My lawn mower manual asks for SF grade 10 W 30 oil. The Oil I bought does not say SF class and the person in the Autozone does not k now what SF means. Please explain what really SF means and is it sold anywhere?
You don’t say what this mower is but most people just buy 10w30 Lawnmower Oil . That is what it says on the bottle . That is what I have done for years and the engine usually outlasts the mower frame.
SF is an obsolete API oil classification grade from the 1980’s, the current grade is SN, use the current grade.
Newer is better, if that isn’t clear. SG replaced SF, SH replaced SG and so on to SN.
You will find it in hardware stores like Home Depot or Lowes and maybe in the garden section of Walmart. It costs more and usually sold in 20 oz bottles instead of quart bottles. You pay more to get less. Make sure you get 4 cycle oil and not 2 cycle oil. It is also sold under brand names like Briggs & Stratton.
Why would you buy it? It has two chemicals not found in today’s oil, Molybdenum Disulfide aka Moly-B and a zinc/phosphorus compound known as ZDDP. These increase the lubricity of oil but have been removed for modern vehicle engines because they degrade catalytic converters.
If it’s a Briggs, they now say you can use 10-30 Synthetic year round in everything. I use Mobil 1 in lawn mowers, snow blowers, generator, etc. all the time. I think you have an old manual or it’s one of those Liquid Crystal engines.