The right fuel and oil for STIHL two-stroke engines

In STIHL petrol machines with a 2-MIX or 4-MIX engine, use a fresh mix of petrol and two-stroke oil in the ratio given in the manual for your specific model. As a guide, with STIHL oil (or a good-quality TC-class oil), STIHL often specifies a ratio of 1:50 (1 part oil to 50 parts petrol). Mix the fuel in an approved fuel can, use it up promptly and don’t leave old fuel in the tank during a longer break. The wrong ratio or old fuel can seriously damage the engine.

At Zakservices in Senica, we’ll help you choose the oil or a ready-mixed fuel and show you a safe procedure for your STIHL machine. Below is a practical overview without shortcuts that put the engine at risk.

What you’ll learn in this article

• which mixing ratio is usual for STIHL and why you should always check the manual
• which petrol and which two-stroke oil to use
• how to mix and refuel safely
• how long to store your own mix and when to choose a ready-mixed fuel such as MotoMix
• common mistakes, safety, FAQ and contact details in Senica

Why the right fuel determines the life of the engine

A two-stroke engine (and the STIHL 4-MIX too) is lubricated by the fuel mix. Too little oil risks overheating and a seized piston. Too much oil means smoke, carbon deposits and poorer running. Old fuel containing ethanol absorbs moisture, and the oil separates from the petrol. Even after shaking, such a mix may no longer be fit to use. The right mix is cheaper than repairing the carburettor or cylinder of a STIHL chainsaw, brushcutter or leaf blower.

Mixing ratio: 1:50 as a guide, and always the manual

STIHL’s general recommendation for many machines with 2-MIX and 4-MIX engines is 1:50.

Examples for a 1:50 ratio (as a guide only):

• 1 litre of petrol and 20 ml of two-stroke oil
• 5 litres of petrol and 100 ml of oil

Important: always check the ratio, the type of oil and the approved fuel in the manual for your model. If the manual gives different figures, the manual applies. This article is no substitute for the manufacturer’s manual.

The STIHL 4-MIX isn’t a conventional car-style four-stroke engine with a separate oil sump. It’s lubricated by the same mix of petrol and two-stroke oil. Here too, the manual for the specific machine applies.

Which petrol to use

Use fresh unleaded petrol from an ordinary filling station.

A guide based on STIHL’s recommendations (check the manual):

• typically 95 octane (a higher octane rating is generally fine)
• according to STIHL, fuels containing ethanol, both E5 and E10, are suitable for STIHL petrol machines
• only buy as much petrol as you’ll use within a short time

What not to do: don’t use old petrol, don’t mix ‘by eye’ and don’t use a higher ethanol content than the manual allows. If the fuel at the pump changes and the machine runs differently, carburettor adjustment is a job for the workshop.

Which two-stroke oil for STIHL engines

Use a good-quality two-stroke oil.

Recommendation:

• preferably STIHL two-stroke oil intended for that use
• or a good-quality two-stroke oil of TC classification, if the manual and STIHL allow it

Never use four-stroke car engine oil or an unknown oil without a TC rating. According to STIHL, cheap oil can damage the engine, seals, fuel lines and tank. We’ll check the availability of STIHL oils in the shop.

How to mix the fuel safely

1. Get a clean can approved for fuel.
2. First pour in the measured amount of oil.
3. Then add the measured amount of fresh petrol.
4. Close the can tightly and shake it so that the oil mixes evenly with the petrol.
5. Before refuelling, open the can carefully. Pressure may have built up inside.
6. Write the date of mixing on the can.

Only mix as much fuel as you’ll use in the next few days or weeks. Not ‘a supply for the whole season’.

Refuelling: safety first

Petrol is flammable. Switch off the engine completely and let it cool down. Refuel in a well-ventilated place, don’t smoke and keep away from naked flames. After refuelling, start the machine at least 3 metres away from where you refuelled, as STIHL usually specifies. Open the cap carefully because of the pressure, don’t spill fuel and don’t let dirt get into the tank. Never refuel a hot engine.

Freshness and storage of your own mix

A mix you make yourself with pump fuel doesn’t keep indefinitely.

STIHL’s recommendation (as a guide):

• store your own two-stroke mix for no longer than about 30 days
• the aim is to reduce the risk of separation (the oil and petrol separating) in fuels containing ethanol
• moisture binds to the ethanol and settles out. The oil is then no longer evenly distributed in the mix
• separated fuel is no longer fit to use, even after vigorous shaking

In practice: mix small batches and keep the can somewhere cool, dry and dark, away from children and naked flames. Shake an older mix (still within the limit) before use. Once it’s past the limit, don’t put it in the machine, and dispose of it according to the rules for fuels.

Long breaks and laying up for winter

With your own mix, before a long break, pour the fuel back into the can if possible, then, outdoors or in a well-ventilated place, away from naked flames and sparks, let the machine run at idle until the fuel system runs dry and the engine stops. Don’t open the throttle fully just to ‘force out’ the remaining fuel. Follow the manual. Never leave the engine running in an enclosed space (risk of carbon monoxide). Clean the machine and store it somewhere dry so that months-old ethanol fuel isn’t left sitting in the carburettor.

