It is the weight of the multi-vicosity oil. The 10 is the weight of the oil when cold. The W stands for Winter. The 40 is the weight of the oil when it gets hot.
900ml of4T oil 10w40
not recommended
There should be no problem with mixing them.
SAE 10w40
10w40 Motorcycle oil
The majority of 4 cylinders use a good 10W 40 Motor oil. No It Will Do Just Fine With 10W40
You can only use 10w40 if it is listed in your owners manual as an acceptable weight of oil for the engine.
Sae 10w40.
10w40
10W40 is a thinner oil, and would allow the engine to run more freely, and although both are suitable for winter usage, a thinner oil will usually help the engine start more easily in cold weather.
10w40 in summer and 10w30 in winter. Any heavier oil will cause lifter noise. I have also found the engine on 10w40 will only tolotare about 1/2 quart of lucas oil.
10W40 or 15W40 semi-synthethic