dman51

So far I've been enjoying my new is300 but I'm somewhat concerned with the real world MPG's that I've been seeing. I'm hovering around 17-18 in daily driving which is brief highway with light traffic and back roads. I drive in ECO full time and combined this car should be getting 21. I took a long highway drive in no traffic and with ECO/Cruise control managed to get my avg. up to around 20.5 but sticker says 26 highway. This is only on my second full fill up and my dealer told me that after 3 full fill-ups it should start to be more accurate. Any truth to this? Is this a break in period or are these numbers those have experienced?

redraptor

Sounds about right since the 300 and 350 get the same mpg even with the HP difference.

It might get better after 1000 miles or so but don't expect a major difference. Warmer temps will help as it takes less time for the engine to reach optimal temperature.

I once drove from NJ to PA, all highway in ECO mode and was able to get 29 mpg on my previous 2014 IS350.

goldengame

With my 2015 IS350 AWD, I get about 23 mpg with 65/35 highway/city in the summer. Seems like it's about 1 mpg less with my winter tires. I'd expect the IS300 to get around the same mileage.

tunertony

I also have a 16 IS300. I averaged 18mpg the first tank with 80% highway driving, the second tank was 20mpg with 80% highway and the third tank is now averaging about 22mpg.

dman51

29 is impressive and what I'd like to achieve on a drive like that.

That's what I'm hoping to get to but so far the first two tanks have been well below that and I'd expect the 300 to at least be on par with your 350 AWD even if not any better.

Glad to hear my dealers comment had some truth to it, I'm hoping for better results come the third tank as you experienced.

Thanks for all the replies.

evident

trade it in and get the 350, at least you'll get performance w/ the same MPGs

tunertony

All I need is a piggy back ecu or tune and i have an IS350.

silvaIS

iTrader: (2)

when trying to achieve performance you will be getting 10 mpg or less

SlickRSM

I'm in the same boat, I have a 2015 250 AWD F-sport gets about 17-18 in similar driving conditions. Before that had an 2007 250 AWD that was slightly better in the same conditions.

Suspenders

That seems to be what I'm getting as well... 18 MPG. Mixed city & highway... 90% city though.

evident

Don't kid yourself.

IScrazzd

On my first tank still, and so far am getting 17/18 mpg.

goldengame

If you guys care, I decided to drive gently (like a normal person lol) for a 100 km trip on the highway. I ended up getting 7L/100km (33.6 mpg) with my 2015 IS350 F-Sport AWD.

drewba

The IS 300 has been out for almost a complete model year now. How are people's MPG experiences now that the engines are broken in?

Thanks