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Maintaining Your Argo’s Vanguard Big Block EFI

In the past few years, Argo has gradually switched to Vanguard EFI engines in their amphibious ATVs. These engines are built for extreme duty cycles and low end torque, delivering the reliable performance owners depend on, whether they use an Argo for work or for fun. Here’s what you need to do to make sure your Argo’s engine stays in top shape.

Maintenance Schedule

Maintenance goes by operating hours, not miles. Your Argo has a built in hour meter. Just push the button on the gauge cluster until you see “Hours” on the display.

  • 100 hours: Replace the spark plugs, change the oil and check the air filter
  • 250 hours: Check the valve clearance. This should be done by a service technician.
  • 400 hours: Replace the air filter and fuel filter. Clean the engine and oil cooler fins.


For the widest operating temperature range, stick to synthetic oil. Vanguard recommends their 15W-50 synthetic oil above 20°F. Synthetic 5W-30 works at temperatures below 100°F. Conventional 10W-30 will work in a pinch, but oil consumption can be high in hot weather.

This engine has an oil sensor that shuts off the ignition system when the level is too low. If your engine won’t start, check the oil level.

Oil cannot be removed from the drain plug in these vehicles. You must use a siphon pump to remove oil from the engine. Always change the oil filter when you change the oil. The engine holds about 2.5 quarts of oil, or 78-80 oz.

Air Filter

The filter is under a cover at the top of the engine, which is held on by a thumb screw. Once the cover isoff, you’ll need to remove a wing nut to remove the filter.

Clean the paper filter element by tapping it against a hard surface. Clean the foam pre-filter by washing it in water and a mild detergent, then let it air dry. Do not oil the pre-filter.

Fuel Filter

The gas tank must be empty before removing this filter. Trace the fuel line from the engine to the firewall. You should see the filter. Use a set of pliers to squeeze the hose clamps and pull the hoses off of the filter. Check the lines for cracks and replace them as needed. When you install the new filter, make sure the arrow on the case points toward the engine. Let any spilled fuel evaporate before starting your Argo.

Spark Plugs

The electrode gap on all Vanguard engines is 0.030 inches or 0.76 mm. When installing, torque the spark plugs to 180 inch pounds.


To clean the engine, unbolt the air filter cover and engine cover. Use a dry rag or brush to wipe off the cooling fins, then reinstall the covers. To clean the oil cooler, wipe it down with a dry brush. Never use water to clean these components.

Need Something for Your Argo?

Shank’s Argo doesn’t just sell Argo ATVs and side-by-sides. We’re a full service dealer with a service department and a massive parts warehouse. If you need help fixing your amphibious ATV, visit our shop at 4900 Molly Pitcher Highway in Chambersburg, PA. Do you want to do the work yourself, and just need some parts? We ship across the United States and Canada. To order, visit us online at

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