Ethanol is in most of the gasoline sold in Canada, and E85 is a popular choice for turbo and flex-fuel builds. Ethanol isn't bad for a healthy fuel system, but it behaves differently from straight gasoline in ways that matter for fuel injectors: it cleans, it attracts water, and at E85 levels it needs a lot more fuel flow. Here's what each of those means and how to keep your injectors in good shape.
E10, E15 and E85: what the numbers mean
The number after the E is the approximate percentage of ethanol in the blend. E10 is up to 10% ethanol and 90% gasoline — the kind of fuel most daily drivers burn without thinking about it. E85 is a high-ethanol blend (the actual ethanol content can vary by season and supplier) meant for flex-fuel vehicles and engines tuned for it. Ordinary vehicles are built for low blends like E10; only flex-fuel vehicles or properly converted and tuned engines should run E85.
Effect 1: ethanol is a solvent
Ethanol dissolves and loosens deposits that gasoline leaves alone. In a clean system that's a small benefit. In an older vehicle, or one that has run on old fuel, ethanol can loosen varnish and debris from the tank and lines. That loosened material travels downstream to the fuel filter — and whatever gets past the filter ends up at the injector inlet screens and nozzles.
This is why problems sometimes appear right after a change in fuel: switching an older engine to an ethanol blend, or the first few tanks of E85 after a conversion. The fix is simple: replace the fuel filter after the switch, and if symptoms appear, check the injectors rather than assuming the new fuel "doesn't agree" with the engine.
Effect 2: ethanol attracts water
Ethanol absorbs moisture from the air. In a vehicle that's driven regularly this isn't a concern — the fuel is used before much water builds up. In a vehicle that sits for months, the ethanol can pull in enough water that the water-ethanol mix separates from the gasoline and settles at the bottom of the tank. That's called phase separation.
Water and separated fuel are hard on injectors. Water doesn't lubricate, it can promote corrosion on internal steel parts, and a slug of it through the injectors means a rough-running or non-starting engine. Seasonal vehicles are most at risk — see our winter storage guide for fuel injectors for how to prepare a car, boat or sled.
Effect 3: E85 needs much more fuel flow
Ethanol contains less energy per litre than gasoline, so the engine needs more of it to make the same power. Tuners commonly plan for roughly 30–40% more fuel volume on E85 compared with gasoline. That has two consequences for injectors:
- Size. Injectors that were comfortable on gasoline may run out of capacity on E85, especially on a boosted engine. Our injector sizing guide shows the formula and the BSFC values typically used for E85.
- Balance matters more. When injectors run near the top of their range, a small difference between cylinders becomes a bigger share of the fuel delivered. One injector flowing less than the others can leave that cylinder lean under load. A matched, balanced set takes that risk off the table.
The pump, lines and regulator have to keep up too. If you're building for E85 or flex fuel, look at the whole system — our fuel systems and flex-fuel kits and fuel pumps are a good place to start.
Cold starts on E85
Ethanol doesn't vaporize as easily as gasoline in cold weather, so high-ethanol blends are harder to start when it's cold. Fuel suppliers often adjust E85 blends seasonally for this reason, and flex-fuel tunes add extra cold-start fuel. If an E85 car is hard to start on a cold morning, the fuel itself is a likely factor. But a hard start combined with a rough idle once warm, or a misfire on one cylinder, deserves a look at the injectors.
Are your injectors ethanol-compatible?
Most modern factory injectors are designed to handle low ethanol blends. For E85, use injectors the manufacturer lists as suitable for ethanol, and make sure the O-rings and seals are too. Older injectors and seals were not always designed with high ethanol content in mind. When you change seals, use ones rated for the fuel you're running.
Signs ethanol has caused an injector problem
- Rough idle or misfires that started after a change in fuel or a long period of storage
- Lean codes (P0171/P0174) on an E85 or flex-fuel tune — see our lean codes guide
- One cylinder running hotter or leaner than the rest on a wideband or per-cylinder data
- A fuel filter that clogs quickly after the switch
How cleaning and flow testing helps
Off-car ultrasonic cleaning removes the varnish and debris that additives may not shift, and a flow test shows how each injector actually performs. At Budget Injector, every injector gets an ultrasonic cleaning and a flow test after cleaning, with a printed flow sheet covering spray pattern, leak check and balance across the set. Add before-cleaning numbers and you can see exactly how much the cleaning changed. If one injector won't come back in line, you know to replace just that one — or step up to a new injector set sized for E85.
What it costs
$15 per injector for ultrasonic cleaning and a flow test after cleaning. Add $5 per injector for before-cleaning flow numbers, a reverse flush, or GDI/diesel injectors. Pay at pickup; typical turnaround is 1–2 hours at our Clayton, Surrey shop, a short drive from Langley and White Rock and South Surrey. Book your cleaning.
Related: how to read a flow test · fuel injectors and winter storage · testing used injectors