Understanding Fuel Types for Time Attack Cars

Selecting the right fuel is a foundational decision for any Nashville Time Attack build. The fuel you pour into the tank directly affects cylinder pressures, ignition timing, and ultimately how much power your engine can safely make. In competitive environments like the Nashville Superspeedway or local circuit events, the difference between a podium finish and a mechanical failure often comes down to fuel quality and composition.

Octane Rating: The Critical Metric

Octane rating measures a fuel’s ability to resist knocking (uncontrolled detonation). Standard pump fuels in the United States range from 87 (regular) to 93 (premium). For modified engines with higher compression ratios or forced induction, 93 octane is the minimum safe starting point. However, many Time Attack cars running aggressive tuning or large turbochargers require 100 octane or more to avoid pre-ignition under heavy loads.

In Nashville’s summer heat, intake air temperatures can spike, increasing the likelihood of knock. A fuel with a higher octane rating provides a wider safety margin, allowing tuners to advance timing and boost pressure without risking engine damage. For naturally aspirated builds, 93 octane is often sufficient, but forced-induction cars benefit from stepping up to 100-octane unleaded race fuel or an ethanol blend.

E85 (85% ethanol, 15% gasoline) has gained traction in the Time Attack world due to its high effective octane rating (typically 100-105) and excellent cooling properties. Ethanol’s high latent heat of vaporization absorbs more heat from the intake charge, reducing the risk of knock and allowing higher power output. Many Nashville tuners recommend E85 for cars equipped with flex-fuel sensors and compatible fuel systems (stainless steel tanks, ethanol-rated lines, and upgraded injectors).

However, E85 does have downsides. Its lower energy density means fuel consumption increases by roughly 25-30% compared to gasoline. Additionally, ethanol can attract moisture and cause corrosion in fuel systems not designed for it. Racers running E85 must flush the system before long-term storage and use additives that stabilize ethanol fuel. Local availability of E85 is also a factor—while Nashville has several E85 stations, not all are consistent in ethanol content, which can vary seasonally.

Racing Fuels: Specialty Blends for Maximum Output

For dedicated Time Attack cars that never see street use, purpose-built racing fuels offer the highest octane ratings (often 110-118) and tightly controlled chemistry. Brands like VP Racing Fuels, Sunoco, and Torco provide leaded and unleaded options. Unleaded race fuels are preferable for modern engines with oxygen sensors and catalytic converters, though many race cars remove those emissions components.

Leaded fuels can lubricate valve seats and offer additional knock resistance, but they also contaminate spark plugs and oxygen sensors quickly. In Nashville’s track environment, where many events require mufflers and noise restrictions, running a leaded fuel may not be practical inside the sound limits. Most serious competitors opt for unleaded 100-octane or 104-octane race fuels when E85 is not an option.

Mixing Pump Fuel with Race Fuel

Some racers blend pump 93 with race fuel to achieve an intermediate octane level, such as 96 or 98. This can be cost-effective and allows fine-tuning. However, blending reduces the consistency of the fuel’s properties. If you choose to mix, always do so in the car’s tank and fill with the lower octane first, then add the higher octane, to get thorough mixing. A fuel sample can be tested with an octane meter for accuracy.

Fuel Additives: Boosting Performance and Reliability

Even with the perfect base fuel, additives can enhance performance, protect the fuel system, and ensure consistent operation over a race weekend. Not all additives are created equal—some are snake oil, while others deliver measurable benefits.

Octane Boosters: When and How to Use

Octane boosters are concentrated compounds that raise the effective octane of pump gasoline. Products like Torco Accelerator or VP Madditive can raise 93 octane to 100+ when added at the correct ratio. This is a convenient option for cars that cannot run E85 or race fuel but still need knock protection.

Most octane boosters contain MMT (methylcyclopentadienyl manganese tricarbonyl) or oxygenates. MMT can foul spark plugs and oxygen sensors if overused, so follow the manufacturer’s dosage carefully. For Time Attack cars that are driven to the track, an octane booster treatment before each event can provide the needed safety margin while allowing the car to run pump gas on the street.

Fuel System Cleaners: Maintaining Flow and Spray Patterns

Deposits on injector tips and intake valves disrupt fuel atomization, leading to power loss and uneven cylinder distribution. High-mileage engines benefit from a concentrated fuel system cleaner like Chevron Techron Concentrate Plus or Red Line SI-1 before a race day. Use these products about a tank before the event to clean the system, then refill with pure top-tier fuel.

For direct-injection engines, carbon buildup on intake valves is a chronic problem. Additives that reduce carbon deposits (like CRC GDI IVD Cleaner) can help, but mechanical cleaning (walnut blasting) periodically is still recommended. Nashville’s humidity and dust can also contribute to contamination—using a fuel filter and changing it before race day is a simple yet effective preventive measure.

