NHTSA opens preliminary probe into more than 870,000 GM vehicles

[KMeloney]

I can’t wrap my head around the idea of not letting the truck warm up before driving it, especially when it’s cold out. My father insisted back in the ‘80s that I always let the car warm up, and that’s what I’ve always done.

 

[Antonm]

If warming a car up is causing an engine to fail in less than 30k miles I don’t think there is a fix.

I can’t wrap my head around the idea of not letting the truck warm up before driving it, especially when it’s cold out. My father insisted back in the ‘80s that I always let the car warm up, and that’s what I’ve always done.

The whole to warm-up or not to warm-up thing is about piston ring wear and not, repeat NOT, about bearing wear or bearing failure (which is what issue the 6.2 is having).

Back in post #258 I posted this video (linked again below). Fast forward it to the 29 minute mark and start watching from there. He does a pretty decent job of explaining the whole warm-up thing and using real data (and showing said data) from real engineers , not opinions of random internet personalities or wanna be influencers, but data from real engineers that published this data in peer reviewed industry publications.

...

 

[jfoj]

So I am going to have the state the obvious that seems to be getting over looked on a regular basis. Some people need to open their minds up and pay attention to real world operating conditions and not controlled lab situations or more ideal daily operation. Also understand how YOU operate your vehicle and WHERE your vehicle is operated will VARY GREATLY when compared to the way others operate their vehicle and where their vehicle is operated.

A few things that need to be cleared up that people are also missing. Engine oil temperature is actually more important than engine coolant temperature. Engine oil temperature typically takes twice as long to warm up than compared to engine coolant temperature. With a integral oil cooler in the radiator the engine oil will warm up slightly quicker than a configuration without a integral engine oil cooler in the radiator, BUT the thermostat needs to open to allow warm coolant into the radiator for this to happen. In some cases an integral oil cooler in the radiator will cause the engine oil to take slightly longer to fully warm up due to the additional oil capacity that is in the oil lines and oil cooler as well as the cold coolant will be soaking heat from the oil as it is trying to warm up before the engine thermostat opens. On these trucks with the integral engine oil cooler in the radiator, the oil still typically takes twice a long to warm up and catch up to close to the nominal engine coolant temperature.

So will excessive bearing wear happen from allowing the engine to warm up at an idle every day you own the vehicle, NO. Will the bearings wear more than if you started the engine and allowed it to run 30 seconds, then drive normally, YES. Just think about the engine run hours alone if you allowed the vehicle to idle 15 minutes before driving every start or many starts during the cold or warm weather. Every revolution the engine takes will cause component wear, so the less revolutions, the less wear.

So here is the spoiler that EVERYONE is missing. I think we can all agree that engines run Richer at idle than while cruising. With modern DI engines fuel dilution is a MAJOR problem. The problem varies a lot on how the vehicle is used. Remote starting or starting or even manually starting the engine and allowing the engine to idle to warm up or cool off the cabin for 10-15+ minutes, colder ambient temperatures are more problematic that warmer ambient temperatures, short in town trips, majority city driving, allowing the Auto Stop/Start feature to be enabled full time, extended idling at drive thru or car pool lines, stop and go traffic, DFM being enabled, towing and hauling heavy loads and so forth are hell on the engine oil. Keep in mind that fuel diluted oil will be consumed by the engine easier and quicker leading to the engine oil level dropping.

Many driver/owners these days are not manually checking the engine oil level on a regular basis. Check the engine oil at LEAST every 1000 miles max, or probably every other fill up would be wise habit. Not checking the engine oil manually then allows the engine to up running up to 2 quarts low on oil until the oil light comes on if the engine is consuming oil at a decent rate. 1 qt/1000 miles could mean you need to add 4-5+ quarts between oil changes. Part of the reason oil levels are not checked regularly, we have been conditioned with port fuel injected engines and modern design and assembly practices that led to a drop in oil consumption AND also many newer engines have done away with the dipstick! I often use the dipstick to check the oil level, look at the oil color and smell the oil for fuel. While I can’t determine the exact percentage of fuel in the oil with my nose, I can surely determine if the oil has a higher than expected fuel smell and/or a darker color that I do not like. In these cases I should probably change the oil sooner than some mileage window.

During the time the engine oil is low, the fuel concentration is likely higher, until you add 2 fresh quarts of oil, which then immediately drops the fuel concentration in the oil and if you add make up oil between oil changes, you are effectively diluting out the fuel percentage, this is a good thing, but if you are performing oil analysis at time of oil changes you may get a false sense of what is really going on in the crankcase. I hope the fuel dilution variation is obvious just by adding fresh make up oil.

