4-Stroke Engine Oil, SAE 30, 500ml

Five hundred millilitres is the single service size. Most small air-cooled four-stroke engines hold less than half a litre in the sump, so this bottle covers one oil change on a mower, a generator or a water pump with nothing left standing around to go dusty in a store.

It is also the sensible bottle to keep with the machine for topping up. A small engine uses a little oil as it works, and the gap between the low mark and the high mark on a mower dipstick is a very small quantity. Buying five litres to add a splash is how oil ends up sitting open on a shelf for two years. SAE 30 is the straight grade that most small four-stroke engines specify, and it is the usual recommendation for mowers and generators in a warm climate. Remember that in a four-stroke the oil goes in the sump and the petrol goes in the tank, separately.