Fuel Stabilizers: Storage and Between-Event Protection

Time Attack cars often sit for weeks between events. Ethanol blends degrade faster than pure gasoline, forming gum and varnish that clog fuel systems. Adding a stabilizer like Sta-Bil Storage or Sea Foam to the tank before storage prevents deterioration. If you run E85, use a dedicated ethanol stabilizer to prevent phase separation (the ethanol absorbing water and separating from gasoline).

For cars stored over winter, fill the tank to near-empty or full? Running a tank nearly empty invites condensation; a full tank with stabilizer minimizes air space and moisture. However, if the car sits for months, consider draining the fuel and running the engine dry to avoid stale fuel issues.

Corrosion Inhibitors and Lubricity Additives

Ethanol and some race fuels can be corrosive to certain metals. Additives containing corrosion inhibitors protect fuel rails, injectors, and lines. For high-pressure fuel pumps, lubricity additives (Opti-Lube XPD or Lucas Oil Fuel Treatment) reduce wear. This is especially important in cars running low-sulfur pump gasoline, which has less natural lubricity.

Choosing the Right Fuel and Additives for Nashville Track Conditions

Nashville’s climate and track configurations introduce specific variables. The Nashville Superspeedway is a 1.333-mile concrete oval with steep banking, but many Time Attack events take place on road courses like the Nashville Fairgrounds Speedway’s infield layout or transient events at the Music City Grand Prix circuit.

Altitudes and Ambient Temperatures

Nashville sits at roughly 600 feet above sea level. While not high-altitude, even modest altitude changes affect air density. On a 90°F summer day, the air is thin enough to reduce oxygen content, which can make knock more likely if the tune was done in cooler weather. Using a fuel with at least 100 octane or an octane booster becomes critical. Conversely, during cooler fall mornings, 93 octane may be perfectly adequate with a conservative tune.

Fuel Availability and Transport

Many Nashville racers pick up pump gas locally, but quality varies between stations. Seek out “Top Tier” gasoline retailers (Shell, Chevron, Exxon, etc.) that include more detergent additives. For race fuel, specialty shops like VP Racing Fuels Nashville or RPM Racing Fuels supply drums or jugs. Transporting race fuel requires proper containers (approved metal or plastic jerry cans) and ventilation in the vehicle—never store fuel jugs inside the passenger compartment.

Cost vs. Performance Trade-offs

Pump 93 octane costs around $4-$5 per gallon, while race fuel can be $8-$15 per gallon. E85 is often cheaper than premium, but you burn more of it. A typical Time Attack car consuming 10-15 gallons per event may see a cost difference of $50-$100 per weekend. For a competitive car, that’s negligible compared to tires and brake pads. However, if you are on a budget, a well-tuned car on 93 with a quality octane booster might be nearly as fast as a car on race fuel—but less consistent. Always prioritize engine safety first; it’s cheaper to buy better fuel than to rebuild a motor.

Fuel System Upgrades to Complement Fuel and Additives

Running high-octane race fuel or E85 often requires supporting modifications. If you plan to switch fuels regularly, consider a flex-fuel sensor that allows the ECU to adjust timing and fueling automatically. For E85, upgrade the fuel pump (Wally 450 or AEM 340 are popular), injectors (at least 1000cc for high horsepower), and lines (use stainless steel or PTFE to resist corrosion). A fuel pressure regulator and return-style system ensure consistent delivery under high demand.

Fuel additives should be added directly to the tank before filling, not mixed in small amounts. Shake or drive a few miles to allow thorough mixing. For octane boosters, follow the bottle ratios exactly—more is not better and can cause deposit buildup.

Final Recommendations for Nashville Time Attack Competitors

After evaluating the options, here is a practical strategy for Nashville Time Attack racers:

  1. For daily-driven street/track cars: Use 93 octane top-tier pump fuel with a splash of octane booster on race day. Run a fuel system cleaner every 5,000 miles.
  2. For dedicated track cars with flex fuel: Run E85 with a stabilizer added when the car sits more than two weeks. Flush the system with gasoline if storing over winter.
  3. For maximum power (forced induction, high compression): Use 100-104 unleaded race fuel. Add a fuel stabilizer if the fuel sits in the tank for more than a month.
  4. Always test your fuel choice by doing a few pulls on the dyno or a drag-strip run to confirm knock margin before a race.
  5. Monitor the weather and adjust fuel maps accordingly—or use an ECU that incorporates IAT compensation.

Consulting with local Nashville tuners such as those at Tennessee Speed Shop or The Racing Store can provide specifics for your setup. Proper fuel management will give you the edge needed in Nashville’s competitive Time Attack scene, helping you turn laps that are both fast and reliable.

External Resources for Further Reading