Extended OCIs = Oil Capacity?

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523
Location
Illinois, USA
Is it safe to say that if 2 identical engines have 2 different motor oil capacities (like one engine holds 4 qts. of oil and the other holds 6 qts. of oil) that the one with the greatest capacity offers the longest OCI? It would seem to me that this would be true. I suppose the engines would have to identical though.
 

Patman

Staff member
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22,000
Location
Guelph, Ontario
Definitely! In the case of my LS1 Corvette, the factory specified capacity is 6.5 quarts, but you can safely run 7.5 without a problem. I am able to run a longer OCI with better results at 7.5 than I would if I only ran 6.5.
 
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4,844
Location
Saskatchewan
Yes. The high capacities of heavy-duty engines are what allow them such long intervals. Another example is the 5.9L Cummins in Dodge trucks, which uses a 13L capacity to get its 8,000 mile severe service interval. Provided the filter is up to the job, doubling the oil capacity should double the OCI.
 
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2,338
Location
Charlotte Metro area
I think that would be true, except in situations where the oil doesn't get hot. Short trips with cool oil are nasty after a while due to fuel not being burned off...so bigger sumps would only magnify the problem, right?
 
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5,722
Location
Charlotte, NC
I've been thinking about this for a while. When I finish the A-RX rinse on my beater, (91 Dodge Spirit 2.5l), which is driven locally, 2-3 times a week, about 3K/year, I think I'll run it one qt. low and see how it goes.
 
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260
Location
Newtown, PA
quote:
Originally posted by Patman: Definitely! In the case of my LS1 Corvette, the factory specified capacity is 6.5 quarts, but you can safely run 7.5 without a problem. I am able to run a longer OCI with better results at 7.5 than I would if I only ran 6.5.
Pardon my ignorance, but where does it go? An extra quart would be great for my oil raping saab.
 
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39,805
Location
Pottstown, PA
It depends on the profile of your pan. The LSI probably has high rpm windage accounted for in the pan clearances/depth. If you aren't on the track, you could probably run a quart over without creating problems (obviously you can). Same with my Caravan. I could probably go two quarts over. I've got a deep pan and the crank can't hit the sump. Your Saab may be able to do it too. I'd just be careful if you've got a MAX overfill mark on your dipstick. This became necessary for some engines due to lowering profiles of the car ..and centralized bulk oil systems that overfilled no matter what the operator/technician dialed in.
 
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6,902
Location
Louisiana
quote:
Originally posted by Raven18940:
quote:
Originally posted by Patman: Definitely! In the case of my LS1 Corvette, the factory specified capacity is 6.5 quarts, but you can safely run 7.5 without a problem. I am able to run a longer OCI with better results at 7.5 than I would if I only ran 6.5.
Pardon my ignorance, but where does it go? An extra quart would be great for my oil raping saab.

How handy! [Big Grin]
 
Messages
260
Location
Newtown, PA
quote:
Originally posted by BrianWC:
quote:
Originally posted by Raven18940:
quote:
Originally posted by Patman: Definitely! In the case of my LS1 Corvette, the factory specified capacity is 6.5 quarts, but you can safely run 7.5 without a problem. I am able to run a longer OCI with better results at 7.5 than I would if I only ran 6.5.
Pardon my ignorance, but where does it go? An extra quart would be great for my oil raping saab.

How handy! [Big Grin]

[Embarrassed] Was hoping you wouldn't see that. **** I admit it, I want to get an OCI over 4K. You're a follow saaber, you know if there's any extra room in the sump? The problem is if the max accounts for high rpm windage then I'm done cause I rev the **** out of my car quite often.
 
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651
Location
la jolla, ca
I think that's partially why German engines are known to last a long time. A lot of the 6 cylinder MBZ/BMW engines take 6-8 quarts of oil. Also probably designed to have more oil for that hard driving at high speeds. On the other hand the Nissan VG33E held 3.5 quarts yet were well known for longevity, granted used in different manners.
 

Buford T. Justice

Thread starter
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523
Location
Illinois, USA
I am curious with what engine and oil capacity Mobil 1 EP was based to last 15,000. Surely not a 4 cylinder with 3.5 qts. of oil. But it would make sense that the fact there is more oil that there is more additives and protectants in the oil.
 
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1,904
Location
Canada
Oil oxidation (the main limiter in OCI extension) is an Arrhenius-type process, whereby the reaction rate increases exponentially with increases in temperature. Thus, even minute reductions in lubricant temperature, can extend oil life significantly. As rpn453 points out, doubling oil volume should at *least* double oil life. Actually, oil life should be more than doubled by doubling oil volume. Inversely, if you cut the amount of oil in half, the life would be more than halved.
 
