Re: V8 Oil capacity

From: Jeff Lee (jlee@atlanta.nsc.com)
Date: Tue Jun 09 1998 - 15:58:56 EDT


Jon Steiger wrote:
>
> When I change my oil, I like the level to be in the middle; between
> the full and "add" marks. With my '96 5.2l, 5 quarts puts it exactly
> there. (I always change my filter; if you don't change the filter,
> you'll need less, of course.) Its nice not having to worry about
> getting half a quart in there; I just empty, put on a new filter,
> and dump 5 quarts in the top. I run it for a minute or so and shut it
> off, then wait a few minutes and check the level, just to be sure. So
> far, its always been in the same place; right in the middle.

Hmmm... I always thought you were supposed to fill to the full line...

>
> That's how I've always changed my oil. I don't know how important
> the oil level is on the Daks, but with my previous car's engine,
> (Mitsubishi 3.0l twin turbocharged) you had to be careful not to
> overfill it, or you risk "foaming". I forget exactly what causes
> it, but if you overfill the oil in an engine, it can be churned up
> into foam (by the valvetrain, maybe?) and is generally not a good
> thing for your engine. So, I keep mine right in the middle, which I
> figure is the safest point between the two extremes of foaming and
> running out of oil.
>

If the crankcase is too full with oil, the crank/connecting rods will
splash into the oil on every rotation and mix air bubbles into the oil
(foam). This is bad because air is compressible, and when picked up by
the oil pump, having air in the oil can cause reduced oil
pressure/reduced lubrication. Oils have anti-foaming additives to help
prevent bad things like this. I've also heard that having the crankcase
too full can cause excessive oil consumption and can blow out or cause
the main seals to leak, but have never seen this happen.

Most engine designs with which I am familiar (small block Chevys and
Fords, VW's ;) hasn't everyone owned a bug?) have some margin on oil
capacity to avoid such overfilling. In other words, critical oil level
is usually well above the full mark on the dipstick.

I've owned two Honda Accords. Honda called for 3.7qts with filter and
they we're right on the money - if you put in 3.8qts, the oil would be
above the full mark. And of course every dealer I ever let change my oil
always overfilled it by adding 4qts - and my wife asks me why I change
my own oil... I tell her its the only way to have a truly personal
relationship with your vehicle... and make sure its done correctly ;).

Now, so far on 2 out of 2 CC vehicles I have owned, the oil fill spec is
consistently 1/2 qt lower than full... go figure.

jeff
98 rc v8 3.55sg flares fipk



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