8.1L Vortec Napa Gold 7099. Bits/grit

[Gasbuggy]

4 or 5000 miles/3 years (7.5 quarts). 2001 Silverado, 496 cube big block, has 150k on it. Was owned for a long time by an older man who ran Mobil 1 in 4k intervals. The truck lives a relatively easy life, minus some occasional romping. Gets 18 MPG. 8 city. 10 highway.

I was surprised to see bits and grit. There were several little shiny hard bits in the filter that were jagged and not magnetic.

This oil change was its first run of Mobil 1 15W50, and a 160 degree thermostat (and a bottle of MOS2) which surely is the grey goo. In the winter I drained a few quarts out (fumoto) and replaced it with plain Mobil 1 5w30. Thin the mix out for the cold.

The general consensus is Mobil 1 15W50 is safe to use and was the spec'd viscosity for the identical 8.1 used in marine applications. The 8.1 aluminum intake has a flawed pcv setup that sucks in oil vapor, the thicker oil and lower operating temp stops that. Otherwise, a quart every 1000ish miles will disappear.

It sits for 3-4 months without being started sometimes. Engine is always quiet, minus a little growling noise on any cold start, no tapping or ticking. Oil pressure is good/great.

Might send a sample after a couple thousand miles.

 

[bullwinkle]

Minus the metal bits, that's what the filter looks like on the Express in my sig. It's getting a much better oil than in it's past, RGT 5W30 & a quart of HPL Engine Cleaner 30 these days, hoping to flush some of those mountains of carbon out! Absent any crazy noises, not sure I would sweat that 8.1 too much, as long as the oil pressure is holding up OK & no bad sounds coming from it.

 

[JavierH19]

160f thermostat? that's pretty low. These iron blocks will live long lives at 210f. I have 340k on my yukons original 6.0 and almost 260k on my sierras 5.3 and neither have had head gaskets yet and I have overheated them both to almost 240f but that's not severe nor was it for long. With a 160f thermostat that 50 grade oil is way thicker. Honestly a 20 grade oil could be used because of the low oil temps from getting cooled to 160f which should make it comparable to almost a 40 grade with a 210f thermostat. I use 15w40 in both my old gas trucks.

 

[BrendanC]

i would put an OEM temp thermostat back in it. the computer will continuously be running the truck rich to try to compensate for low temperature. power enrichment won’t be there either.

 

[53' Stude]

4 or 5000 miles/3 years (7.5 quarts). 2001 Silverado, 496 cube big block, has 150k on it. Was owned for a long time by an older man who ran Mobil 1 in 4k intervals. The truck lives a relatively easy life, minus some occasional romping. Gets 18 MPG. 8 city. 10 highway.

I was surprised to see bits and grit. There were several little shiny hard bits in the filter that were jagged and not magnetic.

This oil change was its first run of Mobil 1 15W50, and a 160 degree thermostat (and a bottle of MOS2) which surely is the grey goo. In the winter I drained a few quarts out (fumoto) and replaced it with plain Mobil 1 5w30. Thin the mix out for the cold.

The general consensus is Mobil 1 15W50 is safe to use and was the spec'd viscosity for the identical 8.1 used in marine applications. The 8.1 aluminum intake has a flawed pcv setup that sucks in oil vapor, the thicker oil and lower operating temp stops that. Otherwise, a quart every 1000ish miles will disappear.

It sits for 3-4 months without being started sometimes. Engine is always quiet, minus a little growling noise on any cold start, no tapping or ticking. Oil pressure is good/great.

Might send a sample after a couple thousand miles.



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Nice truck! Thank You for posting. What oil filter went back on?

 

[Gasbuggy]

i would put an OEM temp thermostat back in it. the computer will continuously be running the truck rich to try to compensate for low temperature. power enrichment won’t be there either.

Maybe on other vehicles software but it exits open loop well before 160. I check the fuel economy regularly and it didn't change, I get 11.7-12.2, which is above average. It seems to run around 175, on a real hot day it will get up around 188-190. I have HP Tuners, I would adjust the tune before switching back and have it burning oil again.

Burns no oil now.

 

[Gasbuggy]

Nice truck! Thank You for posting. What oil filter went back on?

A free Purolator Boss.

 

[Gasbuggy]

160f thermostat? that's pretty low. These iron blocks will live long lives at 210f. I have 340k on my yukons original 6.0 and almost 260k on my sierras 5.3 and neither have had head gaskets yet and I have overheated them both to almost 240f but that's not severe nor was it for long. With a 160f thermostat that 50 grade oil is way thicker. Honestly a 20 grade oil could be used because of the low oil temps from getting cooled to 160f which should make it comparable to almost a 40 grade with a 210f thermostat. I use 15w40 in both my old gas trucks.

I bet the oil temps are closer to 200

 

[JavierH19]

I bet the oil temps are closer to 200

Peak oil temps closest to the crowns yes I agree but the lower thermostat temp keeps the sleeves cooler than normal and the average oil temp more close to water temp but usually a bit higher. But average oil temps are usually just a bit more than water temp.

 

[JavierH19]

Maybe on other vehicles software but it exits open loop well before 160. I check the fuel economy regularly and it didn't change, I get 11.7-12.2, which is above average. It seems to run around 175, on a real hot day it will get up around 188-190. I have HP Tuners, I would adjust the tune before switching back and have it burning oil again.

Burns no oil now.

