There are three main types of oil:
You must use fully synthetic oil in your smart engine.
How Can I Tell If It Is Fully Synthetic?
It should state this info somewhere on the bottle, if it doesn't tell you in straight English that it is fully synthetic then generally they are hiding something or trying to blind you with science.
Don't buy any engine oil which does not have the ACEA and API rating on the label.
It doesn't really matter. For it to be classed as a fully synthetic oil at a particular weight (0W-40, 10W-30 etc) it has to pass strict tests and be within stated guidelines. People still feel better about using big brand names like Mobil1, Shell Helix and Castrol.
0W-40, 10W-30, What?
These pair of numbers are known as the weight. These tell you the viscosity (thickness) of the oil. The first number is its cold viscosity, as the oil heats up it thins out allowing it to flow better.
The lower the number, the thinner the oil is.
The second number is the viscosity when at 212 Fahrenheit (100°C), 30 oil is thinner than 40 oil.
The W stands for 'winter' which is the thickness of the oil at 0° Fahrenheit (-18°C).
It is measured by the number of seconds it takes for a set amount to be pumped through
a tube of a particular size. This piece of aparatus is called a viscometer.
So What Oil Viscosity Do I Need?
It actually depends on the ambient temperature of where you live.
If you live in a very cold climate like Canada then you should consider 0W or 5W.
For us in England (which is a warm climate no matter what your Nan says) you
will do OK with 10W. For the hot places like Spain, consider 15W or 20W.
Isn't 0W-30 Or 0W-40 The Best Alround?
No, they are really designed for use in cold climates and performance cars (smart cars don't
count no matter what BHP you claim). Lower W numbers give better cold starts that protect the engine quicker as the lower viscosity can splash and flow through the system more efficiently.
Using 0W in a smart engine in anything but a cold climate will cause faster engine wear
on cold starts and won't properly lubricate until it reaches full operational temperature.
450 & Roadster
If you live in the UK and have a smart of any description then use
5W-30, 5W-40, 10W-30 or 10W-40 oil.
I personally recommend 10W-40 for all 450s and Roadsters in the UK.
451 & Forfour Petrol
Mitsubishi make the petrol engines and they seem to recommend 5W-30 no
matter where you are. 5W-30 is fine unless you live in a VERY cold or VERY hot
country in which case go for 0W for cold and 10W for hot.
451 & Forfour Diesel
This is where smart start confusing things. The diesel engines are Mercedes units and
the fortwo diesel has the same engine in both the 450 and 451 variants. However, in
the 450 the recommend 10W-40 for UK temperatures but 5W-30 in the 451.
I have tried both of these in my 451 diesel and it was fine and I do a lot of miles.
For the Forfour, I'd stick with 10W-40 and vary that up or down for cold or hot countries.
Smart Recommended Oils
Smart published a list of acceptable oils for use in smarts to all their garages.
However, this does not mean that every oil below is suitable for your smart.
You should still use an oil designed for the environmental temperatures in your country.
Aral Supertronic G
BP Visco 7000 GM
Castrol DCO Topup
Castrol Formula SLX
Castrol Formula SLX Longtech
Castrol Syntec European Formula
Elf Excellium Full Tech
Gulf Formula Extreme
Total Activia Energy 9000
Mobil 1 Turbo Diesel
Addinol Super Power MV 0537
Agip Formula LL DC
Aviaticon Unique DC
Divinol Syntholight MB
Elf Excellium 229.5
FormulaShell Ultra AB
Fuchs Titan Supersyn SL
Galp Formula XLD
Gulf Avantgarde K
Gulf Formula GX
Igol Process Compact P
INA Futura MB
Labo MB 229.5
Liqui Moly Longtime High Tech
Megol Motorenoel New Generation
Mobil SHC Formula MB
Motorex Profile M-XL
Motul 8100 X-Max
Motul Specific MB 229.5
OMV Full Syn MB
OMV Full Syn Plus
Panolin Exclusive BD
0W-40 is NOT the quickest way to protect your engine from cold start up.
So 'Paul' if you insist on saying I am wrong, at least have the balls to put your email address.
I said nothing about 'Race or track cars', I said performance cars.
Race and track cars require the least internal friction to release the most power from the engine.
These engines are also rebuilt every few thousand miles. The smart engine isn't.
By printing this document I state I have read and understood this disclaimer