GM 3.9L Oil Capacity

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I've acquired a 2010 Buick Lucerne with 34000 miles on it. Great ride. But can someone explain how or why they designed this engine to only take 4 quarts of oil? Really? That just doesn't seem like much especially if you are following the oil life monitor which can sometimes extend drain intervals.
 
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Jan 22, 2011
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The tiny oil filter accounts for a small reduction in capacity, maybe half a quart. Today's oil is much improved over the oils which were available for the older, larger capacity engines of the past. It is what it is, I wouldn't lose any sleep over it.
 
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Originally Posted by Mark72
I've acquired a 2010 Buick Lucerne with 34000 miles on it. Great ride. But can someone explain how or why they designed this engine to only take 4 quarts of oil? Really? That just doesn't seem like much especially if you are following the oil life monitor which can sometimes extend drain intervals.
My 84' Pontiac held 3-1/2 quarts with the filter. It managed to reach 300k before dying of rust. I always bought name-brand oil and changed it every 3k. But the filters I chose for it were economy priced Puro Classics or Orange Can. That dipstick never read more than a half-quart low. Use good oil and keep the dipstick level at full. Sleep well.
 
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Oct 16, 2019
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GM engineers figured this out for you already. Just run a quality synthetic and change it at reasonable intervals and the sump capacity will never be the death of the car. The GM 3900 3.9 V6 was GM's replacement for the 3.8 V6. This engine was designed from the beginning to be more efficient and eco friendly compared to the 3.8. In trying to achieve those goals GM gave it cylinder deactivation and a smaller oil sump. As it turned out the 3.9 V6 is not fuel efficient and not powerful enough to justify its existence. The 5.3 V8 FWD setup got the same or better mileage than the 3.9 V6 so there was no point to continue its production. I had a couple rental Impala LTZ's with the 3.9 V6 in 2007 or 2008 and they got terrible mileage. I remember getting 22MPG highway on those.
 
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I should disclaim this real quick, the 3.9 is EPA rated for faily decent MPG highway, but that is with cylinder deactivation activated. My experience with these engines is anything north of 65mph the engine stays in V6 mode and they suck gas.
 
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Originally Posted by buddylpal
I should disclaim this real quick, the 3.9 is EPA rated for faily decent MPG highway, but that is with cylinder deactivation activated. My experience with these engines is anything north of 65mph the engine stays in V6 mode and they suck gas.
The 3.9 was designed to work with the system in place. Once the government changed the speed on the highway portion of the MPG Test and it became a detriment to meeting CAFE numbers it's days were numbered. Wonder if the Chinese still make it? PS At least that's the way I recall it.
 
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My mom's old Corolla 4-cylinder held just over 3 quarts and had a teeny filter. It ran like a champ forever and it was not treated kindly. I really don't think sump size is something that the owner should try to re-engineer. Remember that the oil life monitors on modern vehicles consider many different factors. As stated, use quality oil, keep it in the proper range on the dipstick and change it on time... you will very likely have no trouble related to the oil.
 
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