Why You Should Never Use E15 or Unleaded 88 Gas in Your Portable Generator

Published for US customers

E15 gasoline is now widely available at fuel stations across the United States, and more Americans are accidentally pumping it into their portable generators, pressure washers, lawn mowers, and other small engine equipment every single day.

Here is the problem: E15 is not approved for use in portable generators or any small engine equipment. Using it can — and does — cause serious, expensive damage to your engine and fuel system.

In this guide we explain exactly what E15 is, why it damages small engines, what fuel you should be using, and most importantly — what to do if you have already put E15 in your generator.

If you need help right now, our team of Generator Engineers is available FREE of charge:
? Contact our engineers free at generatorguru.com/need-help

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⚠️ Important Safety Warning

⚠️ SAFETY FIRST — Read Before Handling Fuel

Gasoline is highly flammable. Always handle fuel outdoors or in a well-ventilated area. Never refuel a hot or running engine. Keep fuel away from sparks, open flames, and heat sources. Store fuel in approved containers only. Never run a generator indoors or in an enclosed space — carbon monoxide from exhaust fumes is odourless, colourless, and can kill within minutes. Always operate generators outdoors, at least 20 feet (6 metres) from doors, windows, and vents.

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What Is E15 Gasoline?

Gasoline sold in the United States is blended with ethanol — a grain-based alcohol added to extend fuel supply and reduce certain emissions. The number after the letter "E" tells you the percentage of ethanol in the blend:

• E0 — Pure gasoline. Zero ethanol content. Also called ethanol-free gas.
• E10 — 10% ethanol, 90% gasoline. The most common blend at US pumps for decades.
• E15 — 15% ethanol, 85% gasoline. Newer, increasingly available at stations across the US.
• E85 — 85% ethanol. For flex-fuel vehicles only. Never use in generators.

E15 became more widely available following EPA waivers and federal policy changes encouraging higher ethanol blends. As of 2024, thousands of US fuel stations now offer E15 — often labelled as "Unleaded 88" at the pump. The name "Unleaded 88" refers to its octane rating, and it does not make it immediately obvious that the ethanol content is higher than standard E10.

This is where the problem starts. Many generator owners fill up at the pump without realising they have selected Unleaded 88 / E15 instead of their usual regular unleaded E10.

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Is E15 Approved for Use in Portable Generators?

No. Absolutely not.

The US Environmental Protection Agency (EPA) does NOT approve E15 for use in:

• Portable generators
• Lawn mowers
• Pressure washers / power washers
• Chainsaws and outdoor power equipment
• Motorcycles
• Off-road vehicles
• Boats and marine engines
• Any engine or fuel system not specifically designed for E15

E15 is only approved by the EPA for use in model year 2001 and newer passenger cars and light trucks. Portable generators are explicitly excluded.

The Outdoor Power Equipment Institute (OPEI), small engine manufacturers, and generator manufacturers all recommend a maximum of E10 — and ideally E0 (ethanol-free gasoline) — for the best engine performance and longevity.

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Why Does Ethanol Damage Small Engines?

Small engines used in generators, pressure washers, and outdoor equipment were designed and manufactured before high-ethanol blends became standard. Their fuel systems use materials — rubber, aluminium, brass, zinc, and certain plastics — that ethanol attacks aggressively.

Here is exactly what ethanol does inside your generator's fuel system and engine:

1. Ethanol Absorbs Water (Phase Separation)

Ethanol is hygroscopic — it absorbs moisture from the air. As fuel sits in your generator's tank (especially during storage), ethanol draws in atmospheric moisture. When enough water accumulates, a process called phase separation occurs: the ethanol and water separate from the gasoline and sink to the bottom of the fuel tank as a corrosive water-ethanol layer.

When your engine draws fuel from the bottom of the tank, it ingests this water-ethanol mixture. The results are:

• Engine misfires and loss of power
• Corrosion inside the fuel tank, carburettor, and fuel lines
• Engine damage from running on water-contaminated fuel
• Complete engine failure in severe cases

Higher ethanol content (for example E15 vs E10) accelerates this process significantly. E15 absorbs water faster and reaches phase separation sooner.

