451 Oil Change

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The Drain Plug

If you look under the car you will clearly see the oil filter, it is a large black cylinder.

To the right of that is the drain plug (circled in red below).

Draining The Oil – Original Drain Plug

Drive the car until it is up to normal operating temperature, about 80 degrees.

Unscrew the oil filler cap (circled in green below) and remove the dipstick (circled blue).

Remove the drain plug (24mm) and reposition the bowl so it actually catches the oil. The drain plug is about 3″ long and has a mesh filter built into it. Remove the copper washer and ensure that the mesh filter isn’t clogged up.It’s worth mentioning that every time you remove and refit the sump plug, you risk splitting the sump.

Draining The Oil – Sucky Sucky

Removing this will allow the oil to flow from the engine. However, I still recommend pumping the oil out of the dip stick tube like in the previous models. It may sound counterintuitive but here is the reasoning.

Using a pump is far cleaner. It may not be as fast or get every last drop out but it can save you later problems.

I opted for the Pela 6000 oe Sealey TP696 which, for about £40, is well worth the outlay.

The sump is aluminium (alooomi-num) which, although it’s a soft metal, has shown a tendency to crack.

It could be internal faults with the cast aluminium but there have been more and more reports over the years of these sumps cracking when the sump plug was removed or replaced. Fitting a new sump is a very hard job.

Also, the sump plug isn’t aluminium so you can get bi-metal corrosion between the threads.
The soft aluminium threads easily strip leaving you with no choice but to fit a new sump.

Draining The Oil – Check Valve Drain Plug

To save the hassle of broken sumps and stripped threads, I decided to fit a check valve drain plug.
Once one of these is fitted, you never have to remove it again. Ideal. I bought mine here. (my own store).

However, if you don’t want to support me, here are affiliate links so I make 10p on your purchase.

eBay US – Stahlbus Valve
eBay UK – Stahlbus Valve

You want the M22x1.5x12mm version.

Once this is fitted, to remove the oil you just have to unscrew a cap, push in a supplied fitting and the oil comes flowing neatly out of the attached hose. Stahlbus recommend using the factory torque spec for the original sump plug. In this case, smart recommend 65Nm which sounds a little high to me but hey! What do I know?

Replacement check valve drain plug                                        Drain valve protective cap                                      Drain hose bayonet fitting

Once it’s fitted, you never have to remove it ever again.

The drain hose bayonet fitting comes with a section of translucent hose.

The fitting just pushes in and twists to lock into position.

A little video to show you how it works.

Make an oil catching container.

If you can, jack the opposite side of the car up slightly.

Unscrew the protective cap…

…to reveal the check valve sump plug. The oil on the threads is from the previous oil change.

Throw your hose into the container and connect up the drain hose to drain the oil.

Remove the oil cap to allow air to flow in as the oil flows out.

Eventually, the oil will stop flowing.

Disconnect the drain tool and refit the protective cap.

What About The Drain Plug Filter?

I just leave it out. It’s more of a fine mesh. I have never seen anything trapped in this mesh during a service. Anything floating in the oil will get trapped in the actual oil filter and removed during the service.

What About Leaving The Mesh In Place?

Definitely don’t do that. It might clog up with shit and you’d not know unless you remove the drain plug (which we are obviously trying to avoid).

Removing The Oil Filter

The filter simply unscrews in an anticlockwise direction. In the unlikely event that the filter is seized onto the thread, you may have to utilise a strap wrench like a ‘Boa’. Make sure that you have the oil catcher in place when you remove the filter as you will get a small stream of oil. The oil filter will be totally full too.

The oil filter housing will continue to drip for a while.

Refitting The Oil Filter

To save the engine having to circulate a lot of air before the oil flows properly, It’s a good idea to fill the filter.

Wipe some fresh oil onto the rubber seal and screw onto the engine in a clockwise direction.

Smart recommend torquing the oil filter up to 14Nm if you have the equipment. If you don’t (as most people won’t), hand tight will be fine. Don’t go mad on it though.

I do recommend getting the proper smart filter though. The one I had left was a little long.

Filter smart part number A 132 180 00 10 or Mitsubishi number 1230A040.

Refitting The Sump Plug

Take a new copper washer and place it over the sump plug. Screw the sump plug into place and torque to 65Nm. This seems very high high to me but smart should know best. Personally I finger tight the plug and then add 1/8th of a turn. What you do is up to you.

Washer smart part number A 0189974445. (buy it from a smart dealer). Or just search online for a 22mm copper washer that looks the same.

If you want to reuse the washer, heat it with a flame until it glows cherry red then throw it in cold water. This anneals the copper making it soft again so it can deform and make a seal. I wouldn’t do this too often though. Eventually it’ll deform too much.

Refilling The Oil

Using the correct fully synthetic oil (5W-30 is suitable for the UK climate) put in 3 litres of oil into the oil filler hole in the top of the engine (circled in green below).

The smart fortwo 451 takes approximately 3.4 litres of oil to reach the maximim level but remember that you cannot physically remove all of the oil. I like to put 1 litre in at a time. Do 3 of those and then 400ml.

Allow the oil to settle for a few minutes, check the level with the dip stick. Add more oil a bit at a time and keep checking until the oil level is about halfway between the minimum and maximum marks.

Replace the oil filler cap and the dip stick. Ensure the filler cap is securely tightened down.

Check And Double Check

The oil level is very important so run the engine for about a minute, this allows the oil to circulate around the system. Any air in the system or the new filter will be pushed into the sump.

Turn the car off and wait a few minutes before checking the oil level on the dipstick again. The displacement of air can cause the oil level to fall so top up as necessary.

Once it’s at the halfway point again, take the car for a drive to get it up to operating temperature.
Once it is, check the oil level 3 times to ensure it’s not too high or too low.

Ideally you should check the oil level every week.

Oil Capacity

Engine oil capacities are all listed here.

451 Diesel Oil Change

The CDI engine is the different to the petrol model so see here for the diesel oil change.