Significant difference in IS350 fuel economy between 60 and 70 MPH
06-09-08, 12:39 PM
#20
It would be interesting to see how much difference in fuel economy could be made by turning the A/C on full max versus "just barely survivable". Turning the A/C completely off would be suicide with the windows up. I doubt there would be more than 1 MPG difference.
06-09-08, 02:45 PM
#21
Joe, your point about the A/C got me thinking. I don't have any idea how many BTUs / hour it takes to cool my interior to 74 degrees F on a 95 degree day, but I would be surprised if it was anywhere close to 10,000 BTUs / hour. For comparison sake, a 10,000 BTU/hour window unit A/C from sears requires 900 watts of electricity. A gasoline generator that would provide that 900 watts (Honda) requires about 0.15 gallons per hour with continuous cooling. This would be about 3 MPG reduction (at 60 MPH) if the A/C in our Lexus is as inefficient as this 10K window unit powered by a carbureted generator. I would like to think that our A/C requires far less fuel than that.
Last edited by Gernby; 06-09-08 at 03:44 PM.
06-09-08, 03:48 PM
#22
Driver School Candidate
Join Date: May 2008
Location: California
Posts: 35
Likes: 0
Received 0 Likes
on
0 Posts
Confirmed on IS 250
I just noticed the same on my IS 250 AWD last night, albeit on short 5-mile portions:
- cruise control set to 74mph - avg MPG 26.9
- cruise control set to 70mph - avg MPG 28.3
- cruise control set to 65mph - avg MPG 32.1
Last edited by vlexus; 06-09-08 at 03:52 PM.
06-09-08, 04:53 PM
#24
Lead Lap
iTrader: (8)
Join Date: Jan 2007
Location: CA
Posts: 734
Likes: 0
Received 0 Likes
on
0 Posts
Attachment 125318 way better than 35 mpg this is before the traffic at nevada state line.
And the biggest affect on mileage is the driver, cruising speed and accel/decel is the biggest impact.
06-09-08, 05:29 PM
#25
Tech Info Resource
iTrader: (2)
Now that I think about it some more, this could have been influenced by wind speed / direction. I've done this test many times at 60 MPH, and I usually get about 36 MPG on the way to the boat, and 35 on the way back from the boat ~6 hours later. I've never really considered wind as a factor since the results are so repeatable. However, yesterday was particularly windy on the lake, and I would guess that I was heading right into it when I did the 70 MPH test.
So I don't get worked up over single run data anymore.
It is truly a remarkable time in US history. We've bought cars making more than 300 hp, and we're fussing over fuel economy.
06-09-08, 06:14 PM
#26
Lead Lap
Join Date: Dec 2005
Location: Fl
Posts: 560
Likes: 0
Received 0 Likes
on
0 Posts
I'm sure your self tuner is also helping right.
06-09-08, 06:57 PM
#27
I will definitely repeat this test over the next few weeks to see if the results are the same. I just wish it would be possible to use the cruise control through downtown Dallas...
BTW, my piggy-back ECU has absolutely no impact on anything at partial throttle.
BTW, my piggy-back ECU has absolutely no impact on anything at partial throttle.
06-09-08, 07:10 PM
#28
Lexus Champion
Last month I was in west Texas on I-10 where the speed limit is 80 mph. Over a 100 mile stretch on cruise, with no use of brakes the whole time and with terrain fairly flat with some rolling hills I saw 25.2 mpg.
06-09-08, 07:23 PM
#29
Lead Lap
Join Date: Dec 2005
Location: Fl
Posts: 560
Likes: 0
Received 0 Likes
on
0 Posts
