8.1 oil capacity, what's right?

Haulin' 8.1 · July 17, 2005

For my fellow 8.1 owners who check/change thier own oil, how much do you use for fill up. I just read an interesting article in the newest Car Craft magazine (Sep. '05) discussing the ill effects caused by having too much oil in the crankcase on oil pressure and HP, therefore mileage also. When the oil level in the pan is too high the rotating assembly will constantly splash through it dragging down the crankshaft and areating (foaming) the oil. By keeping the oil level "just" high enough engine power was increased by 14HP @ 5800 and oil pressure was rasied from 71 to 82 PSI. This was on a BBC based 572 CID marine engine and oil fill was reduced from 9 qts. to 7.5 in a custom high capacity Moroso pan.

Now I knew this stuff in theory already but it got me to thinking about the truck. You see the owners manual and the Helms manual both are very specific that the 8.1's oil capacity is 6 qts. w/o a filter change and 6.5 qts. with a filter change. But when I do an oil change on the truck. like last Friday afternoon, it takes 7 qts. to reach the top of the operating range level on the dipstick. My stepdad had wrote 7 1/2 qts. on my engine cover the first time I changed the oil and I went by that and actually overfilled it a slight amount but thought about how it slowly leaks oil and didn't worry too much about half a quart. So I left it alone at half a quart over "max". Though I will remove anything more than that on any vehicle I work on to reduce the chance of convertor damage due to excessive oil burning, a common cause of converter failure.

Now after reading the article I'm wondering if I would be better off by striving to maintain a maximum of 6.5 qts. in the engine at all times. This would bring the level to the middle of the operating range on the dipstick and lower my usual level by at least a half a quart but a quart less than it has right now. If this would increase engine life and improve efficiency then what's too loose?

Is it just my dipstick that's ranged a little higher than specs or do you guys find the same amount of oil is required to reach the top of the range? Does anyone find that 6.5 qts. fills thier engine up to the top of the range?

Anyone have any thoughts to add? Please do.

Vernon

BBSilverado · July 17, 2005

I put 6.5 qts in and the stick shows the middle of the safe zone. So, I would say that 7.0qts is OK and that would be on the high end of the safe zone. 7.5 may be too much unless he used a larger capacity oil filter.

moo snutz · July 18, 2005

I just changed my oil for the first time a while back. I put in 6.5 qts & it seems to be right in the sweet spot on the stick. I just finished up a 500 rnd trip up to CO. and back today and averaged 80 mph in 89-94 temp (12.5mpg avg) & on each fillup, the oil was in the exact same spot on the stick - nice & gold

TieRod · July 18, 2005

Mine must be a little off. I always fill to the full mark 6 qt right on the money. Maybe thats why it ran so good or was the nitrous bottle in the truck box I get so confused these days.

c502cid · July 18, 2005

7 qts here each and every time. Just a hair over the top of the top line.

Although I'm a big Car Craft junkie myself, I try not to get too caught up in production motors vs specialized hi-po motors. For instance, in my 502 powered

Vette, I get a little more concerned with oil windage, indexing spark plugs, etc. In production motors I just don't see that much of a difference.

The same Car Craft magazine a few years ago was talking about that you need to add an extra quart of oil to your crankcase if you do anything other than drag racing to be sure the pickup never gets air going around corners.

Keep the oil between the lines and you'll be fine. The motors are designed to work ok a quart above or a quart below the lines.