What's better: more oil or less oil?

[JonathanC]

The computer in my car was indicating the other day that the oil level was just above the minimum. I decided to buy some oil and filled it up myself and it's now just below the maximum. However, I'm wondering now whether this was the best thing to do.
Any ideas?

[Steve_D]

If you are in the band between max and min no problem.
Don't worry about it.

Steve

[davepoth]

Chances are that closer to minimum than maximum is better since there's less oil thrashing around in the sump; minimum is completely safe for the engine though. However doing that means that you'll have the bonnet up more often to put a little bit of oil in, which is annoying.

[Sam_68]

davepoth said:

Chances are that closer to minimum than maximum is better since there's less oil thrashing around in the sump; minimum is completely safe for the engine though.

On the other hand, the less oil you have the hotter it will get if cooling is marginal and (more importantly) the more chance you have of sump surge. There's also more of a margin of safety if you develop a slight leak (for example from a cracked sump).

If the engine and installation have been designed, tested and developed adequately, the engineers will have allowed a sufficient margin of safety at either end of the scale (oil to top and bottom mark), but even major companies don't always get it right, even today.

The oil pressure warning light quite frequently came on with my Skoda Octavia vRS company car when driving 'briskly' around roundabouts, when the oil level was anywhere close to minimum (in fact I used it as a reminder to top the oil up). This probably didn't do the bearings a whole lot of good, though to be fair, they lasted the 100K miles until I handed it back to the lease company. I've also had the cracked sump scenario (on my Westfield).

I've never (personally) had an oil pressure warning light come on due to aeration on an engine that has been kept topped up to the upper mark, so personally I'm inclined to keep it at the upper level on my own cars.

[Classic Grad 98]

The race car gets minimum to reduce crank windage, road car gets topped up.

[AGANON]

JonathanC said:

The computer in my car was indicating the other day that the oil level was just above the minimum. I decided to buy some oil and filled it up myself and it's now just below the maximum. However, I'm wondering now whether this was the best thing to do.
Any ideas?

Its always best to have the oil indicating the maximum mark on the dipstick , if you do go over the mark it could cause serious problems for the engine , i always fill the oil level to just under the max mark to be sure , its a long and aggrivating process extracting oil from an engine but thats just me i would say its better to always aim for the dipstick max mark remember the amount between the min and max mark is a litre so even though yout car may take 4.7-6.7 litres of oil its always gunna be a litre on the dipstick

AGANON

[RedOctober]

With the oil level at minimum, you've also got less volume of oil to absorb engine contaminants between services, so the oil will be dirtier when you change it. Since the manufacturer allows you to run an oil level between minimum & maximum, then keeping the oil level at maximum will prevent possible oil starvation during hard cornering. Depending on the rate at which the engine uses oil, if you run the oil level at minimum then you've got no 'safety margin' if the oil level falls further due to small leaks & oil being burnt by the engine. Keeping the oil level at maximum gives the greatest volume of oil to absorb contaminants & lessens the chances of the oil becoming saturated with contaminants between services...