Is Starting Fluid Bad for Gas Engines?

John Baker|May 22, 2017 8:08 AM

The simple answer: In small doses and used properly, it can be effective in hard-starting gasoline engines. But it can be bad for two-stroke or diesel engines. The real question to ask is, “Why does my engine need starting fluid in the first place?” Find out the answer, then fix the real problem.

The detailed answer: Ask five gearheads or mechanics their opinion of starting fluid, and you might get five different answers.

Some occasionally use it to help revive an engine that’s been pulled from storage. Others use it to help coax a stubborn engine to life on a frigid morning.

Yet others won’t touch starting fluid. One mechanic I talked to blamed starting fluid for ruining the bearings in a two-stroke outboard motor. Its owner, the story goes, liberally sprayed starting fluid into the intake when the engine wouldn’t start. And sprayed. And sprayed.

Starting fluid typically contains ether, which is an effective solvent. In this case, the starting fluid likely washed the inside of the engine clean of oil, allowing metal components to contact and eventually seize.

Diesel engines, too, can suffer the effects of starting fluid. Their high compression can cause the fluid to ignite too early, effectively causing pre-ignition, which invites all kinds of problems, like catastrophic piston or rod damage. Plus, it has no lubricating properties, so it can hasten piston wear.

With minimal work, you can find all sorts of cautionary tales on the Internet of people blowing up engines after using too much starting fluid.

Starting Fluid Does Sometimes Work

Given the disdain many harbor toward starting fluid, why would anyone use it?

Because it can be effective in gasoline engines – especially carbureted engines – when used as directed.

For gasoline to combust, it must first be vaporized. The fuel injectors in your car or truck do a great job of completing this task.

In carbureted engines, fuel is vaporized as it’s forced through the tiny openings or nozzles in the carburetor. But carburetors don’t vaporize fuel as effectively as fuel injectors. Plus, gasoline doesn’t vaporize as readily when it’s cold. Anyone who’s started a carbureted car on a frigid morning knows this all too well. Plus, an engine requires more gas in the fuel/air mixture at startup, making a cold engine doubly difficult to start and keep running.

Starting fluid, on the other hand, does readily ignite in the cold, helping to start the engine and generate heat to more easily vaporize the fuel.

But a little goes a long way. Many of the problems with starting fluid can be attributed to operator error rather than the fluid itself.

In short, if you have to use starting fluid, use it sparingly. If a couple short bursts of spray into the intake don’t elicit a cough or two from the engine, emptying the can isn’t going to work, either.

No amount of starting fluid is going to revive an engine with a dirty carburetor. Identify the real problem and get it fixed.

Ask yourself this…

Instead, ask yourself why the engine needs starting fluid in the first place. There’s likely a bigger problem that needs fixing.

I was presented with this exact scenario last fall when my snowblower refused to start. So I reached for a can of starting fluid and gave the intake a shot. She sputtered a few times and quit. I repeated the process a few times, with the same result.

I should have used Quickshot when it was sitting right there when I last filled the tank. Would have solved this issue all together.

Eventually, I took apart and cleaned the carb. She roared to life on the first pull after that. In my case, emptying the entire can of starting fluid into the engine wouldn’t have done a thing, aside from washing the oil from the cylinder and causing wear. At the very least, it helped me diagnose what the problem was not: lack of spark or bad compression.

Bottom line: Starting fluid can help start a stubborn engine, but follow the directions and use it sparingly. If a little bit doesn’t work, a lot likely won’t, either. If your engine is consistently hard to start, find out why and get the real problem fixed.

Low-viscosity doesn’t mean low quality

As motor oil viscosity continues to decrease, base oil and additive quality become more important.

Michael Meuli | VICE PRESIDENT, TECHNICAL DEVELOPMENT

Despite uncertainty surrounding future CAFÉ standards, fuel economy remains the biggest driver of innovation in the auto industry. One strategy for increasing fuel economy involves reducing energy lost to friction. Using lower-viscosity lubricants, which reduce pumping losses and flow easier at startup, helps automakers accomplish this goal. Just as we’ve become accustomed to 0W-20 oils, 0W-16 oil has entered the market and is recommended for the 2018 Toyota Camry and Honda Fit. People are wondering how much lower viscosity can go.

That’s because excessively low lubricant viscosity can reduce wear protection. Some people fear the fuel economy gains of modern low-viscosity oils aren’t worth the potential loss of wear protection. You should be familiar with the relationship between lubricant viscosity and wear protection, but it bears repeating.

Motor oil must develop a durable fluid film that separates engine components so they don’t rub together and wear out. As a rule of thumb, the higher the oil’s viscosity, the thicker the fluid film – and the better the wear protection.

That being the case, you might think it advantageous to throw out your 0W-20 motor oil and use 15W-50 instead. That’s a bad idea, and here’s why.

Modern engines are built with tighter clearances between parts than their predecessors. Let’s take the GM* 3.8L engines we test in our mechanical lab as an example. The clearances between the crankshaft journals and main bearings can be as low as .0007 inches. That’s thinner than a sheet of paper (about .004 inches).

During operation, oil continuously flows through tiny ports in the crankshaft journals to lubricate the journal/ bearing interfaces. It should form a strong, consistent oil film on which the crankshaft journals float as they spin, preventing them from touching the bearings. This is called hydrodynamic lubrication. Oil that’s too thick for the engine, however, may not flow fast enough to fill the clearances, allowing the high spots on metal surfaces to contact. This is called boundary lubrication.

In this case, using a higher viscosity oil than what’s recommended in your modern engine would lead to increased wear. Adding insult to injury, it would reduce fuel economy and increase operating temperatures as well.

Viscosity that’s too low, however, can have the opposite effect. Since viscosity is related to film thickness, low-viscosity oil may not develop an adequate fluid film to keep metal components separated, leading to wear. If bad enough, parts will eventually weld together and destroy the engine.

You can see how modern engines have put oil formulators into a bind. How do we formulate low-viscosity oils that maximize fuel economy while also providing good wear protection in today’s stressful engines?

In a word, quality.

Although oil film thickness is related to lubricant viscosity, film strength is a function of base oil and additive quality. We start with high-quality synthetic base oils that offer naturally high resistance to heat and chemical breakdown.

The challenge, however, is that lower viscosity oils tend to be more volatile, meaning they burn off more easily when exposed to high heat. If you ever look at a motor oil’s NOACK Volatility, you’ll notice volatility tends to increase as the oil viscosity decreases. This is of particular importance since most new vehicles are equipped with turbocharged engines, which generate increased heat. High volatility can lead to excessive oil consumption, which causes the oil to thicken, making it harder to pump through the engine and reducing fuel economy. Oil that has thickened can also lead to deposits and disrupt the additive balance.

That’s why only synthetic base oils can be used to formulate a 0W-16 motor oil. Conventional base oils are too volatile to meet requirements of low-viscosity oil.

Additives, too, play a vital role in low viscosity oils. We talked about boundary lubrication earlier. When in a boundary lubrication situation, protecting against metal-to-metal contact falls on the motor oil’s anti-wear additives, more so than with higher viscosity oils. The additives form a sacrificial barrier on metal parts that absorbs contact and protects the metal surfaces.

Motor oil quality has always been important, but modern low-viscosity oils underscore the point. That’s good news for Dealers selling the best oil on the market.

To help you reach this market, we introduced new OE 0W-16 Synthetic Motor Oil (OES) last month. We’ll monitor demand for 0W-16 oils and introduce additional formulations if demand dictates.

In the meantime, brace yourself for 0W-8 motor oil, which is already being tested in Japan.

Tag: amsoil