Why not a 2 quart oil capacity for a engine?

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MI
Just been wondering... so most of the time people are so paranoid about 3000 mile oil changes when the oil has alot of life left.. don't you think car manufacteres should have a engine that takes only 2 quarts of oil or maybe just 3 with a oversized quality oil filter. I think so.. My car takes 4 quarts of oil... i think it can do well using maybe 2.5 quarts if I do a couple of modifications like smaller oil sump etc..
 
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The more oil, the better and longer life you'll get out of it. Smaller the sump, the shorter the OCI will be. Most large domestic V8's and BMW/Benzs' all have 7-8 qt sump capacities and can easily hit 10-15k miles drains. I would NEVER want a 2 qt sump.
 
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MA
It would be something only the thriftiest of people might want to do. I know Nissan oil changes usually take less than 4 quarts, they are probably thinking along the same lines as you are, K_R.
 
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There has to be an optimum size for each engine. Too big and it takes too long for the oil to warm up (of course with the thin oils specified these days, maybe that is no longer a problem). Too small a sump and I would expect the oil could overheat. Want to run Redline in your 2 quart sump? It should handle the heat.
 

Korean_redneck

Thread starter
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889
Location
MI
quote:
Originally posted by buster: The more oil, the better and longer life you'll get out of it. Smaller the sump, the shorter the OCI will be. Most large domestic V8's and BMW/Benzs' all have 7-8 qt sump capacities and can easily hit 10-15k miles drains. I would NEVER want a 2 qt sump.
This is exactly my point. People are paranoid and do Shorter OCI regardless(3k intervals). even the ones with large sumps,, they still change at 3k. Porsche Owners still do 3k oil changes even though the manual saids 15k. you see? this would be better for the enviroment.
 
Some manufacturers also change the oil capacity in different vehicles with identical engines. I've always assumed this is due to the service that the vehicle will potentially see, but is could also be due to the availablity of room for a bigger oil pan. example: Ford 5.0L in the Mustang, CrownVic, F150, and Explorer.
 
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The sump has to have some reserve capacity for high RPM use and hard cornering/braking. At high RPM, there's more oil up in the engine and during cornering/braking, oil with slosh away from the pump pickup. So you might get by with a 2 quart sump while cruising down the hiway, but under extreme conditions, it would cause problems.
 
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ME
VW Bug. (old style aircooled): 2 qts 20w50. No filter on most of them either, just a screen.
 
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Western Washington
quote:
Originally posted by Korean_redneck: you see? this would be better for the enviroment.
Shhhhh!! If the EPA hears someone suggest that something is better for the environment, they'll make it into law in a matter of days, regardless of whether or not its a good idea!
 

Patman

Staff member
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I'm surprised nobody mentioned this yet, but what happens when that engine begins burning oil? Then when it goes a quart low, it's danger time!
 
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More fuel for the fire: If you have been following Cathy Covington's story in another forum in this web site, consider what would be happening if oil sumps were half the size. I guess what I am saying is: How many failed engines would it take to offset the savings in reduced oil usage? If you were the manufacturer, does this sound like a smart move?
 
My Nissan Sentra takes 2 7/8 qts. with a filter change. I'm running 5K intervals (UOA proven) and don't seem to have any problems. It's very economical as oil changes cost only $5-$6. With 68K miles it burns about a 1/2 quart per 5000 miles (did so since new). Patman's comment about the oil level is correct though...you have to be more diligent checking the oil level as being a quart low in the Sentra is much different then being a quart low in a F-150 or similar big V-8.
 
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On the old 50hp or so VWs you could guess the age of the vehicle from the thickness of the sludge, kind of like aging horses by the wear of the teeth. As I recall a 'fancy VW' like a flat 6 Porsche has something like a 12 to 13 qt sump.
 
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The 911 Porsche has a dry sump holding the bulk of the oil. I remember one year had a outside flap like the gas flap and some people got confused and put gas in the oil tank.
 
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Houston, Texas
quote:
Originally posted by eljefino: VW Bug. (old style aircooled): 2 qts 20w50. No filter on most of them either, just a screen.
I had those engines in my old dune buggies. With only a 2 qt capacity I was constantly checking the oil for fear of running low.
 
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Most engines with a 5 quart sump could run on 4 quarts with little problem. However, the margin of safety for temp and low oil level goes away. The selected sump sizes are a comprimise between need and safey. [Big Grin]
 
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quote:
Originally posted by Ugly3: Most engines with a 5 quart sump could run on 4 quarts with little problem. However, the margin of safety for temp and low oil level goes away. The selected sump sizes are a comprimise between need and safey. [Big Grin]
and you may notice that on those engines, the dipstick has (often) 1 qt between Full and Add, meaning that the "correct" level is anywhere between the marks, not just at Full. the minimum level is 4 qts with a 1 qt buffer.
 
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Toronto, Canada
I am just not sure what a small sump accomplishes. Saves $5 in oil per change? To me that's hardly worth the hassle. I would be concerned about 2 things. The ability of a low volume of oil to contain contaminants. This would be addressable by UOA, but most people don't do UOAs. Also you would have to spend $20 on a UOA to tell you whether saving $5 on oil was a good idea. The other issue is what others have cited as the lack of saftey margin. My 3.0L engine consumes oil. It however has a 7 quart sump. The oil light comes on when it is down 0.5 quart. the lower end of the dipstick is about 6 quarts. Its pretty idiot proof, if somewhat alarming. Given the size of reserve and the warning indicators, I don't see how anyone would let it get dangerously low. On a 2 quart sump, you are walking that tightrope all the time.
 
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quote:
Originally posted by peterr: I am just not sure what a small sump accomplishes. Saves $5 in oil per change? To me that's hardly worth the hassle. I would be concerned about 2 things. The ability of a low volume of oil to contain contaminants. This would be addressable by UOA, but most people don't do UOAs. Also you would have to spend $20 on a UOA to tell you whether saving $5 on oil was a good idea. The other issue is what others have cited as the lack of saftey margin. My 3.0L engine consumes oil. It however has a 7 quart sump. The oil light comes on when it is down 0.5 quart. the lower end of the dipstick is about 6 quarts. Its pretty idiot proof, if somewhat alarming. Given the size of reserve and the warning indicators, I don't see how anyone would let it get dangerously low. On a 2 quart sump, you are walking that tightrope all the time.
good point. To me (an engineer with 25+ years experience) a good design ANTICIPATES things that may go wrong and above all, easily antcipated human failures. A too-small sump is flirting with disaster and I would give it a poor rating on design for reliability.
 
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