We recently got the opportunity to run the all-new 2021 Lexus IS sports sedan on our real-world highway fuel economy test. This was an all-wheel-drive Lexus IS 350 F Sport model, meaning it comes with Lexus’s carryover 3.5-liter V-6 engine making 311 horsepower. Unlike the rear-wheel-drive IS 350, which gets an 8-speed automatic transmission, the AWD model makes do with only 6 forward gears.
The transmission didn’t seem to have too big of an effect on highway fuel economy, however, as the top-trim Lexus IS still managed 29 MPG in our testing. The IS’s onboard MPG calculation was 30 MPG, helping to confirm this figure. EPA fuel-economy estimates have not yet been released for the 2021 IS.
The 2021 Lexus IS 350 AWD sports a 17.4-gallon fuel tank. Therefore, at 29 MPG, one could expect to travel just over 500 miles before running out of a full tank. And with the comfortable seats, quiet cabin, and impressive Mark Levinson audio system, 500 miles should be no problem.
Daily Motor’s real-world highway-fuel-economy test consists of over 100 miles of consistent highway driving. We fill the car using the “three-click method,” meaning running the gas pump on high flow until it clicks, waiting 10 seconds, running low flow until it clicks again, waiting another 10 seconds, then running low flow one last time. The lowest-octane fuel accepted by the vehicle’s manufacturer is used. We then drive 54.2 miles on public highway in one direction and then back in the opposite direction, attempting not to draft or drive aggressively. We set the cruise control at GPS-indicated 73 MPH in an attempt to achieve a moving average speed of 70 MPH over the entire test. Upon return to the gas station, we refill at the same gas pump as the initial fill using the same method. Miles per gallon is determined by dividing total miles traveled by fuel used. In cases where our observed figure differs greatly from the vehicle’s indicated figure and/or EPA’s estimate, we may recommend a number in between or plan to retest the vehicle.