Here is the other BIG spoiler, while the engine temp may be up to 160F, but understand the oil will likely only be at 80F. So all the lower end reciprocating components are still much, much cooler than the engine coolant temperature. Additionally the oil squirtters are bathing the bottom of the pistons and cylinder walls with colder engine oil that is approximately ½ the engine coolant temperature.

Let’s not forget the engine cooling system has a thermostat, that limits the flow of warmer coolant into radiator, so even if the engine has an integral engine oil cooler in the radiator, the engine oil cooler is not getting bathed in warm coolant until AFTER the thermostat opens and even when some thermostats open, they cycle a few times Open/Closed before the engine coolant temperature stabilizes at a nominal operating temperature.

So again, the engine oil cooler is actually in the wrong location to some extent to be helpful for cold start operation. I have seen engine oil coolers that are hybrid air/coolant coolers that circulate the engine coolant while the thermostat is still closed, in this case for cold start operations, this becomes an “oil warmer”.

Some may say, well when I changed my oil, I had an oil analysis performed and the fuel dilution was in the low range and acceptable. This is good, BUT, understand over the lifespan that the oil is in the engine, the fuel dilution percentage can change and become lower as some of the fuel is “cooked off” during longer highway cruises and fresh make up oil being aded. But the opposite can also occur, some operating conditions can actually increase the fuel contamination as well.

Here is the catch; the percentage of fuel in the oil can and will vary over the lifetime that the oil is in the engine (meaning between each change interval). A lot depends on outside ambient temperatures, the colder the temps, the greater the fuel contamination. Then factor in all the non ideal usage of the vehicle and other variables. Longer highway drives likely will cook off fuel in the crankcase at a higher percentage maybe getting the oil back in the “acceptable” range along with adding make up oil.

Few will likely agree with me on this issue. Engine coolant temperature is a false indicator of when the engine is fully warmed up. Engines warm up much faster when driven than when sitting at idle and the engine is not running as rich a fuel mixture when the engine is under light to moderate load then when at idle. Fuel concentration in the engine oil is a moving target, depending on how the vehicle is used can impact the amount of fuel in the oil drastically.

All I can say, is you do you. You do what you believe in. But one fact is clean oil is better than dirty oil and oil is far cheaper than replacing internal metal parts in an engine. Modern DI gasoline engines are very different animals from the days of carburetors, throttle body injection and port fuel injection. How the foolish oil companies and oil filter suppliers are pushing 10,000-20,000+ mileages with their products and some people are buying into this nonsense. I have no plans on testing how long I can push my OCI or allow the engine to “warm up” before driving, because I understand what is actually going to happen to the engine oil and the engine in the long run and it is not pretty.

Starting with a 0W20 oil that is likely borderline for this engine due to the High Torque/Low RPM operations, add fuel to the oil, run the engine low on oil, do you really think this will allow these engines to get to 250,000 miles? There are just a few steps each of use and owners can do to extend the life of any engine. Common sense oil maintenance is what needs to be considered.

 

[nomech]

The testing of engines after being built is called "Cold Testing" where a large electric motor is used to sping the engine at different RPM's and look for specific parameters. They can monitor the torque required turn the engine, the airflow thru the engine, monitor for noise and vibrations and so forth. I and not sure if GM used the Spintron or something similar.

Except forf the few broken connecting rods and broken or wedged pistons, the majority the problems are all bearings failing and/or spinning. The bearing supplier issue should have sailed in 2021 or by mid 2022. But we are here in early 2025 and still seeing the 2023 and 2024 models with problems. Waiting on the first 2025 problems to surface soon.

Seems to be a subset that fail before the first oil change, typically before 7500 miles, a few in the 10,000-15,000 window then again in the 25,000-35,000 window. Not sure what is really causing the different failure windows.

I really belive the 6.2l is a perfect storm of a number of problems. Some based on design choices, some due to the programming of the ECM/TCM, some are on how the vehiles are loaded and used, some are problems caused (I have to be careful with this term, but I do ot have a better one) by how the vehicle is used buy the owner, what fuel they put in the tank, how much remote starting or allowing the egine to warm up without driving, oil change intervals which are typically following the OLM, but in many cases this is too late for how the vehicle is being used.