2. Ethanol Corrodes Carburettor Components

The carburettor is the most vulnerable component in your generator's fuel system. Inside a carburettor, tiny jets, needles, and passages measure and mix fuel with air with extraordinary precision. Some of these passages are as small as 0.3mm in diameter.

Ethanol:

• Corrodes aluminium carburettor bodies (turns white and pits the metal)
• Dissolves zinc alloy components (zinc carbide deposits form and block jets)
• Attacks brass needle valves and jets
• Leaves varnish and gum deposits when it evaporates (clogs jets and passages)

The higher the ethanol percentage, the faster this damage occurs. E15 is significantly more aggressive than E10, and far more aggressive than E0.

A carburettor damaged by ethanol typically requires a full rebuild or replacement. Carburettor rebuilds cost between $45-$120 in parts alone — and on Chinese-made and budget generators, replacement carburettors are often the only practical solution.

3. Ethanol Degrades Fuel Lines and Seals

Generators and small engine equipment use rubber fuel lines and carburettor gaskets that were not formulated to withstand ethanol exposure. Ethanol:

• Causes rubber fuel lines to swell, soften, and crack
• Dissolves fuel line inner linings, sending debris into the carburettor
• Hardens and cracks carburettor gaskets (causing air leaks and fuel leaks)
• Degrades fuel tap diaphragms and O-rings

The result is fuel leaks, vacuum leaks, and carburettor flooding — all of which make your generator difficult or impossible to start.

4. Ethanol Reduces Fuel Energy Content

Ethanol contains approximately 34% less energy per gallon than pure gasoline. This means:

• Your generator runs on a leaner fuel mixture than it was tuned for
• Engines running lean run hotter than designed
• Lean running accelerates valve wear, piston wear, and cylinder wear
• Fuel consumption increases (more fuel needed to produce the same power)
• Engine may surge, hunt, or struggle to maintain stable RPM under load

The jump from E10 to E15 represents a 50% increase in ethanol content — a significant change that the fuel system and engine calibration of most generators cannot handle without consequences.

5. Ethanol Dissolves Old Deposits — Then Re-Deposits Them

In a generator that has been running on E10 for years, ethanol will have gradually loosened and dissolved old varnish and gum deposits inside the fuel tank. When you switch to E15, the higher ethanol content dislodges these deposits faster and carries them through the fuel system — directly into the carburettor jets, needle valve seat, and fuel filter.

The result is a suddenly blocked carburettor on a generator that was previously running fine.

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What Fuel SHOULD You Use in Your Generator?

The answer is straightforward:

✅ First Choice: E0 — Ethanol-Free Gasoline (Pure Gas)

E0 is pure gasoline with zero ethanol content. It is the safest, cleanest fuel for portable generators and all small engine equipment. Benefits of E0:

• No ethanol to absorb moisture — eliminates phase separation risk
• No ethanol to corrode carburettor components
• No ethanol to degrade rubber fuel lines and gaskets
• Higher energy content (more power per gallon)
• Stays usable in storage far longer than E10 or E15
• Significantly reduces the risk of carburettor problems

Where to find E0 in the USA:

E0 is available at select fuel stations across the country. The best resource for locating ethanol-free gas near you is:

• pure-gas.org — A comprehensive, user-maintained map of ethanol-free fuel stations across the USA and Canada. Search by zip code or city to find your nearest E0 source.

E0 is often slightly more expensive per gallon than E10, but the money saved in carburettor repairs, fuel line replacements, and avoided engine damage makes it excellent value for generator owners.

✅ Second Choice: E10 — Maximum 10% Ethanol

If E0 is not available near you, E10 can be acceptable for most modern generators when used with a quality fuel stabilizer, especially for seasonal or standby generators that may sit unused for months at a time. E10 is the maximum ethanol blend recommended by the vast majority of generator manufacturers.

If using E10:

• Always add a quality fuel stabilizer (Sta-Bil, Sea Foam, or similar)
• Do not store fuel in the tank for more than 30 days without stabilizer
• With stabilizer, treated E10 can last 12-24 months
• Drain the carburettor if storing generator for longer periods

❌ Never Use: E15 (Unleaded 88), E85, or Any Blend Above E10

• E15 / Unleaded 88 — Not EPA approved for generators or small engines. Causes the damage described above.
• E85 — Never use in any generator. Will destroy your fuel system rapidly.
• Any ethanol blend above E10 — Not suitable for small engines regardless of octane rating labelling.