Ready-mixed fuel such as STIHL MotoMix

If you’d rather not bother with measuring and the short shelf life of a mix made with pump fuel, consider the ready-mixed special fuel STIHL MotoMix (or the current equivalent in the STIHL range, which we’ll confirm in the shop).

What STIHL usually states about this type of fuel (as a guide, check the label):

• it’s a ready-made mix at a ratio of 1:50 for STIHL two-stroke engines (2-MIX) as well as for STIHL 4-MIX four-stroke engines, which also run on the mix
• it’s a special (alkylate) fuel with a very low ethanol content compared with ordinary pump fuel
• it contains high-quality STIHL oil (the documentation associates it with the HP Ultra range)
• in its unopened original packaging and stored correctly, STIHL states a shelf life of up to about 5 years (cool, dry, dark, typically up to about 20 °C)
• once opened, the information on the label and STIHL’s current instructions apply. Don’t rely on ‘memory’: check the date and the instructions on the packaging

MotoMix is a convenient choice for occasional work, a holiday cottage or a seasonal machine, where a mix made with pump fuel would age between weekends. We’ll confirm availability and pack sizes in person at Zakservices. We don’t list invented part numbers or prices here.

Common mistakes to avoid

What to do if you’ve filled up with the wrong mix

1. Don’t start the machine and don’t work with it.
2. Carefully transfer the mix back into the can (use a funnel).
3. Fill the tank with the correct mix.
4. If the machine won’t start, the spark plug may need checking, or the machine may need servicing.

Running the engine briefly on the wrong mix ‘just to be sure’ won’t save it. If anything, it puts it at risk.

Table: at a glance

Safety and disposal

Store fuel away from children and naked flames. Don’t pour an old mix down the drain or onto the ground. Dispose of it according to the rules of your local authority or collection point. Replace a damaged fuel can, and wear PPE suited to the type of tool when working. If the manufacturer’s manual says something different from this article, the manual applies.

When to come to Zakservices

Come to our shop and workshop in Senica when:

• you don’t know which oil or ready-mixed fuel to use for your STIHL model
• after old fuel, the machine is hard to start, runs unevenly or smokes
• you want the carburettor, spark plug or fuel lines checked
• you need advice on getting the machine ready for winter
• as well as STIHL, you also have STIGA, WOLF-Garten, Cub Cadet, SUPA TECHNIKA or DAKR petrol machinery and want to keep the right procedures for two-stroke and conventional four-stroke engines apart

Bring the model and rating plate details with you, or take a photo of them. We’ll check stock of oils and MotoMix with you in person.

Frequently asked questions (FAQ)

1. What is the correct oil-to-petrol ratio for STIHL two-stroke engines?

As a guide, often 1:50 (1 part oil to 50 parts petrol) with STIHL oil or a good-quality TC oil. Always take the exact figure from the manual for your model.

2. How much oil should I add to 5 litres of petrol?

At a ratio of 1:50, that’s 100 ml of oil to 5 litres of petrol. Check that your manual confirms this ratio.

3. Can I use E10 petrol?

According to STIHL, both E5 and E10 fuels are suitable for STIHL petrol machines. Still, always use fresh petrol and the right oil. See the manual for details.

4. How long does a mix made with pump fuel keep?

STIHL recommends storing your own two-stroke mix for no longer than about 30 days. Don’t use it once it has separated.

5. What is STIHL MotoMix and when is it worth it?

It’s a ready-made special fuel mixed at 1:50 for STIHL two-stroke engines, with a longer shelf life in its original packaging. It’s worth it for occasional work and longer breaks. We’ll check availability in Senica. The information on the label takes precedence.

6. Can I use car engine oil in the mix?

No. Only two-stroke oil belongs in the mix (STIHL or a good-quality TC oil, as the manual says).

7. Does the same mix apply to STIHL 4-MIX too?

In principle, yes: the 4-MIX is lubricated by a mix of petrol and two-stroke oil (often 1:50). It isn’t a car-style engine with separate oil changes. Check the manual for your model.

8. What if I’ve filled up with the wrong ratio?

Don’t start the machine. Drain the mix, fill up with the correct one and, if you have trouble starting, have the spark plug checked or the machine serviced.

9. Should I leave the tank full over winter?

With your own mix made with pump fuel, it’s safer to empty the tank before a long break and run the fuel system dry as the manual says. With a ready-mixed special fuel such as MotoMix, the manufacturer’s information and the label apply. If in doubt, ask us in the shop.

10. Will shaking an old mix help after two months?

If it has already separated, no. STIHL points out that such fuel is no longer in perfect condition, even after vigorous shaking. Mix a fresh batch or use a suitable ready-mixed fuel.

Let us help you at Zakservices in Senica

If you’re unsure about the ratio, the choice of oil, how long a mix keeps or getting your STIHL chainsaw or brushcutter ready for the season, come in with the type of machine and a short description (hard starting, smoke, uneven running, old fuel). At Zakservices in Senica, we’ll advise you on oil, MotoMix and a safe procedure in line with the manual and our current stock.

Zakservices, s.r.o.
Obchodná 493/2A, 905 01 Senica (white building opposite the Kaufland car park)
Phone: +421 904 446 915, +421 34 651 70 72
Email: zakservices@zakservices.sk
Website: https://www.zakservices.sk

We’ll check specific oils, ready-mixed fuels and availability with you in person.