The 6.2l behaves like a Diesel and is put under tremdous Torque loading at Low RPM. On the highway most of these engines do not turn more than 1700-1800 RPM, the transmission rarely downshifts. The bearings may be getting beat out of these engines?

Seems that every one of the bottom end failures is pretty much caused by lack of lubrication, not enough lubrication or contaminated lubrication.

I am going to go out on an limb and call what is going to happen with this NHTSA investigation.

I could be very wrong about this, but here it goes:

GM is either going to somehow show the numbers are not that high or that the problems have all occurred and they are now tapering down to a safe and managable number.

I do not expect there to be a recall where engines are replaced.

I expect that GM will have a recall offering a software solution to hardware failures. They will also probably print up some updated requirements or reinforced requirments that may not have been followed by owners regularly.

1. GM will REQUIRE the 6.2l to use Preminum fuel
2. GM will suggest that then engines not be remote started or started and allow to idle to warm up
3. GM will instruct that the engine oil be checked ever 3rd to 4th fill up and topped off, not waiting until the low oil light is illuminated
4. GM will likely extend the engine warranty to 10 years/150,000 miles
5. GM will likely reprogram the OLM for a shorter oil change intervals
6. GM will likely reporgram the 2 stage oil pump to either run at full pressure all the time, or switch the 2nd higher pressure stage on earlier and under specific circumstances, like when the oil pressure drops to 20 PSI or lower.
7. GM will likely reprogram the oil pressure warning to come on when the oil pressure drops to a specific low level or possibly have a low pressure trend that triggers a dash warning that indicates there is a low oil pressure situation and you should exit the road.
8. GM will likely implement a "Limp Mode" if the oil pressure drops to a dangerously low value to hopefully allow the vehicle to be pulled off the road before the engine siezess.
9. GM may reconfigure/recalibrate the towing mode, most likely alter transission shift points, may limit the top 1-3 gears, may alter the oil pump stage tirgger point when towing. May even state the engine oil be changed after towing or implement some torque counter that adjust the oil change interval
10. GM may make a change on the oil requirement for either daily driving and/or towing

So we shall see what and when anything happens. I expect that I may be correct on some of the action GM will take. I am not expecting any answers until late 2025 or early 2026. So if you own a 6.2l I would not hold my breath for a great and permenant solution.

Number 2 is a bummer, I live in cold climate area and I remote start my 2020 tahoe all the time when it is cold out. They might as well remove the remote start feature from the 6.2s if remote start will cause issues.

 

[jfoj]

The remote start by itself is not really the problem, it is starting the engine, especially in the Winter time and allowing the cabin to warm up/windows to thaw out and so forth.

I use the remote start as I walk out to the vehicle so it the engine has been running 15-30 seconds before I put the vehicle in gear to drive off. Just saves me a few seconds waiting in the cabin.

Any sort of extended idle on a DI engine is asking for some form of fuel dilution of the oil.

Every time a new technology comes out, it is usually 10+ years when you can look back and say maybe we should not have listened to the marketing hype and done some things differently.

I think the guys are a bit more in tune to what you should and should not do with anyting mechanical. Hand the truck over to the wife to haul kids, it becomes nothing but a utility item or commadity, why does she need to understand how anything works. Push a button on the remote, the engine starts and the car gets warmer or cooler, if the oil gets low, a light tells me, oil needs to be changed a light tells me, forgot to put gas in the tank a light tells me. If the motor fails at 4,000k or 40,000k chances are you get the "look" that means its time to move on and spend more money. Tell me you have never been there!

Even fuel type and blend plays into the problem. Colder climate fuels tend to be oxygenated during the colder time of year and if you are not careful or depending on where you live, 15% Ethonal is now the norm, not for me. Better be running premium fuel in anything that has a 6.2l as well.

 

[Vladimir2306]

So I am going to have the state the obvious that seems to be getting over looked on a regular basis. Some people need to open their minds up and pay attention to real world operating conditions and not controlled lab situations or more ideal daily operation. Also understand how YOU operate your vehicle and WHERE your vehicle is operated will VARY GREATLY when compared to the way others operate their vehicle and where their vehicle is operated.

