Stihl BG 86 Fuel Mix Ratio (50:1 Spec Chart)

The STIHL BG 86 uses a 50:1 gasoline-to-two-stroke-oil mix: add 20 mL of oil to each 1 L of gasoline, or about 2.6 US fl oz per US gallon. Use fresh gasoline with at least 89 AKI, and follow the manual’s ethanol limit. Never run the blower on straight gasoline.

A flashing charger code or a carburetor that will not start can make any yard-tool season frustrating. With the BG 86, fuel preparation is one simple but important check: this is a two-stroke engine, so gasoline alone does not provide the lubrication it needs. I use the ratio chart below to measure each batch rather than guessing from the bottle or fuel tank.

The figures here are a practical reference, not a replacement for the manual supplied with your exact blower. Check its fuel label and instructions, especially if your model or market differs.

STIHL BG 86 fuel mix ratio and chart

The fuel mix ratio is the volume relationship between gasoline and two-stroke oil. For the BG 86, use 50 parts gasoline to 1 part suitable oil. That equals 20 mL of oil per liter of gasoline, or approximately 2.6 US fluid ounces per US gallon.

Measurements are rounded for easy use. The ratio is based on gasoline volume, not the fuel tank’s capacity. The BG 86 tank holds about 0.44 L (14.9 US fl oz), but you should not use that figure to estimate oil for a larger container.

How to measure the oil

Use a marked measuring cup or a fuel container with clear, accurate graduations. Measure gasoline and oil separately, then combine them in an approved fuel container and mix thoroughly. Label the container with the mix ratio and date so no one mistakes it for straight gasoline.

Do not infer the correct ratio from a bottle’s brand name or from an oil cap. Use oil intended for air-cooled two-stroke engines and follow its instructions as well as the blower manual. STIHL two-stroke oil is suitable; an equivalent oil should be approved for air-cooled two-stroke use.

Gasoline and ethanol

Use fresh gasoline with a minimum rating of 89 AKI in markets that use the Anti-Knock Index. AKI is the octane rating shown on many North American fuel pumps. Follow the manual for your market and model; STIHL generally specifies gasoline containing no more than 10% ethanol.

Ethanol can attract moisture, and stored fuel can degrade. If you are unsure how old a mix is or what is in it, do not try to fix it by adding oil. Set it aside for disposal under local rules and prepare fresh 50:1 fuel.

Equipment Setup and Safety Preparation

Safe fueling means preparing the right mix, working with a cool engine, and keeping ignition sources away. Before you open the fuel cap, place the blower on a stable surface outdoors. Check the manual and machine label for model-specific details, and keep the measured premix in a suitable, clearly marked container.

Mix and refuel safely

1. Make sure the engine is off and cool. Do not fuel a hot blower.
2. Choose a well-ventilated outdoor area away from flames, sparks, and smoking.
3. Inspect the fuel container and cap for damage. Measure the gasoline and oil accurately.
4. Close and mix the container as directed by its maker. Avoid spilling fuel.
5. Open the blower’s fuel cap carefully and add the premix without overfilling. Secure the cap.
6. Wipe up any spill and move away from the fueling spot before starting the engine.

Wear eye and hearing protection, sturdy footwear, and suitable work clothing when operating the blower. Before starting, check that the controls work, the tube and nozzle are secure, and the air intake and visible fuel lines look intact. Do not operate the blower if a fuel leak is visible.

A practical batch example

Suppose you want to prepare 2 L of premix for a weekend cleanup. Measure 40 mL of suitable two-stroke oil, combine it with 2 L of fresh gasoline in an approved container, and mix well. That is a measured example, not a special service case; making a smaller batch may be wiser if the blower will sit for a long time.

Field Blowing and Landscaping Operation

Correct fuel is only one part of safe use. Start the BG 86 according to the cold- or warm-start steps in its manual, then keep a firm grip and stable footing. Use the airflow to move debris at a shallow angle, rather than aiming down hard and lifting dust or loose material.

Before starting, move people and pets away from the work area. Watch for gravel, glass, and other objects the air stream could throw. Never aim the nozzle at people or animals, or blow debris toward roads, open doors, or windows. Do not use the blower to move hazardous dust or debris where it could expose others.

Prolonged work in dusty conditions can raise the amount of dust in the air. Take breaks as needed, and stop if you cannot maintain safe footing or control. When finished, shut down the engine and allow it to cool before touching hot parts or preparing it for storage.

