Echo Weed Eater Gas Oil Ratio: SRM-225, GT-225, PAS-225

The Echo weed eater gas oil ratio is 50:1 for every gas trimmer Echo currently sells. That is 2.56 oz of 2-stroke oil per US gallon of gas, or 20 ml per litre. It does not matter whether the tool says SRM, GT or PAS on the shaft, whether it is a homeowner model or an X Series professional unit, or which attachment is on the end. The questions that do need answering are the ones this guide covers: how much oil goes in the size of can you actually own, what gas Echo wants, what to do with an older Echo whose manual says something else, and why a trimmer that was mixed correctly still refuses to start.

Every Echo trimmer, one ratio

Echo sorts its handheld trimmers into three families, and the letters tell you the shaft, not the fuel:

Family	What it is	Common models	Mix
SRM	Straight-shaft trimmer and brushcutter	SRM-225, SRM-225i, SRM-2620, SRM-266, SRM-3020T, SRM-410	50:1
GT	Curved-shaft trimmer	GT-225, GT-225i	50:1
PAS	Pro Attachment Series powerhead	PAS-225, PAS-2620, PAS-266	50:1

The number after the letters is roughly the displacement: a 225 is a 21.2 cc engine, a 2620 is a 25.4 cc engine, and so on up the range. The SRM-225, GT-225 and PAS-225 share the same engine and even the same fuel tank part, which is why so many of the model-specific questions about them have identical answers. Echo’s own specification for the SRM-225 lists a 0.38 litre (12.8 US fl oz) fuel tank, a 50:1 gasoline to oil ratio, and an oil rated ISO-L-EGD or JASO M345-FD.

A full tank on a 225 holds about a quarter of an ounce of oil. That is a small enough amount that the ratio is only ever as accurate as the batch you mixed in the can, which is why the measuring step below matters more than which brand of oil you pick.

How much oil for the can you own

Echo sells Power Blend X in 2.6 oz single-use bottles, each sized to treat one US gallon. That is a hair richer than a true 50:1 (it works out closer to 49:1), which is harmless and a sensible rounding. The trouble starts when the gas can is not one gallon. Here is the oil for the batch sizes people actually mix:

Fuel	Oil at 50:1
1 US gallon	2.56 oz
2 US gallons	5.12 oz
2.5 US gallons	6.4 oz
5 US gallons	12.8 oz
1 litre	20 ml
5 litres	100 ml

The classic mistake is dropping a whole 2.6 oz bottle into a half-full one-gallon can. That is 25:1, twice the oil Echo asks for, and the trimmer will tell you with blue smoke, a wet plug and a clogged spark arrestor screen within a few tanks. The opposite mistake, one bottle into a 2.5 gallon can, is about 123:1 and is the one that scores a cylinder. For odd amounts, use the calculator; it is preset to Echo’s ratio:

Fuel → oil / Oil → fuel

Fuel → oil Oil → fuel

Amount of fuel

Gallons (US) Litres

Equipment (optional) Choose equipment… Chainsaw (50:1) String trimmer / weed eater (50:1) Leaf blower (50:1) 2-stroke lawn mower (50:1) Dirt bike / motorcycle (40:1) Outboard motor (50:1)

Mix ratio

100:1 50:1 40:1 32:1 25:1 20:1

Custom ratio (X : 1)

Calculate Reset Copy link to this mix

Add this much oil

12.8 oz

≈ 378.54 ml

Add 12.8 oz of 2-stroke oil to 5 gal of gas at a 50:1 ratio.

If you mix in anything other than one-gallon batches, a proper measuring cup or a marked oil bottle removes the guesswork. The measuring tools guide covers which ones are worth buying, and the 50:1 chart has the full table from a pint to five gallons.

What gas Echo actually wants

The oil gets all the attention, but the gas is where Echo trimmers most often go wrong. Echo’s fuel guidance is specific:

• 89 octane or higher. Echo does not recommend regular 87, both for detonation margin in a hot small engine and because the mid-grade and premium blends tend to carry more detergent.
• No more than 10 percent ethanol. E10 is the ceiling. E15 and the E85 pump next to it will damage fuel lines, the primer bulb and the carburettor diaphragms.
• Fresh fuel. A trimmer is used in short bursts a few times a month, so the same can often sits for six weeks or more. Mix what you will use in about a month, or add a stabiliser. Power Blend X already contains one, which is one of its genuine advantages.

For a trimmer that sits for most of the year, the easiest answer is Echo’s Red Armor canned fuel, which is ethanol free and already mixed at 50:1. It costs several times what pump gas does, but a homeowner trimmer burns so little that the difference over a season is small, and it removes stale fuel as a cause of hard starting.

Older Echos and the 32:1 manual

If you inherited an Echo from the 1980s or 1990s, the manual may say 32:1, and a few very old units said 16:1. That was the norm for the oils of the time, not a quirk of the engine. Echo now states that its older air-cooled engines can run 50:1 on a modern 2-stroke oil, even where the original manual gave a richer figure.

The practical rule: with a current JASO FD or ISO-L-EGD oil (Power Blend X, Red Armor, or any of the substitutes in the Echo oil guide), run 50:1. With a bargain bottle that carries no rating, stay at the ratio in the old manual. What you should not do is run an old trimmer at 50:1 on unrated oil, which gets you the least protection from both directions. If you are unsure what the ratings mean, TC-W3 vs JASO FD explains them, and the 32:1 page has the quantities if you stay rich.

The PAS question

The Pro Attachment Series causes more confusion than the ratio itself. A PAS powerhead takes a trimmer head, edger, pole saw, hedge trimmer, brush cutter or cultivator, and people reasonably wonder whether a heavy attachment changes the mix. It does not. The ratio belongs to the engine. A PAS-225 runs 50:1 whether it is edging a driveway or carrying a pole saw into a tree, so one can of mix serves every attachment you own. The same goes for the rest of the Echo shed: Echo’s chainsaws and leaf blowers are 50:1 as well, so a single can runs the lot.

When the mix is right and it still will not start

Most Echo trimmers that arrive at a repair counter “because of the mix” have a different problem. Worth checking before you blame the ratio:

1. Stale fuel. Pour the tank out and refill with fresh 50:1. If it starts, you have your answer.
2. The primer bulb. Press it until fuel is visible in the bulb, usually six or more presses. A cracked bulb that will not refill is a common, cheap failure.
3. The spark arrestor screen. It sits behind a small cover on the muffler and clogs with carbon, faster if the mix has been rich. A clogged screen shows up as a trimmer that starts but will not rev under load.
4. The air filter. Trimmers run in their own dust cloud. A loaded filter makes the engine run rich regardless of what is in the tank.
5. The fuel filter and line. Ethanol hardens them over a few seasons. A trimmer that revs up and then dies is often starving at the pickup.

The seasonal version of this checklist, for a trimmer coming out of winter storage, is in spring startup for 2-stroke lawn equipment. For the general routine of mixing a can properly, see how to mix 2-stroke fuel, and for trimmers from other brands, the string trimmer mix page covers Husqvarna and the budget models that do not run 50:1, and Stihl owners get the model-by-model version, 4-MIX included, in the Stihl weed eater gas mix guide.