A few things that need to be cleared up that people are also missing. Engine oil temperature is actually more important than engine coolant temperature. Engine oil temperature typically takes twice as long to warm up than compared to engine coolant temperature. With a integral oil cooler in the radiator the engine oil will warm up slightly quicker than a configuration without a integral engine oil cooler in the radiator, BUT the thermostat needs to open to allow warm coolant into the radiator for this to happen. In some cases an integral oil cooler in the radiator will cause the engine oil to take slightly longer to fully warm up due to the additional oil capacity that is in the oil lines and oil cooler as well as the cold coolant will be soaking heat from the oil as it is trying to warm up before the engine thermostat opens. On these trucks with the integral engine oil cooler in the radiator, the oil still typically takes twice a long to warm up and catch up to close to the nominal engine coolant temperature.

So will excessive bearing wear happen from allowing the engine to warm up at an idle every day you own the vehicle, NO. Will the bearings wear more than if you started the engine and allowed it to run 30 seconds, then drive normally, YES. Just think about the engine run hours alone if you allowed the vehicle to idle 15 minutes before driving every start or many starts during the cold or warm weather. Every revolution the engine takes will cause component wear, so the less revolutions, the less wear.

So here is the spoiler that EVERYONE is missing. I think we can all agree that engines run Richer at idle than while cruising. With modern DI engines fuel dilution is a MAJOR problem. The problem varies a lot on how the vehicle is used. Remote starting or starting or even manually starting the engine and allowing the engine to idle to warm up or cool off the cabin for 10-15+ minutes, colder ambient temperatures are more problematic that warmer ambient temperatures, short in town trips, majority city driving, allowing the Auto Stop/Start feature to be enabled full time, extended idling at drive thru or car pool lines, stop and go traffic, DFM being enabled, towing and hauling heavy loads and so forth are hell on the engine oil. Keep in mind that fuel diluted oil will be consumed by the engine easier and quicker leading to the engine oil level dropping.

Many driver/owners these days are not manually checking the engine oil level on a regular basis. Check the engine oil at LEAST every 1000 miles max, or probably every other fill up would be wise habit. Not checking the engine oil manually then allows the engine to up running up to 2 quarts low on oil until the oil light comes on if the engine is consuming oil at a decent rate. 1 qt/1000 miles could mean you need to add 4-5+ quarts between oil changes. Part of the reason oil levels are not checked regularly, we have been conditioned with port fuel injected engines and modern design and assembly practices that led to a drop in oil consumption AND also many newer engines have done away with the dipstick! I often use the dipstick to check the oil level, look at the oil color and smell the oil for fuel. While I can’t determine the exact percentage of fuel in the oil with my nose, I can surely determine if the oil has a higher than expected fuel smell and/or a darker color that I do not like. In these cases I should probably change the oil sooner than some mileage window.

During the time the engine oil is low, the fuel concentration is likely higher, until you add 2 fresh quarts of oil, which then immediately drops the fuel concentration in the oil and if you add make up oil between oil changes, you are effectively diluting out the fuel percentage, this is a good thing, but if you are performing oil analysis at time of oil changes you may get a false sense of what is really going on in the crankcase. I hope the fuel dilution variation is obvious just by adding fresh make up oil.

Here is the other BIG spoiler, while the engine temp may be up to 160F, but understand the oil will likely only be at 80F. So all the lower end reciprocating components are still much, much cooler than the engine coolant temperature. Additionally the oil squirtters are bathing the bottom of the pistons and cylinder walls with colder engine oil that is approximately ½ the engine coolant temperature.

Let’s not forget the engine cooling system has a thermostat, that limits the flow of warmer coolant into radiator, so even if the engine has an integral engine oil cooler in the radiator, the engine oil cooler is not getting bathed in warm coolant until AFTER the thermostat opens and even when some thermostats open, they cycle a few times Open/Closed before the engine coolant temperature stabilizes at a nominal operating temperature.

So again, the engine oil cooler is actually in the wrong location to some extent to be helpful for cold start operation. I have seen engine oil coolers that are hybrid air/coolant coolers that circulate the engine coolant while the thermostat is still closed, in this case for cold start operations, this becomes an “oil warmer”.

Some may say, well when I changed my oil, I had an oil analysis performed and the fuel dilution was in the low range and acceptable. This is good, BUT, understand over the lifespan that the oil is in the engine, the fuel dilution percentage can change and become lower as some of the fuel is “cooked off” during longer highway cruises and fresh make up oil being aded. But the opposite can also occur, some operating conditions can actually increase the fuel contamination as well.

