Model # 51978 Serial # 314000001 - 314999999 Product Name 18in Straight-Shaft Gas Trimmer. A weed trimmer is a useful garden tool, especially if you live somewhere hot and humid where weeds tend to flourish. Weed trimmers run on a mixture of gas and oil, and two-cycle weed trimmers require a proper mix to run well. Too little oil and the engine will overheat and seize up. If there is enough fuel and it is fresh, lightly shake and swirl the weed eater to ensure that oil and gasoline are not separated. If you are using the weed eater for the first time after several months, you should swap the old fuel for a new mixture. Many string trimmers require a 40:1 or 50:1 gas-to-oil ratio.
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Finding the correct gas to oil ratio for a string trimmer is not as easy as it should be. Although the industry is moving slowly toward a consistent 50:1 ratio recommendation, there are still variations between manufacturers.
Recommended gas to oil ratios for the most common string trimmer brands:
It’s important to note that some brands have models that use different ratios than those stated above. It gets ridiculous with some brands that have two or three different recommended ratios depending on the model of your equipment.
As such, it’s always best practice to check the owner’s manual but these represent the bulk of each brand’s offerings.
Stihl doesn’t mix words when it comes to mixing gas and oil. They maintain a consistent 50:1 ratio with all of their 2-stroke equipment (source). I appreciate this level of consistency.
Note that older owner manuals for ECHO products recommended strange, sometimes impossible gas to oil ratios such as 32:1. But in 2019 ECHO revised their recommendations to allow for a 50:1 ratio for all ECHO two-stroke engines using their branded two-cycle oils (source – see page 23).
** Husqvarna’s older manuals used to call for a 40:1 ratio. I contacted Husqvarna for clarification and they verified that newer models all use 50:1 but some older models do in fact require 40:1. I did not receive any specific guidance on the year that this change occurred so I recommend checking your owner’s manual if you have an older model string trimmer just to be sure.
McCulloch equipment uses 40:1 per the Husqvarna website (source).
Virtually every model of Craftsman string trimmer that I looked at used 40:1 gas to oil ratios, though I was unable to find a definitive source that could confirm that this is true of all of their equipment.
Ryobi, though best known these days for their battery-powered tools, does still maintain a few gas model trimmers. They currently recommend a 50:1 ratio for their 2-stroke trimmer engines (source).
Does Gas To Oil Ratio Really Matter?
Two-stroke engines are designed to run on specific gas to oil ratios. Straying from the manufacturer’s recommendations can result in various engine problems and potential damage.
Examples of problems that can be encountered from inaccurate gas to oil ratios include:
- Trouble starting
- A trimmer that starts but then dies when the throttle is engaged
But these are just symptoms. The real issue is the potential damage that can be caused to the engine itself.
A two-stroke engine requires lubrication directly in the fuel since it does not have a separate oil compartment to draw lubrication from. Using an inaccurate gas to oil ratio means you are either not providing enough lubrication, or you are giving it too much.
Either way, the motor will not run as efficiently as it is designed to if you alter fuel ratio from the manufacturer recommendations.
Can I Use 4-Stroke Oil Instead Of 2-Stroke?
You should never use 4-stroke oil in a 2-stroke engine. 4-stroke oil will gum up over time when mixed directly with the gas, causing longterm motor issues and potential damage.
Some people have claimed success with using 4-stroke oil but short-term testing does not allow for adequate evaluation of longterm impact. There is absolutely no reason that you should place your 2-stroke equipment at risk with this unproven theory.
Should I Buy Premixed Fuel Or Just Mix The Gas And Oil Myself?
For ease of use, premium ingredients, and precise gas to oil ratios, commercially-prepared premixed fuel is a better solution than mixing the gas and oil yourself.
I spent years mixing my own fuel, priding myself on money saved in the short term. In the end, I was being penny-wise but pound-foolish. The gas I was using was from the pump at a local station. Pump fuel contains ethanol which can damage small engines.
In my case, it caused the inner lining of the fuel lines to dissolve resulting in a lot of work rebuilding the carburetor and trying to get the darn thing to run again.
I made the transition to premixed fuel and have never looked back. There are several quality products available on the market and I’ve already done a lot of the research by comparing the best premixed fuels so have a look at that before buying.
Oil For Weed Wacker
And yes, premixed fuel does cost more when you look strictly at price but you have to factor in that you are getting ethanol-free gas mixed precisely with 2-stroke oil and extended shelf life that far exceeds a homemade mix.
Toro Weed Wacker Fuel To Oil Ratio
Where Can I Find My String Trimmer Manual Online?
The first place to look for a string trimmer manual online is the manufacturer’s website. Companies generally provide a directory of owner manuals in PDF format available for download.
Here are the direct links to owner manual directories for several leading string trimmer manufacturers:
If your brand is not listed, try a simple Google search. Any reputable manufacturer will have an online directory that is usually searchable. You can search for your specific string trimmer model and view or download the owner’s manual.
This manual will provide a definitive answer on the correct gas to oil ratio for your specific string trimmer model.
Conclusion
String trimmer gas to oil ratios vary by manufacturer but most are moving toward a 50:1 ratio. It is likely that in the years ahead this will become the defacto gas to oil ratio for 2-stroke yard tools.
Toro Weed Wacker Parts
In the mean time, it’s important to make sure that you are abiding by the recommended mix ratio specific to your brand and model. This will ensure that your string trimmer runs as efficiently as possible and receives the proper amount of lubrication, preventing damage and poor performance.