2022 L8T 6.6 Oil Use Calculation (when to worry and when not to)

[UltimateToolReviews]

So I wanted to closely monitor my oil use in this truck, since it's the only real issue with this engine anyone talks about and hopefully put some people at ease. I've owned other HD gas trucks and they all use some amount of oil, especially when working hard, it's normal for any brand. Here is the math I did

 

Oil change at 46900, put in 8.4 quarts on propose, to get to the top of the cross hatch, exactly 8 quarts will only get you the middle of the cross hatches on the dip stick. 

Checked oil at 49350, so 2450 miles driven under mixed loads, towing 12k, hauling 2-4k in the bed, highway at 70-80mph and lots of city driving in hot FL, but little idle. 

Dipstick was at 1/2 cross hatch, added 0.4 quarts exactly to bring it back to the top, wanted an exact read on how much it used.

 

That comes out to 0.16 quarts used per 1000 miles or 0.000163 quarts per mile. I do my oil changes at 3000-5000 miles. To get the oil low message on the dash you need to be 2-3 quarts low, which if you do a 8.4 quart change you would need to drive around 17,000 miles on my truck. Not something I would ever do. 

So if your checking and changing your oil like you should, 3000-5000 miles and doing the math on any oil use you can figure out pretty quick if your L8T is having oil issues. This oil use is right on my par with my 2019 6.4 Hemi, nothing unusual for an HD gas truck that works. Also I use Kirkland oil from Costco and filters from Walmart. 

 

[Pryme]

I can confirm 8 quarts get to mid point on cross hatches. Mine seems to just stay there though. But I also have never had more than a few thousand pounds in tow. And don’t beat my vehicles. I think my truck has been up near redline 1 or 2 times ever. 

[Chuck FB]

5 hours ago, UltimateToolReviews said:

So I wanted to closely monitor my oil use in this truck, since it's the only real issue with this engine anyone talks about and hopefully put some people at ease. I've owned other HD gas trucks and they all use some amount of oil, especially when working hard, it's normal for any brand. Here is the math I did

 

Oil change at 46900, put in 8.4 quarts on propose, to get to the top of the cross hatch, exactly 8 quarts will only get you the middle of the cross hatches on the dip stick. 

Checked oil at 49350, so 2450 miles driven under mixed loads, towing 12k, hauling 2-4k in the bed, highway at 70-80mph and lots of city driving in hot FL, but little idle. 

Dipstick was at 1/2 cross hatch, added 0.4 quarts exactly to bring it back to the top, wanted an exact read on how much it used.

 

That comes out to 0.16 quarts used per 1000 miles or 0.000163 quarts per mile. I do my oil changes at 3000-5000 miles. To get the oil low message on the dash you need to be 2-3 quarts low, which if you do a 8.4 quart change you would need to drive around 17,000 miles on my truck. Not something I would ever do. 

So if your checking and changing your oil like you should, 3000-5000 miles and doing the math on any oil use you can figure out pretty quick if your L8T is having oil issues. This oil use is right on my par with my 2019 6.4 Hemi, nothing unusual for an HD gas truck that works. Also I use Kirkland oil from Costco and filters from Walmart. 

 

 

So following that theme you laid out of your particular truck under both its load and ambient temp operating conditions, have you continued that same use case out to 5000 miles and observed its total use. The reason I ask is that over the years I have noted often with vehicles and equipment, the first number of hours or miles within an oil change the engine is not using much oil but as the use continues the oil consumption rate ramps up very noticeably which to me at least would indicate a breaking down of the oil in sheer or additives ( and combustion contamination building ) or for that matter its possible that fuel dilution is playing a part in it. Figured I would ask and see what you've observed. 

 

My L8T, I haven't driven it far enough on an oil change to have given it a fair shot to see if it will show signs of oil use yet ( or unreasonable oil use as all engines use something, its a matter of how much ) as the last oil change I had 1750 miles or so on it and no perceptible usage so at least a good sign, also have not been towing with it so it was not not under a high load either. 

 

The other item I found interesting and I see Pryme has found the same thing with his truck as per what the oil sump holds going by the dip stick and assuming going by the markings on an oil jug to determine oil volume poured in. So far my oil changes are not showing that much oil being required and I wonder what is different as I go through the variables that could cause the difference in oil volume. What I have experience so far is that when I add exactly 8 quarts going by the markings on the jugs of the oil brand I am using, I am over the full mark so that its just climbed up at the full round section of the dipstick. How much in volume that would be, I would guess at least .1 or maybe .15 of a quart too much above the full mark. I am using the Delco filter as per oil volume it holds and I allow it to drain for at least a half an hour if not an hour and the engine was warmed up mostly but not actually driven for a distance so that the oil was boiling hot but plenty warm. So in my mind now as I sit here wondering about this and why mine seems to be different ( yes the book does say 8 quarts ), did I not leave it drain long enough although I find that hard to believe. Is my truck sitting at a different attitude as it is on an almost flat floor but there is a slight slope on that floor to the rear of the truck of about a 1/2 inch so the front would be slightly higher than if the floor was perfectly flat. I raised the front of the truck slightly beyond the stock factory setting by about a 1/2 inch and within that leveled the truck from side to side as it had a fair lean to the drivers side when first bought ( ironically a lean to the drivers side would probably allow more oil to go into the engine for the dip stick to show full ). Is my dipstick length different or my dipstick tube or how its inserted into the block. My other thought is that what if the oil volume in the jugs of oil that people are using are not exactly what they say they are and varying by brand or batch, I am currently using Mobil oil and even though in Canada, they package them as 4.73 liters / 5 US quarts and I dump in one full one and go down to the 2 quart mark on the second one. I start the engine once I have added all the oil and let it run for at least a minute, shut it down and leave it sit for a while and check the oil level initially and see its plenty full, then recheck it many hours or the next day to confirm when the oil is cold. Perhaps its because I am located closer to Santa's house and am on some strange tilt LOL, anyone have any other idea's ?.Like I said, just seemed so close to the factory listed volume and thought yes this all makes sense, until I saw your two comments today and wonder what is different as we are talking half a quart different.

 

 

Edited December 6, 2025 by Chuck FB

[Another JR]

When you are doing this kind of monitoring, remember that 8 quarts at 70F expands to 8 and 1/3 quarts at 180F. 

[Pryme]

6 hours ago, Another JR said:

When you are doing this kind of monitoring, remember that 8 quarts at 70F expands to 8 and 1/3 quarts at 180F. 

I actually didn’t realize it would be that much. So if he overfills it from the beginning it might be a bit too full when heated up? Something to think about I would say. 

[MORSNO]

1 hour ago, Pryme said:

I actually didn’t realize it would be that much. So if he overfills it from the beginning it might be a bit too full when heated up? Something to think about I would say. 

 

The top of the cross hatch area is full cold, so it should not be an issue, and I agree not to overfill. 

[UltimateToolReviews]

Only checking in the morning cold and in the same parking spot, so no issues there. Not worried about overfill on these huge v8s, you can overfill probably 2 quarts and not see any issues. These aren't BMWs.