How do OEM's decide oil capacity?

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I've been wondering about this for awhile now. How come engine size and oil capacity are not linear? Look at these oil capacities and give me your thoughts: Explorer 4.0 v6 - 5 quarts Escape 3.0 v6 - 6 quarts How come the larger, more powerful Explorer v6 holds a full quart less than the smaller Escape v6?
 
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I think the real answer is simply that it doesn't matter too much. A V-6 can go 4-7k with a 4.5 quart sump just as easily as a 4 cyl can go 4-7k with a 6 quart sump. So in the long run ( no pun intended ) it's a non-issue.
 
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I know that with nissan when I worked for them the difference was mainly due to the overall size of the engine package, the engineers come up with the minimum acceptable capacity for a given engine and then size/fitment dictated the size of the oil pan, different cross members and front diffs had to be taken into account as it is cheaper to have one size for all aplications.
 
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Well, the Colonge-built 4.0 is a old engine, from a time of shorter OCI and 10w30 oils. The Duratec 3.0 is a more modern engine designed around thinner oils and longer OCI. (and more tolerance from owner neglect)...just guessing here.
 

KW

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 Originally Posted By: law3500
I know that with nissan when I worked for them the difference was mainly due to the overall size of the engine package, the engineers come up with the minimum acceptable capacity for a given engine and then size/fitment dictated the size of the oil pan, different cross members and front diffs had to be taken into account as it is cheaper to have one size for all aplications.
What he said.
 
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In the development of the 5.7 Liter LS1 for the 1997-2004 Corvette, they had a problem with oil starvation under high g turns and on a skidpad. They developed an oil pan with "batwings" and baffles that was 6.5 quarts. Later, with the next generation (2005-?) Corvette, they solved this problem with a smaller, more conventional oil pan.
 

mva

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BMW's typically hold 7 quarts. The larger sump allows for improved cooling and longer oil change intervals.
 
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Well, "improved cooling" can also mean "insufficient heating". Obviously an infinite sized sump would never work. A NASCAR-sized sump of 15 quarts won't work well either if you don't get up to self-cleaning temps on your run to get Lottery tickets. Low OP temp will also affect final visc too. So, like most things, it's a balancing act. OCI length ultimately has little to do with it, imo.
 
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Do smaller engines typically work harder than their larger displacement counterparts? For example, does an I-4 engine have to work harder than a V6 or V8 to get up to speed?
 
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I think displacement has to be a big factor: most 1.6L I know has only 3 qt capacity. The odd balls like Toyota/Lexus direct injection V6, even the 2.5, get 6.6 qt probably because of fuel dilution or the potential of running in high stress temperature that cause sludge in the earlier 3.0 V6. Overall I think the design target a reasonable 5k-7.5k OCI, and size the sump accordingly.
 
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My 3.4L V6 toyota holds 5.6 qrts 2.4L I5 volvo holds 6.0 qrts I think 6.0 qrts is a lot for 2.4L I still change oil every 6 months with synthetic.
 
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 Originally Posted By: LOLVO
My 3.4L V6 toyota holds 5.6 qrts 2.4L I5 volvo holds 6.0 qrts I think 6.0 qrts is a lot for 2.4L I still change oil every 6 months with synthetic.
Depending upon the miles driven and the conditions encountered you may be defeating the advantage of syn oil.
 
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