well. I've been told to put some Lucas in it. Any ideas?

00Silverado4x4 Senior Enthusiast

00Silverado4x4

Posted
Posted

Personally I put a can of engine restore in my vehicles. However with the miles you have it might worth tearing it down to replace worn parts. As you said it could be rings &/or valves. Just curious but what color smoke are you getting?

Jsdirt Senior Enthusiast

Jsdirt

Posted
Posted

Smoke under load is piston rings, no question about it. If you want that to go away, it's rebuild time (long block is the way to go there). Otherwise, drive it until it tosses a rod out the side.

 

Boy do I miss the days of .77 cent per quart oil ...

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

White smoke is usually steam, not smoke. Oil smoke is blue. You will get a more accurate view from following the truck as opposed to looking in the mirror.

 

As already posted, under load oil burning is usually rings. It can be either worn rings, or seized oil control rings. Oil burning on deceleration is usually valve seals or guides.

 

If you have worn rod bearings, that can also cause smoke on acceleration and deceleration by flooding the cylinder walls with more oil than the oil control rings can handle. This could also be the reason for seized oil control rings.

grampadirt Senior Enthusiast

grampadirt

Posted
Posted

White smoke could be a blown head gasket,do a compression check,that should lead you to your next step.

 

Smoke under load is piston rings, no question about it. If you want that to go away, it's rebuild time (long block is the way to go there). Otherwise, drive it until it tosses a rod out the side.

 

Boy do I miss the days of .77 cent per quart oil ...

Back when oil was 20,30,40,50 weights,none of this multi-weights like these days :lol:

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

Just to add some information to help interpret the results of a compression test when checking for a head gasket leak.

 

Generally a compression check will point out a head gasket when it is leaking between 2 cylinders. If it is leaking from coolant passage to cylinder it generally will not show on compression test until it is a severe leak. Once a head gasket starts to leak between 2 cylinders the engine will start idling rough. Engine idle roughness is also variable depending on which 2 cylinders have the head gasket leaking between them. On a GM 8 cylinder engine(firing order 18436572), cylinders 5 and 7 are next to each other in firing order, and in physical location. A head gasket leaking between those two cylinders will give a rougher idling engine than you would see when compared to the roughness from the head gasket leaking between cylinders 2 and 4

 

The engine in this case has only just started putting out white exhaust, and only under very specific conditions. I doubt a compression test will show anything unusual at this point.

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