Oil capacity???

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How do automobile manufacturers determine how many quarts of oil are necessary for a given engine?

I have a 1991 Chevrolet K1500 with 4.3 V6. Capacity is 5 quarts. My daughter has a 2002 Blazer with 4.3 V6. Capacity is 4.5 quarts.
 
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476
Location
North Carolina
How do automobile manufacturers determine how many quarts of oil are necessary for a given engine?

I have a 1991 Chevrolet K1500 with 4.3 V6. Capacity is 5 quarts. My daughter has a 2002 Blazer with 4.3 V6. Capacity is 4.5 quarts.
Look at the 2020 Hyundai Sonata owner's manual for the oil capacity for the 1.6 TGDI engine. Then look at the 2021 owner's manual for the same vehicle, same motor. Please consider that there are no physical changes to the engine between these two model years, they are identical. Then tell me what you think about how this manufacturer decided on the oil capacity for the 1.6 Turbo GDI engine. Thank you.
 

pbm

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Look at the 2020 Hyundai Sonata owner's manual for the oil capacity for the 1.6 TGDI engine. Then look at the 2021 owner's manual for the same vehicle, same motor. Please consider that there are no physical changes to the engine between these two model years, they are identical. Then tell me what you think about how this manufacturer decided on the oil capacity for the 1.6 Turbo GDI engine. Thank you.
I don't have those manuals handy...can you tell us the difference?
 
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476
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North Carolina
I don't have those manuals handy...can you tell us the difference?

Neither do I, but you can easily google both of them. That's why I said to search for them. The short of it is that for 2020 it's about 4.7 quarts and for 2021 it's 5.something. IIRC it's about 1/4 quart more.

The 2.4L Thetha II motor was initially specked for 4.7~4.8 quarts, then when fuel dillution on 5w-20 started killing motors they went to 5.07 and just changed dipstick color. Most Hyundai dealerships just put 6 quarts of oil in these motors as a preventive maintenance things. You can even go slightly above 6 quarts with a bigger oil filter. I run about 5.5 quarts of 0W-40 in mine and change it as often as I can, meaning at least twice a year or <= every 5000 miles.

The RAM 1500 5.7 HEMI can easily take 7.5 quarts of oil with the bigger SRT size oil filter, and will run just fine with 8 quarts. The more oil spare oil you have the better. Some of these came with bad oil dipsticks from the factory, and the oil pans are sized differently depending if the motor went into a Charger, Challenger, 300, RAM truck, JGC or Durango.

I assume that German and Japanese carmakers are way more precise with their oil capacities. I also owned Mitsubishi, Mazda and Ford vehicles and never had an issue with oil capacity. Hyundai and Doggie/RAM are a different story.

The bottom line is that some manufacturers take the time and precisely measure the oil capacity and correctly update the owners manual, while others like RAM/Dogde just type 7 quarts for the 5.7 no matter what configuration it is or model year. That's the definition of lazy. Just like the spec Mopar Transfer Case Fluid for the BW44-44. Good luck finding the correct fluid. I just use Amsoil because it covers all BW44-44 cases.
 
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If I was designing and had to or wanted to specify a thinner oil, I would increase the sump size and/or require a fancier (e.g. stay-in-grade) oil.
 
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476
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North Carolina
If I was designing and had to or wanted to specify a thinner oil, I would increase the sump size and/or require a fancier (e.g. stay-in-grade) oil.
Yesterday I was at our Hyundai dealer to do the annual inspection for my wife's Santa Fe. While there, I had a chance to look over the service manual for the 2.5 GDI and 1.6 TGDI Smartstream engines. When it came to allowed oil viscosities, both of them had the same viscosity/ambient temperature chart listing oil viscosities starting from 0W-20 and going all the way up to 20W-50. Then underneath that, there were detailed instructions for each engine about how to perform the oil change, remove the cartridge filter, torque spec for the drain bolt, and so on.

