Checking the Oil Level
The oil in your car keeps things moving and not melting into one big part.
The dipstick shows you the level of the oil in the engine, it has a bright red top and
is found on the right side of the engine bay. (circled in green in the picture below).
The filler cap located directly next to the dipstick is where fresh oil is added. (circled in red below).
When you check your oil level the car must be at full operating temperature (3 blobs)
The engine must be switched off. The car must be parked on a flat level bit of ground.
Always use fully synthetic oil as originally recommended by smart like Mobil1 or similar fully synthetic oil. Don't blindly use 0W-40, read here about oil specs.
If you over fill a smart with oil, don't start the engine until you have sorted it out.
The amount of oil needed to go from the bottom notch of the dipstick to the top is
0.7 litres so as long as you put in about half a litre at a time you will never overfill.
Always allow the car to sit for at least 10 minutes after adding oil to allow it to level out for
a true reading on the dipstick. When you are happy with the oil level make sure the oil filler
cap is put back on straight and firmly closed. Check the oil level every week without fail.
If you overfill it, suck the excess out of the dipstick tube with a hand oil pump available from boat shops, you could do it with a length of thin hose and your mouth but you know what will happen.
One trick with the hand pump is to place the pipe against the dipstick and mark
the distance from just below max to the top of the dipstick. That way the pump will
stop sucking oil as soon as the oil level goes below max.
This information can be seen in greater detail on the oil changing guide found here.
If you find yourself topping up regularly there could be something wrong like a damaged turbo
seal, cracked engine block, damaged head gasket, warped head, faulty top breather pipe etc.
What's Wrong With Overfilling?
The oil level is set so there is no way that oil can be blown through the lower breather pipe in
the TIK pipe. This would shower the turbo compressor wheel with oil which could damage it.
This oil would then be blown into the intercooler making it less efficient.
The remaining oil would then get blown passed the throttle body and into the engine.
Any extra fluid getting into the cylinders is bad and will increase compression which can
damage the piston rings causing a loss of compression and a lack of power.
The resulting emissions will very quickly clog the catalytic convertor causing it to fail.
The lambda sensor will bring up an engine check light on the dash.
The damaged catalytic convertor can then fail the MOT.
So, let's recap. If you overfill the car with oil you might have to replace the turbo,
recondition the engine, replace the exhaust and pay for a new MOT.
In addition to that, if you fill it too much, the crankshaft won't splash lubricate the bores correctly
and the oil can become aerated which reduces its ability to lubricate moving parts.
This causes excessive friction, things get hot and then seize up.