⛽ Watch for "Unleaded 88" at the pump. Many US fuel stations label E15 as "Unleaded 88" based on its octane rating rather than its ethanol content. The name makes it sound like regular gasoline. Always check the small print on the pump label for ethanol content before filling any generator, lawn mower, pressure washer, or other small engine equipment.

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How to Read a Fuel Pump Label

At any US fuel pump, look for the ethanol content disclosure on the pump face or nozzle. Federal regulations require ethanol content to be disclosed, but the labelling can be easy to miss:

• "Ethanol Free" or "No Ethanol" — This is E0. Best choice for generators.
• "Contains up to 10% Ethanol" — This is E10. Acceptable for generators, but not the perfered.
• "Contains up to 15% Ethanol" or "Unleaded 88" — This is E15. Do not use in generators.
• "Flex Fuel" or "E85" — Never use in generators.

When in doubt, look for the small yellow label on the pump nozzle. If it says "E15" or "Contains up to 15% ethanol" — do not use it in your generator.

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Symptoms of E15 Damage in Your Generator

If you have already used E15 in your generator — accidentally or unknowingly — watch for these warning signs:

Immediate Symptoms (Within First Few Tank Fills)

• Engine runs rough or surges up and down at idle
• Generator lacks power under load
• Engine hesitates or stumbles when throttle is increased
• Increased fuel consumption
• Engine runs hotter than normal

Short-Term Symptoms (After Several Tank Fills)

• Carburettor flooding — fuel overflowing from air filter
• Hard starting — takes many pulls to start
• Engine starts but dies after a few minutes
• Engine only runs with choke partially closed
• Visible fuel leaks from carburettor area
• Fuel smell from engine area (degraded fuel lines)

Long-Term Symptoms (Extended E15 Use)

• Engine will not start at all
• Carburettor jets completely blocked with varnish or white deposits
• Cracked or collapsed fuel lines
• Corroded fuel tank interior
• Damaged piston rings from lean running (blue/white smoke from exhaust)
• Engine knock from lean combustion damage

If you are experiencing any of these symptoms after using E15 or Unleaded 88, please contact our Generator Engineers immediately for free diagnosis and advice:

? generatorguru.com/need-help

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? Used E15 by mistake? Our team can help.

Our qualified Generator Engineers provide FREE diagnosis and repair guidance. Send us a message and describe what happened — we will walk you through exactly what needs doing.

? Get free help at generatorguru.com/need-help

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Fuel Storage Best Practices for Generator Owners

Most generator problems — not just ethanol damage — come down to fuel storage. Follow these practices to keep your generator ready when you need it:

Short-Term Storage (Under 30 Days)

• Use E0 or fresh E10 from a busy fuel station (high turnover)
• Keep tank between half and full (reduces condensation space)
• Store generator in a cool, dry location

Seasonal Storage (30 Days to 12 Months)

• Add a quality fuel stabilizer before storage
• Run engine for 10 minutes after adding stabilizer (distributes throughout system)
• Use E0 if possible (stabilized E0 stores longer than stabilized E10)
• Consider draining carburettor float bowl for long-term storage

Long-Term Storage (Over 12 Months)

• Use high-quality fuel stabilizer rated for 24-month protection
• Preferred method: Drain fuel tank and carburettor completely before storage
• Draining prevents varnish deposits entirely
• Add fresh fuel when generator is returned to service

Fuel Container Storage

• Never store fuel in unapproved containers
• Use red, sealed, vented safety cans rated for gasoline
• Date your fuel containers — discard fuel older than 30 days (untreated) or per stabilizer instructions (treated)
• Store in a cool, shaded location away from living areas

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What About Oil? What Should I Use in My Generator?

Since you are maintaining your generator's fuel system, it is worth a reminder about oil as well.

Always use mineral (non-synthetic) engine oil in portable generators.

• SAE 30 — For temperatures above 40°F (4°C). Standard warm-weather choice.
• 10W-30 mineral oil — For variable or cooler temperatures. Good year-round choice in most US climates.

Never use synthetic or semi-synthetic oil in portable generators unless specifically approved by the manufacturer. Synthetic oil can cause excessive oil consumption and sealing issues in generator engines not designed for it.

