2004 Buick Lesabre 3800 SII L36 engine. Did upper and lower intake manifold gaskets with the aluminum frame lower gaskets and upgraded upper manifold at 50k miles. Did as precaution because the upper manifold was leaking oil and previous owner never changed the coolant.
Have run Pennzoil Platinum 5w30 since I bought it but it uses quite a bit of oil with that. At least a quart in 3k miles. Before a long trip recently I checked the oil and it was down a full quart, and there was some yellowish milkyness under the oil fill cap. It was a 6 hour round trip on the highway pulling a 5x8 utility trailer. The engine was run a bit hard under those circumstances because I did anywhere from 55, 60, to 65mph, a lot of that in 3rd gear rather than overdrive, and the stupid ramp on the back of the trailer acts as a sail. It makes a huge difference from 50mph folded up versus folded inside the trailer, but it's gotta be up while hauling a motorcycle.
The color under the gas cap after the trip was black so I must have burned off whatever was in there.
Full size image of oil cap
I'm thinking it is most likely coolant but would like to hear from the 3800 experts. Could my head gaskets be leaking coolant into the oil? I am on my first change to Pennzoil dino yellow bottle 5w30 since then and it uses noticeably less oil. I also wonder if letting the oil go down a quart or more is related as well.
I also noticed that the gasket that came with my intake plenum had the little injection mold nubs literally on the gasket seating surface where it seats with the lower intake manifold. It looked pretty stupid to me but I'm not an auto mechanic so what do I know. Do all the upper intake gaskets have injection mold nubs on it's seating surface?
This is the intake manifold I used. http://www.ineedparts.com/gm-intake-sure-fix-manifold-kit.html
Thanks
Have run Pennzoil Platinum 5w30 since I bought it but it uses quite a bit of oil with that. At least a quart in 3k miles. Before a long trip recently I checked the oil and it was down a full quart, and there was some yellowish milkyness under the oil fill cap. It was a 6 hour round trip on the highway pulling a 5x8 utility trailer. The engine was run a bit hard under those circumstances because I did anywhere from 55, 60, to 65mph, a lot of that in 3rd gear rather than overdrive, and the stupid ramp on the back of the trailer acts as a sail. It makes a huge difference from 50mph folded up versus folded inside the trailer, but it's gotta be up while hauling a motorcycle.
The color under the gas cap after the trip was black so I must have burned off whatever was in there.
Full size image of oil cap
I'm thinking it is most likely coolant but would like to hear from the 3800 experts. Could my head gaskets be leaking coolant into the oil? I am on my first change to Pennzoil dino yellow bottle 5w30 since then and it uses noticeably less oil. I also wonder if letting the oil go down a quart or more is related as well.
I also noticed that the gasket that came with my intake plenum had the little injection mold nubs literally on the gasket seating surface where it seats with the lower intake manifold. It looked pretty stupid to me but I'm not an auto mechanic so what do I know. Do all the upper intake gaskets have injection mold nubs on it's seating surface?
This is the intake manifold I used. http://www.ineedparts.com/gm-intake-sure-fix-manifold-kit.html
Thanks
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