Is it better to fill the engine oil to the dipstick MAX line, or is the MIN line just as good? MKS
Anywhere between MAX and MIN makes no significant difference to the efficiency of lubrication or the car’s performance. But oil levels either above the MAX or below the MIN create risk and can lead to problems.
Outside those limits, the consequences are proportionate to the degree of error, so these lines are guides – not absolute limits. Inside those lines, the variation in the quantity of oil is probably less than 10 percent (well within the engine’s design tolerance of volume, pressure and operating temperature).
When the oil is changed at service, it is good practice to refill exactly to the MAX line (which is a bit more than the essential amount) so there is a safety margin in the event some oil is lost in use through leakage or combustion.
The precise marker line gives a better chance that any change will be spotted, and the level can be topped up before there are any consequences.
Initial filling or top-up to a precise line (top or bottom) also allows a surer check on whether and how quickly the level is changing. The dipstick measures the level of the “pond” of oil in the sump, so the level will read slightly higher when the vehicle has been idle for a while, compared with when it is measured immediately after turning off the engine and some of the oil has not yet drained back into the sump.
For performance experts (purists), gambling with the MIN line does have fractional merit, and over-filling is an anathema…because the webs of the crankshaft splash through the oil in the sump if it is over-filled, and that absorbs fractional energy.
