What gas does a 1998 Lexus LS400 take?
The 1998 Lexus LS400 requires premium unleaded gasoline with an octane rating of 91 or higher. In the United States this typically equates to 91 AKI or higher, and ethanol blends such as E10 are generally acceptable.
Understanding the LS400's fuel requirements is essential for maintaining performance and longevity. This article outlines the official octane guidance, regional variations, and practical fueling tips for owners of this late-1990s luxury sedan.
Fuel requirements for the LS400
The following details reflect typical recommendations from Lexus/Toyota for the LS400 model and are applicable to most US-market examples of the era.
- Fuel type: Premium unleaded gasoline
- Minimum octane: 91 AKI (approximately 91 RON in many markets)
- Ethanol compatibility: Generally compatible with up to 10% ethanol (E10) where allowed by local fuel standards
- Avoid fuels with high ethanol content beyond 10% or non-premium grades
Using the correct octane and fuel type helps prevent engine knock and preserves performance and longevity.
Regional considerations and tips
Fuel standards and octane labeling differ by region. Below are the typical expectations for North America and Europe, with a reminder to consult the owner’s manual for your specific market.
United States and Canada
Recommended: Premium unleaded gasoline, 91 AKI or higher. E10 blends are common and acceptable; avoid regular 87 octane. Always follow the fuel label and door sticker for the exact grade recommended by your vehicle.
Europe and other markets
Recommended: Premium gasoline with 95 RON or higher. In many countries, 95 RON is the baseline for premium, with 98 RON available as a higher-grade option. Check your local fuel specifications and the owner's manual for precise guidance.
Note: Do not use leaded gasoline. Ethanol content and compatibility may vary; always ensure fuel meets the premium rating specified by Lexus for smooth operation of the 1UZ-FE engine.
Summary
The 1998 Lexus LS400 runs on premium unleaded gasoline with a minimum octane rating of 91 AKI in the US (roughly 91 RON in many regions), and is generally compatible with E10 ethanol blends where permitted. Regional octane standards vary, so always consult the owner's manual or a Lexus dealer for the exact specification in your country. Using the recommended fuel ensures optimal performance and longevity of the 1UZ-FE engine.
Does Lexus take 91 or 93 gas?
With that said, you're probably asking yourself, “Does Lexus require premium gas?” For most (but not all) of the Lexus lineup, the answer to that question is yes. Most Lexus models require you use at least 91 octane (premium) gasoline, while there are a few that can use 87 octane regular unleaded.
What kind of gas does a Lexus LS400 take?
Although Lexus suggests using higher octane fuel above 91 for this vehicle, using regular fuel or 87 octane should not cause it to stop running like this. The only consequence of using regular gas would be a minor loss of performance.
How much is a 1998 Lexus LS400 worth today?
The value of a used 1998 Lexus LS 400 ranges from $1,261 to $3,976, based on vehicle condition, mileage, and options. Get a free appraisal here.
What happens if I put 87 instead of 91?
If you put 87 octane instead of 91 in a car that requires it, your modern engine's computer will likely adjust timing to prevent damage, but you may experience reduced performance and fuel efficiency. For a one-time mistake, drive gently and fill up with 91 octane the next time to dilute the fuel. However, consistently using lower-octane fuel in a high-compression or performance engine can lead to engine knocking and potential damage.
What to expect in the short term
- Reduced performance: You may notice less acceleration and overall power.
- Engine knocking or pinging: This is a rattling noise that can occur when the fuel pre-ignites in the cylinder.
- Decreased fuel economy: Your car may use more fuel to go the same distance.
How to mitigate the effects
- Avoid hard acceleration: Drive gently, especially at high speeds or when climbing hills, to minimize the risk of engine knocking.
- Fill up with 91 octane: When your fuel tank is low, fill it up with 91 octane to mix with the remaining 87 octane fuel. This will dilute the lower-octane fuel and raise the overall rating.
- Check your owner's manual: The manual will specify if 91 octane is a requirement or simply a recommendation.
- Be cautious with performance vehicles: Cars with turbochargers or high-compression engines are more susceptible to damage from lower-octane fuel, so it is especially important to avoid aggressive driving.
