General Motor Mower Advice
Type Of Petrol
One of the commonest queries to the club is about the correct type of petrol to use with a vintage lawn mower. Although many old motor mowers with four stroke engines were made during the period when leaded petrol was standard the prevailing view is that these machines will run perfectly well on ordinary modern unleaded fuels. Lead based additives were used in petrol to help lubricate valves and prevent preignition on four stroke engines. However, old mower engines do not generally run fast enough, hot enough or at sufficient compression ratios for the presence of an additive to be a major factor. Two stroke engines do not require leaded fuel or additives.
Smaller and faster running engines made after about 1970 may benefit from use of an additive. Local mower repair shops will be able to advise customers on mowers with this type of engine which falls outside the scope of the Old Lawnmower Club.
Many older motor mowers require 18mm spark plugs that are no longer available. Some specialist vintage engine part suppliers may be able to assist.
A useful source that cross-references some old spark plug number with the modern equivalent can be found here.