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5,785
Location
Dixie
OCI = (C*)(sump-qts)(mpg)(cubic inches/Hp) Where C* is an emperically derived constant.... All things being equal, increasing your sump capacity by 50% will allow you to increase your service intervals by at least that much. The added benefit from larger sumps is a moderation of peak oil temps,which will reduce the rates of oxidation & nitration. In other words, the oil will degrade slower chemically as well as physically. As an aside, I'd typically use a C* of 40 for conventional oils, a C* of 80 for most off the shelf synthetics and a C* of 120-150 for the best ACEA A3/B4 or A5/B5 rated, PAO and/or Ester based synlubes. TS
 
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12,385
Location
Northern CA
quote:
Originally posted by TooSlick: OCI = (C*)(sump-qts)(mpg)(cubic inches/Hp) Where C* is an emperically derived constant.... All things being equal, increasing your sump capacity by 50% will allow you to increase your service intervals by at least that much. The added benefit from larger sumps is a moderation of peak oil temps,which will reduce the rates of oxidation & nitration. In other words, the oil will degrade slower chemically as well as physically. As an aside, I'd typically use a C* of 40 for conventional oils, a C* of 80 for most off the shelf synthetics and a C* of 120-150 for the best ACEA A3/B4 or A5/B5 rated, PAO and/or Ester based synlubes. TS
Too Slick, you're making it too complicated. Your formula is based on gallons of fuel used, tossing in MPG just obfuscates the relationships. Peal away the uncessary complication and what your equation says is: Change oil at: Gallons of fuel burned = (CxSump capacity in qts x in^3/hp) which gives exactly the same results as using mpg in your original formula and is more direct. Plug in some numbers and try it. Take C=80, Sump Capacity = 5.5 qts, in^3/HP = 0.91 Simple way. Gallons of fuel burned = 80 x 5.5 x .91 = 400.4 Complicated way. Miles = 80 x 5.5 x 26 x .91 = 11410.4 miles 10410.4 miles/26 mpg = 400.4 gallons. Both methods of calculation have you change oil at the same distance and same amount of fuel burned Plug in any MPG you want for the combination I gave, and the answer still comes out change at 400.4 gallons of fuel burned being the time to change oil for that combination. The sump capacity factor is interesting and seems to make some sense. Weighting the result based on in^3/hp doesn't make any sense. A high performance car with 1.1 hp/in^3 loafing down the highway at 10% power at 70 mph and 1500 rpm is going to be a lot easier on oil than a .7 hp/in^3 1400cc S'Box getting it's neck wrung at 3,500 rpm to keep up with the same freeway traffic. More important than the extra complication of the method you posted method is that it hides the fact that it's just another variation on the old change oil a X Gallons of fuel consumed,
 
If I gave you my engine type would you guys/gals be able to tell me if my engine can take an extra quart like the above engines? I believe Diesel engines take around 13 quarts of oil - at least the ones I helped on - they always ran those a long time before changing oil. So talking about the above math whiz - Driving 70mph on the freeway @ 2,600 RPM is easier on the oil than going 85mph @ 3,200 RPM even if it cuts your trip time down? [Razz]
 
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87
Location
St. Peters, Mo.
When I was involved in Solo Competition (autocross)and Showroom Stock sports car racing, it was routine to run an extra quart in everything. I never knew of someone having problems due to this, but I did see several instances where someone lost a bottom end to oil starvation when they ignored this recommendation.
 
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260
Location
Newtown, PA
quote:
Originally posted by LARKBILL: When I was involved in Solo Competition (autocross)and Showroom Stock sports car racing, it was routine to run an extra quart in everything. I never knew of someone having problems due to this, but I did see several instances where someone lost a bottom end to oil starvation when they ignored this recommendation.
Well I drive like that everyday and I haven't lost my engine yet. I suppose I'll put an extra half a quart and see if things get frothy.
 
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39,805
Location
Pottstown, PA
I think Too Slick's formula adds the complication of the mpg factor just so that it pukes out a mileage number for the suggested OCI. You're right, though, it's essentially a fuel tabulation. I don't know how power density alters it ..but it is a variable that's specific to that engine. I also would like to see how the "C" factor was constructed ..although using it appears to fall in line with observations ..so someone did some decent cipherin' to pull it from somewhere [I dont know]
 
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