A post I made in 2011 talked about how to select an oil to use in your snow blower. Things have changed recently in the minimum API specification of automotive oils that have outdated those suggestions.
The new API SN specifications have lowered the amount of ZDDP anti-wear additives so much that I’ve decided to no longer suggest regular vehicle oil to be used in air cooled lawn and garden equipment. Air cooled equipment is abused and works so much harder in a much more difficult environment than your daily driver liquid cooled vehicle.
The cost of a quality oil – which is just a few dollars more – versus the possible repair bill is something you’ll have to choose. I made my choice based on my recent experience with an over rev’ing situation which needed the extra protection of an oil designed for air cooled outdoor power equipment.
Recently we’ve finally had enough snow to justify using the snow thrower. On a particularly cold morning I dug out the machine from a snow bank and fired it up. With the choke closed and a rich fuel mixture coming from the carb it seemed to be running at a pretty high speed – but it had been a whole summer. After letting the machine run for a minute or two when I opened the choke the engine raced into over revs – pretty much redlining right away on a cold engine. A quick google search showed Tecumseh engines seem to be well known for spitting rods in these conditions.
The Formula 4-Stroke 10W-30/SAE 30 Small Engine Oil (ASE) oil I had installed in the sump let the engine scream until I realized what was going on and closed the choke again bringing the engine revolutions back down to a normal level. I was stumped as to what the problem might be. Reset the adjustable fuel screw on the carb – fully closed, then 2 whole turns out is the default setting – and let the snow blower heat up with the choke on until it stalled.
Started the engine up again and it was back to the normal puttering sound with the choke on. I figure the governor arm had frozen wide open and was causing the engine to race. Put a full tank of fuel through in 3 hours of snow blowing that day without any more problems. I was glad to have had a quality oil in the sump – just in case things like this happen.
If you need a lower pour point for cold start ups use AMSOIL Formula 4-Stroke® 0W-40 Synthetic Motor Oil (AFF) which is an all climate/all season oil that replaces 0W-30, 0W-40, 5W-30, 10W-30 and 10W-40 oils for ATVs, UTVs, snowmobiles and other power sports equipment with a pour point of -51°C.