Does The Lexus GX 550 Require Premium Gas & What Is The SUV's Expected MPG?

Lexus made some significant changes when it redesigned the GX SUV for the 2024 model year. Gone was the Lexus GX 460 model, which was beginning to feel its age along with its 301-hp, 4.6-liter naturally aspirated V8 engine. In their place, the Japanese luxury carmaker offered buyers the third-generation GX 550 with a new 3.4-liter twin-turbocharged V6 that produces 349 horsepower and 479 lb-ft of torque. Changes were also made to the transmission, with a quicker-shifting 10-speed automatic replacing the previous six-speed auto.

There's still some continuity, however. Like the GX 460, the Lexus GX 550 requires premium gas with an octane level of 91 or higher. Using high-octane gasoline helps reduce the possibility of spontaneous combustion and potentially harmful engine knock. Using the recommended grade of fuel also helps deliver optimal fuel economy. According to EPA estimates, buyers can expect the 2024 Lexus GX 550 to deliver 15 mpg city, 21 mpg highway, and 17 mpg combined. That average is a little higher than the second-generation GX 460, which delivers an EPA-estimated 15 mpg city, 19 highway, and 16 combined. The quoted Lexus GX 550 mpg applies to all six trims: Premium, Premium+, Luxury, Luxury+, Overtrail, and Overtrail+.

Like with any car, the fuel efficiency of a Lexus GX 550 depends on more than just fuel type.According to the EPA, aggressive driving habits such as hard braking, speeding, rapid acceleration, and switching lanes quickly — which can increase friction when steering left or right — tend to reduce fuel economy by between 15 and 30% at highway speeds and 10-40% in stop-and-go driving.

As well, making frequent short trips, driving on unpaved surfaces, driving up and down hills, and running the air conditioner (especially at the highest setting) can all contribute to lowering your Lexus GX 550's overall fuel economy. Cars also tend to be less fuel-efficient when you ignore preventative maintenance, like regular changes of oil and spark plugs. You'll also want to make sure you keep up with recommended maintenance for transmission, transfer case, and differential fluid. Low tire pressure can worsen fuel economy as well.

Some of the factors above explain why real-world fuel economy is often different from official EPA figures, which are determined in the lab. For instance, drivers of the current-generation GX 550 have reported fuel economy estimates that are slightly higher or lower than the EPA's rating. One owner of a GX 550 Overtrail+ posted to the r/Lexus GX subreddit reporting 14.9 mpg in city driving and 22.3 mpg on the highway. While the city return accurately reflects the EPA's estimate, the highway figure is 1.3 mpg higher than the EPA's 21 mpg rating.

In their comment, u/stravosuser said they averaged 13.7 mpg in combined driving, the majority of which was done in the city. Another owner, u/n541x, recorded between 13.4-14.5 mpg in the city, 21 mpg at speeds between 65 and 75 mph, 18 mpg at 85 mph, 24 mpg at 55 mph, and an astounding 28 mpg at 45 mph. This underscores the fact that speed is a determining factor in the GX 550's fuel economy. If you're happy with the Lexus GX's fuel economy and presently have it on your radar, we've rounded up other things you should know before buying the midsize luxury SUV.