Oil gone AWOL

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?

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.

Nad_Yvalhosert said:

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.

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I had thought of running thicker oil in the past, mainly to boost my oil pressure at idle up a little. Maybe next oil change I'll try some thicker dinosaur sauce.

I also put a bottle of Bar's stop leak in there too just to try. Figured it couldn't hurt. I haven't driven on it enough yet to "activate" yet though I don't think.

If you can, I’d drain out that stop leak asap. Usually not a good idea to run that stuff in anything.

No? Why's that? I haven't read into it at all (which is very uncharacteristic of me). But we use at my work from time to time and haven't heard any complaints from the bosses or anyone. However, we aren't exactly ASE certified where I work either.... So who knows lol

98chevy2500SS said:

If you can, I’d drain out that stop leak asap. Usually not a good idea to run that stuff in anything.

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Jerryred94silvy said:

No? Why's that? I haven't read into it at all (which is very uncharacteristic of me). But we use at my work from time to time and haven't heard any complaints from the bosses or anyone. However, we aren't exactly ASE certified where I work either.... So who knows lol

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I've been told that stop leak usually causes more harm than good in some scenarios, if left in a system for a long time. Our teacher tells us to avoid stop leak if possible lol.

98chevy2500SS said:

I've been told that stop leak usually causes more harm than good in some scenarios, if left in a system for a long time. Our teacher tells us to avoid stop leak if possible lol.

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Noted!

I use Quaker State high mileage formula 10w40 in the Burb. It seems to like it, doesn't use any until it's way due for a change (like after 3500--4000 miles since the last one). I also use AC PF1218 filters, since they meet all the factory specs for the vortec 5.7(350). On my old square body trucks, I could use a PF35, and on the 90 R2500 I could use the long 2 quart filter like the fleet models use. That 350 still looked good when I pulled the oil pan at close to 300 thou. Used straight 30wt QS in it, and the other 350s too. Regular grade, they didn't have the high mileage formula yet. On Dad's 06 Denali with the 6.0, I used QS 5w30 until we started having the oil pressure issue on startup. Switched to 10w30 and that helped.

Mechanic in a can is rarely a good idea.
The stop leak softens seals which leads to blown out seals. The theory is that a pliable seal is a happy seal which is true. What happens with stop leak is that the seal hardens over time and when the start to soften up they get too soft and can't seal. Minor cracks in the seal that were filled in by minor bits of sludge and were on a hard seal weren't ideal but they were rarely catastrophic. The stop leak then makes those minor cracks pliable and they rupture.

Nad_Yvalhosert said:

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.

Click to expand...

I'm wondering if the diesel oil had more detergent and possible cleaned gummed up oil control rings?