fredx
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Does anyone remember what year manufacturers changed their recommendation from 40:1 to 50:1.
From 40:1 to 50:1 ?
- Thread starter fredx
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Motorka
Pinnacle OPE Member
There was no single industry-wide changeover year. The shift from 40:1 to 50:1 premix ratios occurred gradually from the late 1970s through the 1990s, depending on manufacturer, engine design, lubrication technology, and emissions regulation.
Key inflection points:
In the 1960s and early 1970s, many two-stroke manufacturers specified 16:1, 24:1, or 32:1 due to lower-quality base oils and less precise carburetion. By the mid-to-late 1970s, improved mineral and early synthetic two-stroke oils allowed leaner oil ratios. Several manufacturers began moving toward 40:1 during this period.
The broader shift toward 50:1 accelerated in the 1980s as:
By the 1990s, 50:1 became common for consumer equipment (chainsaws, trimmers, small outboards) when using modern TC-W3 or JASO-rated oils. Companies such as Stihl and Husqvarna Group standardized around 50:1 for most homeowner equipment using branded oil.
However, this was not retroactive. Engines originally designed for 32:1 or 40:1 often still require those ratios unless explicitly approved for 50:1 with modern oils.
Conclusion: There was no specific year. The transition primarily occurred during the 1980s, becoming widespread by the early to mid-1990s. If you provide a specific engine brand and model, the timeline can be narrowed more precisely.
Key inflection points:
In the 1960s and early 1970s, many two-stroke manufacturers specified 16:1, 24:1, or 32:1 due to lower-quality base oils and less precise carburetion. By the mid-to-late 1970s, improved mineral and early synthetic two-stroke oils allowed leaner oil ratios. Several manufacturers began moving toward 40:1 during this period.
The broader shift toward 50:1 accelerated in the 1980s as:
- Two-stroke oil formulations improved (higher film strength, ashless additives).
- Needle bearings and tighter machining tolerances reduced lubrication demand.
- Emissions standards in the U.S. (EPA small engine regulations beginning in the 1990s) and Europe incentivized lower oil content to reduce hydrocarbon and particulate emissions.
- Manufacturers such as Yamaha Motor Company and Suzuki Motor Corporation had already been specifying 50:1 for many motorcycle and outboard models by the 1980s when used with their approved oils.
By the 1990s, 50:1 became common for consumer equipment (chainsaws, trimmers, small outboards) when using modern TC-W3 or JASO-rated oils. Companies such as Stihl and Husqvarna Group standardized around 50:1 for most homeowner equipment using branded oil.
However, this was not retroactive. Engines originally designed for 32:1 or 40:1 often still require those ratios unless explicitly approved for 50:1 with modern oils.
Conclusion: There was no specific year. The transition primarily occurred during the 1980s, becoming widespread by the early to mid-1990s. If you provide a specific engine brand and model, the timeline can be narrowed more precisely.
