Types Of Gas A Lexus IS 250/300/350/500 Takes (Explained)

On this blog, we do a lot of research regarding specific questions about different cars. Today we’ll look at the Lexus IS and answer what kind of gas this car requires. To find the answer, we’ve reviewed the owners’ manuals of the IS 250, 300, 350, and 500. Here’s a quick answer:

Lexus IS 250 manufactured between 2006 – 2015 take premium, unleaded gasoline with an octane rating of 91 or higher.
All model years of the Lexus IS 300 (2001 – 2005, 2016 – present) take premium, unleaded gasoline with an octane rating of 91 or higher.
All model years of the Lexus IS 350 manufactured from 2006 onwards take premium, unleaded gasoline with an octane rating of 91 or higher.

However, that doesn’t tell the whole story. Below we’ll dive into the details of what kind of gas this crossover takes. We’ll talk about reformulated gasoline, E-85, and gasoline with additives. Should or shouldn’t you use this for the Lexus IS? We’ll also talk about each generation’s fuel mileage, possible knocking noises, and much more. Read on!

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Infographic on the fuel types for a Lexus IS.

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Does The Lexus IS Need Premium Gasoline?

As you have been able to read in the introduction, all generations and all variations of the Lexus IS require premium gasoline with a minimum octane rating of 91. This is different than the Lexus RX350 which uses premium gas for the earlier generations and 87 octane fuel for later generations.

We´re well aware that 91-octane is more expensive than regular gasoline (87 octane), and that´s why many people wonder if they can´t use that instead.

However, this is not a smart thing to do. 91-octane is specifically recommended, and Lexus even states in the owners´ manuals that using gasoline with a lower octane rating will result in problems that aren´t covered by warranty if things go wrong. Therefore, use 91 octane gasoline at all times.

Also read: How Many Miles Can A Lexus IS 350 Last? (+Reliability Scores)

What Types Of Gasoline Can And Can’t Be Used?

Furthermore, it’s essential to talk about the different kinds of gasoline and additives available on the market and whether or not these should be used in your model of the IS.

Reformulated Gasoline

Another important part we need to discuss is whether or not Lexus IS models are suitable for reformulated gasoline and whether this type of gasoline is preferred.

Reformulated gasoline is the gasoline that’s designed to burn cleaner and is, therefore, better for the environment compared to non-reformulated gasoline. In some parts of the United States, reformulated gasoline is mandatory, and there’s not even any other gasoline you can access.

Therefore, it’s good to know that Lexus IS, like most cars in the United States, is compatible with reformulated gasoline. Furthermore, Lexus advises using reformulated gasoline whenever available because it doesn’t diminish the performance or lifespan of the car while providing cleaner emissions.

Gasoline/Oxygenated Blends Or E-85

Another form of gasoline we need to discuss is the use of so-called oxygenated blends of gasoline. These are types of gasoline that contain a certain percentage of ethanol. Ethanol is a biofuel mixed into many types of gasoline in the United States because it provides cleaner emissions than non-oxygenated gasoline.

Lexus IS 250 manufactured between 2006 – 2014 can take a maximum of 10% ethanol (E10), whereas the ones made in 2015 can take 15% ethanol (both E10 and E15).
Lexus IS 300 manufactured between 2001 – 2005 can take a maximum of 10% ethanol (E10), whereas the ones made from 2016 onwards can take 15% ethanol (both E10 and E15).
Lexus IS 350 manufactured between 2005 – 2013 can take a maximum of 10% ethanol (E10), whereas the ones manufactured from 2014 onwards can take a maximum of 15% ethanol (E15).

Furthermore, it’s good to know that gasoline can also contain methanol, and this is another type of oxygenated blend. However, Lexus strictly advises against using methanol in any form since this will undoubtedly damage the fuel system.

Gasoline With Added Materials

Many people wonder if adding materials to your fuel can be beneficial. This is a very standard question to have, given that there are many products on the market that are supposed to either improve the performance of your vehicle (octane boosters) or its durability (deposit cleaners).

However, let it be clear that adding additives to your gasoline is strongly advised against by Lexus and all other carmakers. This is because some of these additives will contain silicon or forms of metal that won’t ‘help clean your engine’ but will damage your car’s fuel system.

Instead, it’s advised that you buy gasoline that already has all the proper additives mixed into it. This type of fuel is typically referred to as TOP TIER. Gasoline from TOP TIER retailers has more than the minimum amount of additives mixed into it.

Furthermore, these retailers are regulated by their organization, and research has shown that the engine does stay cleaner (and therefore performs better) when using fuel from these retailers. You can find a retailer in your area via toptiergas.com.

What If I Hear A Knocking Noise From The Engine After Refilling?

There are multiple reasons why an IS can produce a knocking noise. However, if your car develops a knocking noise right after refueling, this most likely indicates a problem with the gasoline you’ve used.

First, let it be clear that a slight knocking noise is never a significant problem. Especially when driving uphill or when towing can, cars develop a faint knocking noise.

However, if you hear a loud knocking noise, and if it happens right after refueling, you’ve most likely used gasoline with a lower than recommended octane rating. If you hear a knocking noise right after refueling, you must stop the car immediately and call your garage or dealer.

Assuming you did fill up with the wrong kind of gasoline, your car will need to be towed to the garage, drained of its fuel, and the fuel filter will also need to be replaced.

Also read: 16 Common Problems Of A Lexus IS 350

Does the Lexus IS Have Good Gas Mileage?

It’s also important to know the car’s fuel economy you have and/or want. Below, we outlined the four different models of the IS we’ve discussed so far and divided them up for each available generation.

Lexus IS 250

In its production span between 2006 – 2015, the IS 250 had only one engine configuration with the following MPGs:

Engine	Combined MPG	City MPG	Highway MPG
2.5L	24	21	29

Lexus IS 300

The Lexus IS 300 used two completely different engines in the two separate generations that have been made.

Engine	Combined MPG	City MPG	Highway MPG
3.0L (´01-´05)	18	16	23
2.0L (´16 – present)	25	21	31

Lexus IS 350

The Lexus IS350 largely used the same engine throughout its generations. The fuel economy these days is only marginally better than the one introduced in 2006.

Engine	Combined MPG	City MPG	Highway MPG
3.5L (´06-´13)	21	19	26
3.5L (´14 – present)	23	20	28

Lexus IS 500

The IS 500 uses a large 5.0L V8 engine focused mainly on performance instead of fuel economy.

Engine	Combined MPG	City MPG	Highway MPG
5.0L	20	17	25

What’s The Gas Tank Size Of A Lexus IS?

Lexus IS 250 made between 2006 – 2013 have a fuel tank capacity of 17.2 gallons or 65 liters. The ones made between 2014 – 2015 have a fuel tank capacity of 17.5 gallons or 66.5 liters.
All model years of the Lexus IS 300 (2001 – 2005, 2016 – present) have a fuel tank capacity of 17.5 gallons or 66.5 liters.
Lexus IS 350 made between 2006 – 2013 have a fuel tank capacity of 17.2 gallons or 65 liters, whereas the ones made from 2014 onwards have a fuel tank capacity of 17.5 gallons or 66.5 liters.

Sources

Stefan K.

Hi! My name is Stefan; I’m the owner and lead writer at TheDriverAdviser.com.

I’m an active writer on this blog myself, as well as a novice car mechanic. For the really technical stuff, I find writers with experience as a mechanic or who have studied mechanical engineering.

Read more about our fantastic team on our about page!

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