I guess that for all the pontificating and preaching that takes place on the Internet, we have to recognize the fact that not only are manufacturers designing and testing engines for a global market and multiple viscosities, but they know for a fact that a bunch of different oils will work just fine in their engines. The relationship between oil viscosity, ambient temperature, and outside conditions (desert versus tundra) still holds. The only disturbing thing is how blatantly many of them try to force and even lie to customers about using a certain viscosity in their engine. Hyundai has different allowed viscosities depending on what part of the world they are selling the vehicle. Toyota does the same thing. Chrysler/FCA/Stellantis (whatever they're calling themselves) lied to customers for years that MDS will not work properly if 5W-20 is not used, MS-6935 specifically, when in fact MDS works best with a healthy amount of oil pressure. Also, the MDS lifters are toast if one of the oil screens in a solenoid gets clogged up with debris, but that's a different story.

@OilUzer I believe that manufacturers have to push owners to use whatever oil they used during the EPA test cycle, at least in the US. I believe that countries in the EU are moving in the same direction regarding motor oil specifications. Protection against engine wear seemed to be a concern in Europe addressed by their multitude of beefed-up oils (HTHS above 3.5, Mid and Full SAPS, etc.). Now they run 0W-20 in small displacement turbos, just like we do.
 
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17,931
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NH
How many quarts are necessary?

Wild guess here, but it's probably tribal knowledge. I mean, an OEM doesn't just hire some recent grads and tells them to design a new engine. People on the teams have been doing this for years, and have done many tests over the years, and probably have reams of data going back years as to how their engines fare, in terms of oil temperature, bearing wear, and so forth. They can probably look at the desired specs for an engine and guess what the minimum amount of oil required will be, then work from there. Eventually it goes on a dyno and gets flogged, and if wrong, well, they either increase capacity or ask for a new oil spec.

That said, "How we've always done it" started someplace in past. Old engines needed more oil for various reasons. Like other things, sometimes what worked in the past gets copied forward, and either no one thinks about changing, or no one wants to put in the effort to change. 4 quarts versus 3, just how much effort would it require to test that out? Hours of dyno time isn't cheap.
 
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The right amount is enough to carry adequate heat out of the pistons/heads without heat soaking so bad it breaks down but no so much that the crank throws whip it up in a bubbly mess. Most engines are perfectly happy +- 1qt from the recommended amount, some are plenty happy with quite a bit more than that. If you want the max it can hold, figure out the sump and filter capacity and keep adding till you see foaming from the crank throws hitting the oil, or pull the pan and do some measuring then add for filter capacity and thermal expansion.
 
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Texas, USA
I've been trying to figure out why the Ford Coyote requires 10 quarts. Seems excessive. It would be a happy day if all the manufacturers could just settle on a 6.0 quart capacity, and then the oil companies would start producing a 6-quart jug.
 
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Location
Ohio
The oil sump/pan is one determining factor and you can't simply make it bigger in many cases. There may not be room. Also, there is going to be quite a big +/- value of what is "okay". Rounding comes into play too. Purely by the numbers, let's say they calculate 4.9 quarts as the median value - that's getting rounded up to 5.0 quarts in documentation (owner's manual, FSM, etc). Or, automakers are doing their designs in metric so that capacity of 4.8 quarts came from a nice, even value of 4.5 liters.
 
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1,278
I think there’s a lot of factors unblocked with oil capacity specifications.

The manufacturers oil change interval is probably a big one. The longer the suggested interval might mean a bigger sump and more oil to combat that longer interval. Same thing with a lighter weight oil recommendation. Someone here posted a formula of a comparison of wear between larger dumps and smaller ones. The oil molecules take less abuse, wear and tear if they are not being cycled through that engine as much in a larger capacity oil sump. And that equals longer drain intervals and oil life monitor length.

Fuel dilution and oil consumption. Direct injected engine with the potential of known fuel dilution from the manufacturer might mean more oil to combat a known problem that will arise. Same with oil consumption, give them a bigger sump and more oil. Christ, BMW used to tell their techs to overfill it by a quart (because they knew they drank oil and would be back with a low oil light). So who knows exactly? I’m sure they’re not going to tell us.
 

BlueOvalFitter

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The bottom line is that some manufacturers take the time and precisely measure the oil capacity and correctly update the owners manual, while others like RAM/Dogde just type 7 quarts for the 5.7 no matter what configuration it is or model year. That's the definition of lazy. Just like the spec Mopar Transfer Case Fluid for the BW44-44. Good luck finding the correct fluid. I just use Amsoil because it covers all BW44-44 cases.
Just like when some use the same oil filter for multiple oil changes. 😁
 
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