Maintenance, Inspection, and Engine Tuning

Routine checks help catch fuel-related problems before they become expensive repairs. With the engine off and cool, inspect the fuel cap, visible fuel lines, air intake, and tube. Clean the intake screen and exterior as the manual directs, and use only the service steps approved for your machine.

If the blower will not start or run well

A starting or running problem does not prove the mix is wrong, but checking fuel is a sensible first step. Ask:

• Is the fuel fresh, clearly identified, and mixed at 50:1?
• Was suitable oil used, and is the gasoline within the manual’s octane and ethanol limits?
• Is there a visible leak or damage around the cap or fuel lines?
• Is the intake screen blocked or dirty?

If the mix is uncertain, stop using it. Drain it only as described in the manual and dispose of it according to local rules. Refill with correctly measured fresh premix; do not add oil to an unknown mixture in an attempt to correct it. If the blower still runs poorly, consult the manual or a qualified service dealer rather than changing carburetor settings without the proper procedure.

Why the ratio matters

Two-stroke oil lubricates moving engine parts as the fuel mixture passes through the engine. Straight gasoline, too little oil, or degraded premix can leave the engine without adequate lubrication and may cause piston or cylinder damage, including seizure. Extra oil is not a safe cure for a guessed or incorrect mix; measure the ratio correctly instead.

Storage and Seasonal Fuel Care

Fuel handling matters at the end of the season as much as it does at the first start. Gasoline blends can age in storage, and the right storage method depends on the fuel, conditions, and manual. Follow the BG 86 manual’s instructions for the tank and fuel system rather than assuming old premix is still fit to use.

Prepare only the amount of mix you expect to use, and mark the container with its contents and preparation date. Store fuel only in an approved, sealed container, away from heat, flames, and living spaces, and follow local rules. If fuel has been sitting and you cannot verify its age or composition, do not pour it into the blower.

Before putting the machine away, stop the engine and let it cool. Clean the exterior and intake screen as directed, check for damage or leaks, and keep the blower in a dry, secure place. For longer storage, use the fuel-system steps specified in the model’s manual.

Conclusion: Check the mix before the season starts

The BG 86’s standard mix is 50:1: measure 20 mL of suitable two-stroke oil for each liter of gasoline, or about 2.6 US fl oz per US gallon. Use fresh fuel, follow the manual’s gasoline and ethanol requirements, and never run the blower on straight gasoline. A labeled container and measured batch make seasonal refueling more reliable.

FAQ

What is the fuel mix ratio for a STIHL BG 86?
The BG 86 uses a 50:1 gasoline-to-two-stroke-oil mix. That means 20 mL of oil per 1 L of gasoline.

How much oil goes in one US gallon of gasoline?
Use about 2.6 US fl oz of two-stroke oil per US gallon of gasoline for a 50:1 mix.

How much oil do I need for 5 L of gasoline?
Measure 100 mL of suitable two-stroke oil for 5 L of gasoline.

Can I use straight gasoline in the BG 86?
No. The BG 86 is a two-stroke engine that requires premixed gasoline and oil. Straight gasoline can cause inadequate lubrication and serious engine damage.

Can I use any two-stroke oil?
Use STIHL oil or an equivalent oil approved for air-cooled two-stroke engines. Follow the oil label and the BG 86 manual; do not change the mix ratio based on the oil’s brand.

What octane gasoline does the BG 86 need?
In markets using AKI, the specified minimum is 89 AKI. Check your model’s manual for the exact fuel requirements in your market.

How much ethanol can the gasoline contain?
Follow the manual for your model. STIHL generally specifies no more than 10% ethanol.

Can I add oil to old or unknown fuel to correct the ratio?
No. If you cannot confirm the fuel’s age or mix, do not try to correct it by adding oil. Drain and dispose of it according to local rules, then make fresh 50:1 premix.

Does the fuel tank’s capacity change the mix ratio?
No. The tank holds about 0.44 L, but the ratio stays 50:1. Measure oil according to the amount of gasoline you are mixing.

What should I do if the blower still runs poorly with fresh fuel?
Stop and check the manual’s inspection steps, including the intake and visible fuel lines. If the problem remains, ask a qualified service dealer to diagnose it rather than adjusting the carburetor without the correct procedure.

(This article was written by one of our staff writers, Harrison Croft. Visit our Meet the Team page.)