Generally 4 Cycle 5-6 HP vertically shaft Briggs holds more oil than I expect. Time has gotten away since my 70s-90s regular repairs/troubleshooting. It got my attention today when I was given a 5 HP Weed Eater 5000 Series Push Mower (very low end). Model # 961140003, Serial # 961140003 14, 2006 -2008 in one spec, 1 qt of oil Cap?, 6 oz low today. At least 6 oz put the oil back on the stick. If it actually holds 1 qt 6 oz low is not that critical IMO.

The mower’s Vitals (Fire/Fuel/Compression) except low oil were not bad and it ran good. I doubt the mower had any real time on it since I have noticed it sitting outside about 5 yrs w/o any use.

I tried to find a general Briggs chart on oil capacities (attached) even though I measure my personal oil from full before changing on my Briggs 6.5 Etc. (another donor that runs like a top that was said to be locked).
The chart is from this link since it has copied into a different format w/o Briggs Pictures and names. Please share a chart to compare info.

http://www.briggsandstratton.com/support/frequently-asked-questions/How%20much%20oil%20is%20required%20for%20my%20engine/~/media/28E7DD88EFD641C39D9A2DD89C70D17C.ashx

Vertical Shaft Engines
Always monitor oil level when adding.
(See Owner’s Manual for proper procedure.)
Model Name &
Horsepower Picture Approximate Oil
Capacity
3.5-3.75 HP
20 fl oz
(.59 l)
4.0-4.75 HP
20 fl oz.
(.59 l)
5 HP
22 fl oz.
(.65 l)
5-6 HP
20 fl oz.
(.59 l)
Vertical Shaft Engines
Always monitor oil level when adding.
(See Owner’s Manual for proper procedure.)
Model Name &
Horsepower Picture Approximate Oil
Capacity
5-6.5 HP
20 fl oz.
(.59 l)
6-6.75 HP
22 fl oz.
(.65 l) *
6-6.75 HP
22 fl oz.
(.65 l) *
8-11 HP
36 fl oz.
(1.06 l)
OHV
9-13.5 HP
48 fl oz.
(1.42 l) *
*If engine is equipped with Oil Filter, add approximately 4 oz. (.12L).
(See Owner’s Manual for proper procedure.)
Vertical Shaft Engines
Always monitor oil level when adding.
(See Owner’s Manual for proper procedure.)
Model Name &
Horsepower Picture Approximate Oil
Capacity
12-14 HP
48 fl oz
(1.42 l)
(Single Cylinder)
15-16 HP
48 fl oz.
(1.42 l) *
Equipped
& 13.5-17.5 HP
48 fl oz.
(1.42 l) *
15.5-17.5 HP
48 fl oz.
(1.42 l) *
18-20 HP
48 fl oz.
(1.42 l) *
*If engine is equipped with Oil Filter, add approximately 4 oz. (.12L).
(See Owner’s Manual for proper procedure.)
Vertical Shaft Engines
Always monitor oil level when adding.
(See Owner’s Manual for proper procedure.)
Model Name &
Horsepower Picture Approximate Oil
Capacity
16-23 HP
48 fl oz.
(1.42 l) *
& 22-26 HP
60 fl oz.
(1.77 l)*
*If engine is equipped with Oil Filter, add approximately 4 oz. (.12L).
(See Owner’s Manual for proper procedure.)
Horizontal Shaft Engines
Always monitor oil level when adding.
(See Owner’s Manual for proper procedure.)
Model Name &
Horsepower Picture Oil Capacity
2.4 HP
13.5 fl oz
(.4 l)
4 HP
20 fl oz.
(.59 l)
3.5 Hp
20 fl oz.
(.59 l)
* OHV
5-7 HP
20 fl oz.
(.59 l)
*Intek Snow holds
16 fl oz.
(.47 l)
OHV
5.5-6.5 HP
20 fl oz.
(.59 l)
Horizontal Shaft Engines
Always monitor oil level when adding.
(See Owner’s Manual for proper procedure.)
Model Name &
Horsepower Picture Oil Capacity
6 HP
24 fl oz.
(.71 l)
7.5 HP
20 fl oz.
(.59 l)
7.5 HP
30 fl oz
(.90 l)
8-10 HP
44 fl oz.
(1.3 l)
OHV
8-11 HP
28 fl oz.
(.77 l)
Horizontal Shaft Engines
Always monitor oil level when adding.
(See Owner’s Manual for proper procedure.)
Model Name &
Horsepower Picture Oil Capacity
OHV
8-11 HP
28 fl oz.
(.77 l)
OHV
8-11 HP
28 fl oz.
(.77 l)
9 HP
32 fl oz.
(1.2 l)
9-11 HP
28 fl oz.
(.77 l)
11-13 HP
32 fl oz.
(1.5 l)
11-12 HP
48 fl oz.
(1.42 l)
Horizontal Shaft Engines
Always monitor oil level when adding.
(See Owner’s Manual for proper procedure.)
Model Name &
Horsepower Picture Oil Capacity
16-23 HP
48 fl oz.
(1.42 l)*
18-19 HP
48 fl oz.
(1.42 l)*
*If engine is equipped with Oil Filter, add approximately 4 oz. (.12L).
(See Owner’s Manual for proper procedure.)
.75-1 HP
3.0 fl oz.
(80ml)
24 fl oz.
(.71 l)

Here is a link that might be useful: Briggs oil capacity info