Check oil level before every use and change oil every 50 hours or once per season. Find the correct oil capacity for your specific generator model on the oil product listing for your model at generatorguru.com.

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Generator Parts Damaged by E15 — What You May Need

If E15 has damaged your generator's fuel system, here are the parts most commonly required. Find the correct parts for your specific generator model at generatorguru.com — select your brand and model to see all compatible parts:

Part	Why May Be Needed After E15 Damage	Typical Cost (USD)
Carburettor	Corroded jets, blocked passages, damaged float needle	$12 - $65
Carburettor rebuild kit	Gaskets, needle, float, jets — rebuild instead of replace (skilled repair, suggested for Pros only )	$6 - $20
Fuel lines	Swollen, cracked, or degraded rubber lines	$4 - $15
Fuel filter	Blocked by debris dislodged by ethanol	$4 - $10
Fuel tap / petcock	Degraded internal diaphragm and seals	$6 - $20
Spark plug	Fouled from rich/lean running issues	$4 - $10
Air filter	If has been fuel-soaked from carburettor flooding	$5 - $15
Fuel tank	Internal corrosion from phase separation (severe cases - check for rusting inside tank)	$25 - $180

? Find the correct parts for your generator model at generatorguru.com

Select your generator brand and model to see all compatible parts. We stock over 1 million parts for 12,000+ generator models — including the full range of Chinese-made and budget generators that other suppliers don't stock.

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Frequently Asked Questions

Can I use Unleaded 88 in my generator?

No. Unleaded 88 is the marketing name for E15 — gasoline containing 15% ethanol. It is not approved by the EPA for use in portable generators or any small engine equipment. Use E0 (ethanol-free) or E10 only.

I accidentally used E15 once. Is my generator ruined?

One accidental fill-up is unlikely to cause catastrophic damage, but it is not harmless either. We will walk you through exactly what needs doing. 

? Get free help at generatorguru.com/need-help

Where can I find ethanol-free E0 gasoline near me?

Visit pure-gas.org and search by your zip code. This community-maintained database lists ethanol-free fuel stations across the USA and Canada.

Does fuel stabilizer protect against ethanol damage?

Fuel stabilizer helps prevent the varnish and gum deposits that form as fuel ages, and it helps slow moisture absorption. However it does not eliminate the corrosive properties of ethanol entirely. E0 with stabilizer is the gold standard for generator fuel storage. E10 with stabilizer is acceptable. E15 with stabilizer is still not appropriate for generators.

My generator runs fine on E15 — should I still switch to E0?

Yes. Ethanol damage is often cumulative and not immediately obvious. The carburettor may appear to function normally while corrosion is gradually building up inside. By the time symptoms appear, significant damage may already have been done. Switch to E0 or E10 now and save yourself an expensive repair later.

Does Generator Guru sell parts for Chinese generator brands?

Yes — this is one of our specialties. We stock parts for Loncin, Lifan, Kipor, Kama, and all common Chinese engine series including the 168F, 170F, 188F, and 192F engines used in hundreds of budget generator brands. If you can't find your brand elsewhere, we almost certainly have it. Browse all brands at generatorguru.com.

My generator won't start after using the wrong fuel. What should I do?

We will walk you through exactly what needs doing. 

? Get FREE help at generatorguru.com/need-help

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The Bottom Line

E15 / Unleaded 88 is appearing at more US fuel stations every year, and the risk of accidentally using it in a generator, lawn mower, or pressure washer is real and growing.

The rules are simple:

• ✅ E0 (ethanol-free) — Best choice. Use it whenever you can find it.
• ✅ E10 — Acceptable. Use with fuel stabilizer, especially for stored fuel.
• ❌ E15 / Unleaded 88 — Never use in generators or small engines.
• ❌ E85 — Never use in generators under any circumstances.

If you have already used E15 by mistake, drain your fuel system, inspect your carburettor and fuel lines, and contact our engineers for free guidance.

Generator Guru stocks over 1 million parts for 12,000+ generator models — including all the fuel system components most commonly damaged by ethanol. Whether you need a carburettor, fuel lines, a fuel tap, or a complete rebuild kit, find the right part for your specific model at:

? generatorguru.com

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