Here is the catch; the percentage of fuel in the oil can and will vary over the lifetime that the oil is in the engine (meaning between each change interval). A lot depends on outside ambient temperatures, the colder the temps, the greater the fuel contamination. Then factor in all the non ideal usage of the vehicle and other variables. Longer highway drives likely will cook off fuel in the crankcase at a higher percentage maybe getting the oil back in the “acceptable” range along with adding make up oil.

Few will likely agree with me on this issue. Engine coolant temperature is a false indicator of when the engine is fully warmed up. Engines warm up much faster when driven than when sitting at idle and the engine is not running as rich a fuel mixture when the engine is under light to moderate load then when at idle. Fuel concentration in the engine oil is a moving target, depending on how the vehicle is used can impact the amount of fuel in the oil drastically.

All I can say, is you do you. You do what you believe in. But one fact is clean oil is better than dirty oil and oil is far cheaper than replacing internal metal parts in an engine. Modern DI gasoline engines are very different animals from the days of carburetors, throttle body injection and port fuel injection. How the foolish oil companies and oil filter suppliers are pushing 10,000-20,000+ mileages with their products and some people are buying into this nonsense. I have no plans on testing how long I can push my OCI or allow the engine to “warm up” before driving, because I understand what is actually going to happen to the engine oil and the engine in the long run and it is not pretty.

Starting with a 0W20 oil that is likely borderline for this engine due to the High Torque/Low RPM operations, add fuel to the oil, run the engine low on oil, do you really think this will allow these engines to get to 250,000 miles? There are just a few steps each of use and owners can do to extend the life of any engine. Common sense oil maintenance is what needs to be considered.

This is not true at all, the temperature of the oil in the engine warms up faster than the coolant, and it is always hotter than the coolant. Because the oil is in direct contact with the piston, and its task is precisely to remove heat from the hottest spot of the engine. In often tm in T1, the temperature of the coolant is about 91-93C, and the oil temperature is 110-115C

 

[jfoj]

This is not true at all, the temperature of the oil in the engine warms up faster than the coolant, and it is always hotter than the coolant. Because the oil is in direct contact with the piston, and its task is precisely to remove heat from the hottest spot of the engine. In often tm in T1, the temperature of the coolant is about 91-93C, and the oil temperature is 110-115C

And you know this because you have MONITORED it on numerous different makes and models with data acquisition devices? I have for years.

Why don't you cold start your vehicle and monitor the Engine Coolant Temp va Oil Temp and come back and tell me this is NOT true at all!

Keep in mind the engine coolant is in a closed loop circulation mostly in the engine and heater system, but the engine oil is not seperated into a closed loop circulation until a specific temperature is reached. A lot of the engine coolant heat on cold start more than likely comes from the cylinder head becasue of the exhaust gasses passing out the exhaust ports and the piston is constantly being cooled by much colder oil from the crankcase and oil squirtters.

 

[Stbentoak]

If I had an engine that ate two quarts of oil between oil changes, I would consider it defective and would ditch it pretty dang quickly.
I don't think I've ever owned an engine that I've had to add more than 1/2 a Qt. to between changes, if anything.

 

[jfoj]

1 qt per 1000 miles has been the automotive industry "Acceptable" consumption for years, not sure if they have dropped it? But lets say you are changing oil per the OLM (Approx 7500 miles) on a gasoline 5.3l or 6.2l. Seems that usually for the first 2000 miles, minimal oil consumption, then it often hits this 1 qt per 1000 miles, usually due to fuel dilution in the oil. Count this up, this would be closer to 4 quarts per oil change, you likely would not add the last quart because you would just say screw it, the oil needs to be changed anyway.

 

[blanchard7684]

And you know this because you have MONITORED it on numerous different makes and models with data acquisition devices? I have for years.

Why don't you cold start your vehicle and monitor the Engine Coolant Temp va Oil Temp and come back and tell me this is NOT true at all!

Keep in mind the engine coolant is in a closed loop circulation mostly in the engine and heater system, but the engine oil is not seperated into a closed loop circulation until a specific temperature is reached. A lot of the engine coolant heat on cold start more than likely comes from the cylinder head becasue of the exhaust gasses passing out the exhaust ports and the piston is constantly being cooled by much colder oil from the crankcase and oil squirtters.

I see this asked alot in other forums and it does seem as though the oil temp lags coolant temp.

Coolant is running through the water jackets and the cylinder head passages which is clearly a huge amount of surface area vs bearings and oil wetted surfaces.

Water/coolant does have about twice the heat capacity of oil, but it has 4 times the conductivity.

Makes sense!