I posted in another thread about my curiosity to find the sweet spot highway speed which optimizes fuel economy for my rig. I have a very mild level / lift and ~34 inch tires which has already reduced my fuel economy by over 2 mpg at speeds of ~75 mph. That's what I end up usually driving here in Florida.
My idea was to find the speed where the car will stay in Eco 4 cylinder mode on the flat highways in Florida. Theoretically that will provide the best highway fuel economy I can expect from my truck. I was on the highway yesterday and came across a wrecker pulling a crashed toyota corolla going slow on the Turnpike. I pulled in behind him and started to experiment. No head or tail winds.
Long story short, for my truck with current setup, my optimum speed to maximize fuel economy and still be going highway speed is 60.7 MPH. I have 34.1 inch tires, so the speed actually shows on my speedo as 57 MPH (see pic). This was the speed that the ECU would almost always maintain the truck in eco 4 cylinder mode. On uphill grades, it would drop out of eco mode but on the flat (this is florida remember) sections it would stay in eco mode the entire time. When I tried to set the cruise at 58 MPH (which is actually ~62MPH which my tires), it would toggle in and out of eco 4 cyl mode too often. At 60 MPH (actually ~64 mph), it would only go into eco mode on downhill grades and wouldn't even try on the flats.
So I reset the computer and after a stretch of about 10 miles with the cruise control set at 57 MPH (Actual speed = 60.7 MPH) I was logging 24.6 MPG avg. That to me is just ridiculously stupid good fuel economy for a mildly lifted and leveled, 4X4, gasoline engined, 1/2 ton truck with AT tires and 3.92 gears. Never would have expected that.
Now, you aren't likely to find me dawdling along in the right lane at 60 mph too often. You are basically a hazard if you drive that slow on Florida highways. But there are a lot of parts of the country and lots of roads where that is a reasonable and safe highway speed. Anyway, this curiosity that I had, I am very impressed with the results. I suspect that if I didn't have the extra drag of the lift, the sweet spot would be a few mph higher, where the ecu would still stay in 4 cylinder mode and still get exceptional highway mileage.
My idea was to find the speed where the car will stay in Eco 4 cylinder mode on the flat highways in Florida. Theoretically that will provide the best highway fuel economy I can expect from my truck. I was on the highway yesterday and came across a wrecker pulling a crashed toyota corolla going slow on the Turnpike. I pulled in behind him and started to experiment. No head or tail winds.
Long story short, for my truck with current setup, my optimum speed to maximize fuel economy and still be going highway speed is 60.7 MPH. I have 34.1 inch tires, so the speed actually shows on my speedo as 57 MPH (see pic). This was the speed that the ECU would almost always maintain the truck in eco 4 cylinder mode. On uphill grades, it would drop out of eco mode but on the flat (this is florida remember) sections it would stay in eco mode the entire time. When I tried to set the cruise at 58 MPH (which is actually ~62MPH which my tires), it would toggle in and out of eco 4 cyl mode too often. At 60 MPH (actually ~64 mph), it would only go into eco mode on downhill grades and wouldn't even try on the flats.
So I reset the computer and after a stretch of about 10 miles with the cruise control set at 57 MPH (Actual speed = 60.7 MPH) I was logging 24.6 MPG avg. That to me is just ridiculously stupid good fuel economy for a mildly lifted and leveled, 4X4, gasoline engined, 1/2 ton truck with AT tires and 3.92 gears. Never would have expected that.
Now, you aren't likely to find me dawdling along in the right lane at 60 mph too often. You are basically a hazard if you drive that slow on Florida highways. But there are a lot of parts of the country and lots of roads where that is a reasonable and safe highway speed. Anyway, this curiosity that I had, I am very impressed with the results. I suspect that if I didn't have the extra drag of the lift, the sweet spot would be a few mph higher, where the ecu would still stay in 4 cylinder mode and still get exceptional highway mileage.
