MPG averaging at 65 mph vs 85 mph highway cruising IS 250
04-26-21 | 08:02 AM
#1
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Racer
Joined: Sep 2017
Posts: 1,667
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From: nj
MPG averaging at 65 mph vs 85 mph highway cruising IS 250
I see a lot of questions on mpg in this car and some people say it's not that good, I was surprised today though. Driving down I-95 NJ turnpike with decent varying slopes (up and down) did 2 tests speeds on cruise
Distance for both was about 2-3 miles
Tire pressure in all tires heated up: 38 PSI
Weight modifications:
resonator / muffler cut out (reduced)
aftermarket shallow sub & amp combo (increased)
wheel spacers (increased)
No passengers / items in the car
85mph - 25 mpg average - tach was at around 2800-2900 rpm
66mph - 32 mpg average - tach was at around 2200-2300 rpm
I feel like if I did 55-60mph which would set the RPM below 2000, it would be even better. Pretty insane IMO. The way I drive normally (which is pretty rough) I was getting 20 mpg combined.
Distance for both was about 2-3 miles
Tire pressure in all tires heated up: 38 PSI
Weight modifications:
resonator / muffler cut out (reduced)
aftermarket shallow sub & amp combo (increased)
wheel spacers (increased)
No passengers / items in the car
85mph - 25 mpg average - tach was at around 2800-2900 rpm
66mph - 32 mpg average - tach was at around 2200-2300 rpm
I feel like if I did 55-60mph which would set the RPM below 2000, it would be even better. Pretty insane IMO. The way I drive normally (which is pretty rough) I was getting 20 mpg combined.
04-26-21 | 10:08 AM
#2
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Joined: Nov 2016
Posts: 8,714
Likes: 4,012
From: GA
Wind resistance makes a significant difference no matter what vehicle we're talking about.
Here's what the government has to say about our cars: https://www.fueleconomy.gov/feg/driv...0to%2075%20mph).
I believe drag is proportional to the square of speed. So as you could imagine, good fuel economy comes from a balance of getting the engine in its most efficient RPM range and keeping the aerodynamic drag in check.
When I was driving the GLI down from MO to GA, on my first day, I was going 80-85 MPH and got about 36 MPG average. The next day, I would say I was going about 75-80 MPH instead, and averaged 38 MPG. 2 MPG from a 5 MPH difference. There were other differences, too, like number of stops and elevation changes, but I think the result still makes sense given what we know about drag. (In mixed driving, I typically see 25-27 MPG in the same car.)
Here's what the government has to say about our cars: https://www.fueleconomy.gov/feg/driv...0to%2075%20mph).
I believe drag is proportional to the square of speed. So as you could imagine, good fuel economy comes from a balance of getting the engine in its most efficient RPM range and keeping the aerodynamic drag in check.
When I was driving the GLI down from MO to GA, on my first day, I was going 80-85 MPH and got about 36 MPG average. The next day, I would say I was going about 75-80 MPH instead, and averaged 38 MPG. 2 MPG from a 5 MPH difference. There were other differences, too, like number of stops and elevation changes, but I think the result still makes sense given what we know about drag. (In mixed driving, I typically see 25-27 MPG in the same car.)
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swaangin (04-26-21)
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