Once you really start looking for direct a answer from a book standpoint among the 8.1's, 'This ones seems all over the place between 6 - 10 quarts and it sort of seems it's depended on what type of oil pan material is used which may have something to do with the years involved but I'm not 100% sure of that as I don't recall any changes to the oil pan per se but many other parts, yes there kind of was.... That mentioned there are two part numbers out from Mercruiser... New # 881653001 (PAN, Oil) Old # 881653.
Volvo Penta says 7 quarts looking at the recommended oil amount to purchase but manuals do have some other numbers mentioned too like in the following thread if interested to read,
https://forums.iboats.com/forum/engi...oblem-8-1-gi-h ....,
https://www.volvopentashop.com/epc/e...%2F7747720_000
Mercruiser says 9 quarts,
https://www.mercruiserparts.com/merc...e-oil-capacity ...,
http://boatinfo.no/lib/mercruiser/ma...ser30.html#/28
The 8.1 engine specs from GM (in a truck),
http://www.duramaxhub.com/gas/gm-8.1-vortec-l18.html
Oil Capacity:
| 6.5 US quarts w/ oil filter
|
But the following info on page 68 is what crusader said for/in 2010 which "should" be the same as 2003,
http://www.crusaderengines.com/classic/#owners
Though checking the dipstick as you go is the most important thing to do until you get used to what the sticks readings are as you slowly fill...The 2 low and high marks near the end of the stick is usually 1 quart even.
1 -
Capacities are dependent on installation angle...ALWAYS use the dipstick to determine the exact quantity of oil required...Add the correct amount of oil to fill to the “FULL” mark on the oil level dipstick...If you are unsure of the correct amount of oil to use during a service interval, perform the following procedure:
1. Drain the oil and change the oil filter.
2. Add four (4) quarts of new oil. ( I ((FT)) say 6 quarts for the 8.1's)
3. Start and run the engine allowing sufficient time for the new oil to circulate and fill the new oil filter.
4. Shut the engine off. Allow a sufficient amount of time for the oil to drain back to the pan...Check the oil level with the dipstick and add the correct amount of oil to fill to the “FULL” mark on the oil level dipstick.
Refer to the Checking Fluid Levels instructions page 41 and Changing Oils instructions page 60 of this manual for complete instructions, important notes and Cautions for checking/changing engine oil.
2 - Check the transmission fluid level at operating temperature and immediately after shutdown of the engine.
