dejanh

I recently purchased a used, albeit like new, 2017 Lexus IS 300 F Sport II AWD. It had approximately 9,500km (~5,900 miles) on it when I bought it a few days ago. I have been driving since then in standard mode, fairly gingerly mind you (no heavy foot on gas, etc.) and yet I am getting atrocious fuel economy from the car so far. My current fuel burn rate is approximately 19.5L/100km (~12.1mpg) when driving. I drive almost exclusively in the city (95%+ of the time is in-city), commuting to/from work and around the city. Yes, the city driving is congested, there are lots of traffic lights, and my commute to work I am going up hill/down hill all the time with an average speed only about 18km/h (~11mph). Despite that the numbers that I am getting are so far from the rated 12.9L/100km that I simply don't know what to think of it. It makes me feel like the car is broken somehow.

For reference, before this I had a 2005 Acura TL with a 3.2L V6 FWD and it burned about 15L/100km driving in the same conditions, but the car was also 13 years old with 130,000km on it (~81,000 miles). My A/C is on, but so it was also in the TL I drove before this car. All in all, I am simply shocked at the fuel consumption right now and am looking for ideas on what could be the possible culprits that are resulting in this. I already eliminated tire pressure as a factor as everything is properly inflated to 36 psi cold. I do not intend to drive the car in ECO mode as I know it was not rated 12.9L/100km in ECO mode so I am expecting to get close to that for in-city driving in normal mode. Could it seriously be that my driving conditions are this bad and that the car is so much less efficient than my TL that it actually burns 27% more fuel?

truu

12.9L/100km sounds about right to me. I was getting high 11s and low 12s during the summer. Now I'm getting around 13s during the winter here in Winnipeg. I am sure others would agree.

Pittsy

I know your against eco mode, but if its suffering that much it has to be worth a shot.

BlazeL

2018 IS300 here. How soon after you fill up gas are you checking it? I do a mostly highway driving but the gas station where I fill up is in the city and I've always noticed how bad my gas mileage is for the first 10 miles or so.. Around 10-15 mpg because its just me sitting in traffic or at stop lights. So yeah I can definitely see how that could be possible. I typically drive around 80 mph to work for 25 miles and I average about 21 mpg on a tank. More or less off topic but what I've gathered from simply watching the mpg rate is that the optimal speed for fuel consumption is somewhere in the 40-55 mph range. Probably designed that way.

dejanh

truu

Yes sorry I did.

Did you reset the fuel economy before noticing that? The data sample size is small and combined with the traffic jam, it will lead to the bad fuel economy. That's just one possibility.

If you really want to find out the fuel economy. Track how much km you get on a full tank rather than the rate calculated by the car.

arentz07

I've heard using Snow mode also helps. I haven't really had a need for it - in the winter I still manage about 18 MPG. Keep in mind, I don't really experience any traffic on my commute.

E46CT

As said don't speak anything of anything until you average out (actual calculated) mileage per tank. And take it a step further. Still don't say anything until you do this 3x. Then average out the #s from the three results.

If you reset your mileage then make one stop and go commute to work, you can easily get 12mpg. i'll get 12-14 mpg on my way home/or to work in traffic sometimes but it's bumper to bumper. but overall about 19 mpg. which is still sucky. but reality.

dejanh

I did reset the fuel economy and am only looking at how the car is performing since the last fuel-up. I was going to do exactly what you suggest above though and average out the total distance traveled vs. fuel consumed based on a full tank.
I thought about this as well. It's interesting because it would force the car to start in 2nd gear and may not rev up as much in the stop-and-go traffic all the time. I'd rather not have to hack my way around fuel consumption but this tip is definitely on my mind.
Yeah, that's what I am seeing basically. The traffic itself is not necessarily bumper to bumper always, but I rarely get more than 100m stretch of free road to drive before I either hit traffic or a traffic light. I am intending to ultimately try driving in normal, ECO, and sport mode to see how each behaves after a fill-up. Because my routes are generally always the same each would be technically subject to the same test. Right now I'm basically sitting at around 12-12.5mpg at best. I will have to burn through a few tanks it seems before I can really say how well it does. I'll post back with results, eventually, as this will take at best a few weeks to complete.

Thank you all for the feedback so far!

VisualEcho

I have a 2018 350 F Sport and I feel the same way, the car literally drinks gas...and I'm being super easy on it because I still believe in break-in periods. I came from a 2007 Acura 3.2 TL which got 30% better gas mileage in the SAME conditions.

This car has some fantastic attributes, but it's hard on gas and on tires...EVEN if you don't drive the car hard.

dejanh

Thanks for the feedback. We effectively came off of the same car since the 2005 and 2007 TL are basically identical. I'm glad I'm not the only one that feels that the car gulps down gas. I wasn't expecting much considering that I bought a performance car, but I'm so far off of the rating that it just boggles my mind. I am going to see where I settle after some driving as indicated before but either way I feel I'm in for 20%-30% higher gas bills. Quite disappointed about that since the fuel rating for this car is supposed to be 12.9L/100km in city which scaled to the new rating system is the same as the TL. In practice it's not even close.

VisualEcho

I wouldn't go that far. The IS is a compact luxury car, not really a performance car. I guess what I'm saying is, anything sporty on the car took a back-seat to longevity/reliability. It's really not that heavy, to be honest, and the engine isn't that big either, so I'm a little lost on why the gas mileage is so bad, but it is what it is.

dejanh

I do agree to an extent. It is powered by a 3.5L V6 and on top of that it is AWD. There is a decent amount of power behind it (albeit more could be had if the additional HP was unlocked via the ECU flash). What I am surprised at is that the car is quite literally 12 and 10 years newer than either of our prior cars with only a 0.3L larger engine and an additional 70kg in weight yet the gas consumption is so much worse. I'm still optimistic I may see some improvement. If I can bring it down to the level of the TL I will accept that. I'm still ways away from it though.

arentz07

The transmission and engine are pretty much 13 years old by now, however. The 2GR-FSE engine was first used in an IS back in 2005 (model year 2006), and the A760H transmission debuted around the same time for the GS 300 AWD. The main difference between the second and third gens is the final drive ratio, which has been made less aggressive in the third generation.

Considering the older drivetrain and higher curb weight compared to the last generation IS, it could be worse I suppose.

dejanh

This was something I had in the back of my mind as well. Thank you for pointing it out.