What Gas Does Infiniti G37 Take

So, you're an Infiniti G37 owner, which means you appreciate a blend of luxury and performance. And like any performance-oriented vehicle, understanding its fuel requirements is crucial. The question we're tackling today is: What type of gas does your G37 *actually* need? While it might seem straightforward, there's more nuance than just looking at the gas cap. This article will delve into the specifics, acting as your definitive guide to your G37's fuel needs.

Purpose

Why bother knowing the exact fuel requirements? Several reasons: First and foremost, using the incorrect fuel can negatively impact performance and even damage your engine over time. Second, understanding fuel grades allows you to make informed decisions about your fuel purchases, optimizing for performance and budget. Finally, if you're diagnosing performance issues, the fuel type is one factor you need to eliminate as a potential cause.

Key Specs and Main Parts

Let's start with the basics. The Infiniti G37, produced from 2008 to 2013, primarily came equipped with one engine: the VQ37VHR. This is a 3.7-liter, naturally aspirated (meaning it doesn't have a turbocharger or supercharger) V6 engine. The key specifications influencing fuel requirements are:

Compression Ratio: The VQ37VHR boasts a compression ratio of 10.5:1. This is a moderately high compression ratio, meaning the air-fuel mixture is compressed significantly within the cylinders before ignition. High compression ratios often necessitate higher octane fuels.
Variable Valve Timing (VVEL): VVEL, or Variable Valve Event and Lift, is Nissan's advanced variable valve timing system. It allows for precise control over valve opening and closing, optimizing engine performance and efficiency across the RPM range. This system is sensitive to fuel quality; lower-quality fuel can lead to carbon deposits affecting the VVEL system over time.
Knock Sensors: The engine is equipped with knock sensors. These sensors detect engine knock or detonation, a phenomenon where the air-fuel mixture ignites prematurely and uncontrollably. The engine control unit (ECU) uses these sensors to adjust timing and prevent damage. However, relying solely on knock sensors isn't a long-term solution for running lower octane fuel.

Fuel System Components:

Fuel Tank: Holds the gasoline. Capacity varies slightly depending on the coupe or sedan model.
Fuel Pump: Located in the fuel tank, it pumps fuel to the engine.
Fuel Filter: Filters out impurities from the fuel.
Fuel Rail: Distributes fuel to the injectors.
Fuel Injectors: Spray fuel into the intake ports or directly into the cylinders (port injection in the G37).
ECU (Engine Control Unit): Manages the entire fuel injection system based on sensor data.

Fuel Recommendations and Octane Rating

Infiniti recommends using premium unleaded gasoline with an octane rating of 91 or higher in the G37. This recommendation is based on the engine's design and the need to prevent engine knock. But what does "octane rating" actually mean? The octane rating measures a fuel's resistance to detonation or knocking. Higher octane fuels are more resistant to pre-ignition.

Here's the breakdown:

Regular Unleaded (87 Octane): Typically the cheapest gasoline option. Not recommended for the G37.
Mid-Grade Unleaded (89 Octane): May be tempting as a compromise, but still not ideal for long-term use.
Premium Unleaded (91-93 Octane): This is what Infiniti recommends and is generally the best choice for your G37.

Can you use lower octane fuel? Technically, yes. The engine's knock sensors and ECU will attempt to compensate by retarding the timing. However, this results in reduced performance (less horsepower and torque), decreased fuel economy, and potentially increased engine wear over time. Constantly running on lower octane fuel puts undue stress on the engine and can lead to issues like carbon buildup. Using premium fuel ensures optimal performance and engine longevity.

How It Works

The G37's fuel system is a closed-loop system managed by the ECU. Here's a simplified overview:

The fuel pump draws fuel from the fuel tank and sends it through the fuel filter.
The filtered fuel travels to the fuel rail, which distributes it to the fuel injectors.
The ECU determines the amount of fuel to inject based on various sensor inputs, including engine speed (RPM), throttle position, air flow, and oxygen sensor readings.
The fuel injectors spray the precisely metered fuel into the intake ports.
The fuel mixes with air, and the mixture is drawn into the cylinders.
The spark plugs ignite the mixture, causing combustion and powering the engine.
The exhaust gases are expelled, and the oxygen sensors monitor the exhaust to ensure the air-fuel ratio is correct (14.7:1 is stoichiometric, the ideal air-fuel ratio for complete combustion).
The ECU uses the oxygen sensor data to make adjustments to the fuel injection system, continuously optimizing performance and efficiency.

When you use a lower octane fuel, the combustion process becomes less stable. The ECU detects knock and retards the timing, delaying the spark. This reduces the peak cylinder pressure and temperature, preventing further knock. However, it also makes the combustion less efficient, resulting in a power loss.

Real-World Use – Basic Troubleshooting Tips

Here are some signs that your G37 might be experiencing fuel-related issues:

Poor Acceleration: A noticeable lack of power, especially during acceleration.
Reduced Fuel Economy: Burning through fuel faster than usual.
Engine Knocking or Pinging: A metallic rattling sound, particularly under load.
Rough Idle: The engine vibrates excessively at idle.
Check Engine Light: Illuminated on the dashboard. Codes related to fuel trim, misfires, or knock sensor activity could indicate a fuel issue.

Troubleshooting steps:

Verify Fuel Type: Ensure you're using the correct octane fuel.
Check for Fuel Leaks: Inspect the fuel lines, fuel rail, and fuel injectors for any signs of leaks.
Fuel Filter Replacement: A clogged fuel filter can restrict fuel flow. Replace it according to the manufacturer's recommendations.
Fuel Injector Cleaning: Dirty fuel injectors can affect fuel atomization and spray patterns. Consider using a fuel injector cleaner or having them professionally cleaned.
Check Fuel Pump Pressure: A weak fuel pump can't deliver enough fuel to the engine. Use a fuel pressure gauge to check the pressure.
Scan for Trouble Codes: Use an OBD-II scanner to check for any trouble codes related to the fuel system.

Safety

Working with fuel systems involves inherent risks. Gasoline is highly flammable, and fuel vapor is explosive.

Always disconnect the negative battery terminal before working on the fuel system.
Work in a well-ventilated area to avoid inhaling fuel vapors.
Avoid sparks or open flames near the fuel system.
Use appropriate safety gear, including eye protection and gloves.
Properly dispose of any fuel-soaked rags or materials in a sealed container.
Fuel Injectors are high pressure components! Never attempt to disassemble a fuel injector while the fuel system is pressurized. Depressurize the system by disconnecting the fuel pump relay and running the engine until it stalls.

While this article provides a comprehensive overview of the G37's fuel requirements, consulting the vehicle's owner's manual and a qualified mechanic is always recommended for specific diagnoses and repairs.

We have a detailed diagram of the G37's fuel system available for download. This diagram provides a visual representation of all the components and their relationships, which can be invaluable for troubleshooting and repairs. Feel free to reach out to obtain it.