Oil gone AWOL

[Schurkey]

LOOK at the packaging for the oil.

Plenty of "diesel" oil is cross-rated for spark-ignition engines.

 

[Pinger]

Thicker oil. I run 10/40 on my trucks.
2 years ago, my '98 Suburban 2500 with its 5.7 lost 5/30 about the same rate as you. 3 quarts low after 1000 miles. Never a drop on the ground, barely any soot in the tailpipe.
Topped off with 5/30 and lost/burned another 3 quarts in 1000. Said screw it, and put in 15/40 diesel oil and was only 1 quart low 1000 miles later.

Next oil change went 10/40 and only put in 1.5 quarts over 3000. Slowing down the loss.
Next oil change went 10/40 again and only went 1 quart low by 3000.

Next 2 oil changes went with 10/40 and only 1/2 quart low at 3000 miles.
Gonna use 10/40 the rest of its life now.

That's my experience, for what it matters.

When it was getting through 3 qrts in 1000 miles did you ever look at the plugs? Did they show any sign of oil burning?

I made some interesting discoveries over the weekend. Mainly that there was a leak on the passenger side back corner of the intake and those two bolts on the intake around the water jacket were loose. Also, whoever assembled this motor used the rubber “seals” on the front and back of the intake. You know, the ones that are notorious for not sealing? Anyway. Pulled the intake off and I think I found out where the oil was going...

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Pretty sure those are s’posed to be dry. New gaskets are on though and we shall see what happens next.

Any update on this?
Did your plugs show any sign of oil burning?

 

[jjester6000]

I just did an oil change not even 300 miles ago and I’m already down a quart. No smoking from the tail pipe and the #1 spark plug looks normal, dry, like it’s running fine, no fouling. Additionally, I have not seen any new oil spots underneath the vehicle. So either it’s leaking somewhere and pooling up where I can’t see, or it’s being burned in the cylinders. Right?

I’m sick of this motor leaking all the time. It runs great and makes good power....but it won’t for very long if it keeps losing oil like this. What are y’all’s thoughts?

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1 quart every 300 miles is pretty good, my '74 GMC burns/leaks a quart of 20w50 every 30-40 miles (I'm putting a new motor into it soon).

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[Nad_Yvalhosert]

When it was getting through 3 qrts in 1000 miles did you ever look at the plugs? Did they show any sign of oil burning?

I did. Just a light brown tint to the porcelain, never a misfire, no sign of plugged converter either. And now that its permanently using 10/40 I have no loss of power. Fuel economy was never a consideration for a 6k lb truck, so getting 11 city, 12 highway, and 7 during the winter with my snow plow on is acceptable to me

 

[FarmerPhil]

What brand / weight oil do you use, just curious? I use pennzoil HM 10w/30 myself

 

[Pinger]

What brand / weight oil do you use, just curious? I use pennzoil HM 10w/30 myself

Using a 10W30.
New thread here >> https://www.gmt400.com/threads/vortec-5-7l-oil-consumption.51449/