That's not acceptable, perhaps look for an upgraded radiator. Even on hot days it should maintain temps better than that especially if you're not hauling. What water to antifreeze ratio are you using? I'd suggest using something like 70-65% water 30-35% antifreeze with an anti rust additive. For the antifreeze something like prestone platinum concentrate would be my go to. Water does a better job than the antifreeze at cooling. Before the factory radiator failed on my yukon at around 260k it struggled to keep temps down as well as it did before. Maybe yours is clogging. You could try to clean it but it normally doesn't do much. It may still have the original radiator.

 

[Gasbuggy]

Peak oil temps closest to the crowns yes I agree but the lower thermostat temp keeps the sleeves cooler than normal and the average oil temp more close to water temp but usually a bit higher. But average oil temps are usually just a bit more than water temp.

I've owned a handful of GM cars with oil temp sensors and consistently saw 20 degree or higher oil temp differences vs coolant temp. Oil temps also increase when running higher viscosity.

 

[Gasbuggy]

That's not acceptable, perhaps look for an upgraded radiator. Even on hot days it should maintain temps better than that especially if you're not hauling. What water to antifreeze ratio are you using? I'd suggest using something like 70-65% water 30-35% antifreeze with an anti rust additive. For the antifreeze something like prestone platinum concentrate would be my go to. Water does a better job than the antifreeze at cooling. Before the factory radiator failed on my yukon at around 260k it struggled to keep temps down as well as it did before. Maybe yours is clogging. You could try to clean it but it normally doesn't do much. It may still have the original radiator.

I suppose it's possible the gauge isn't accurate since this generation's gauge clusters don't have the best reputation. System doesn't seem to have any corrosion. Keep in mind it has a clutch fan that's not aware of lower thermostat so it's going to run warmer than the thermostat rating because fan engagement range hasn't changed and it's not assisting the cooling system.

I had a 160 is my L79 Chevelle SS and on a hot day it will also hit 180+ creeping along in traffic etc. Radiator is spotless inside. To me, in hot weather, this is normal behavior. Temps under 80, or continuously moving, different story.

 

[fantastic]

150k on the engine? Not horrible looking but noticeable stuff in the filter can.

 

[c502cid]

I run a 180* t-stat on my 8.1 with the EFI Live tune, based on their recommendations.

 

[Gasbuggy]

I run a 180* t-stat on my 8.1 with the EFI Live tune, based on their recommendations.

Any oil consumption?

 

[c502cid]

Any oil consumption?

Maybe a quart every 2500-3000 miles when working it, a quart every 4-5000 miles when not. My last 8.1 used a qt every 1500 miles no matter what and it was bone stock.

 

[Gasbuggy]

This thermostat questioning has me digging into what temp is really in there, and it may well be a 180 instead of a 160. I'm not sure why 160 stood out in my mind aside from having read so much forum conversation, it was swapped many years ago. I wanted to say 170 but that's not even available. Lower than stock either way and even on a hot day, if you're moving, it doesn't get past here. Blurry but it's 160 \ 210 / 260

 

[burbguy82]

This thermostat questioning has me digging into what temp is really in there, and it may well be a 180 instead of a 160. I'm not sure why 160 stood out in my mind aside from having read so much forum conversation, it was swapped many years ago. I wanted to say 170 but that's not even available. Lower than stock either way and even on a hot day, if you're moving, it doesn't get past here. Blurry but it's 160 \ 210 / 260

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Oh no, that would be way too cold assuming the gauge is working. The things needs to be hot, or at least hot enough and synced with the computer at that temp to be recognized as "warmed-up". Fuel trims will never be right. Unless you change the parameters in the computer. That bad boy should be right at 200-208 all day.

This oil change was its first run of Mobil 1 15W50, and a 160 degree thermostat

The general consensus is Mobil 1 15W50 is safe to use and was the spec'd viscosity for the identical 8.1 used in marine applications.

Or course, the boat engine is different than land based engine, and the use is different. You dont run around at 4000 rpms constantly do you? Only anaylsis can say that 15w50 works for your engine. Not sure I would go that thick. Point is, you have a couple of incompatible notions going on. May explain the black nasties in the filter.

nice looking truck

Change the thermostat back to factory, just run the AC delco filter. They are cheaper and just as good.

 

[350Rocket]

This thermostat questioning has me digging into what temp is really in there, and it may well be a 180 instead of a 160. I'm not sure why 160 stood out in my mind aside from having read so much forum conversation, it was swapped many years ago. I wanted to say 170 but that's not even available. Lower than stock either way and even on a hot day, if you're moving, it doesn't get past here. Blurry but it's 160 \ 210 / 260

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Can you get a cheap elm327 adaptor and use torque pro to get the actual number? That's what I do on my 2005 and it sits just below the middle but what I see digitally from the ECM is much more specific than the gauge.
I have a stock replacement 190 t stat and it runs about 192 mostly when moving...but it won't turn on the fans until over 230 if the AC is not on. The amount that the temp increases does not seem to be a accurately reflected by the gauge, it will look like it's just a hair over 210 when really it's 220-230. Maybe yours is like that or maybe it's the opposite.
My oil pressure gauge seems to be more accurate than the temp gauge.

 

[dlundblad]

The 8.1 in your truck vs an 8.1 in a boat at constant high RPM’s isn’t the same thing.

Use a 5w30 or a similar in viscosity 0w40. No need for aftermarket oil additives. Reinstall the OE thermostat.