Fuel economy

[gluaisrothai]

Some data that might be useful for those considering the fuel economy impact of modifications to their 200 series.

I have:

• Dissent front bumper with winch
• Roofnest tent on a low profile backbone, plus a Bush Company awning.
• E&E skid plate and rear bumper
• 285/65/18 KO2 tires at 42psi cold.
• Harrop Supercharger
• 2 adults, 2 30lb dogs, drawer setup, fridge- overall load about 650lbs.

We are road tripping from Alameda CA to Austin TX and back, so plenty of time to play with speeds and assess fuel economy.

Currently holding 75MPH on cruise (which is a real 75MPH verified by GPS with the slightly oversized tires) we are getting 15.8 to 16.4 MPG over the last four tanks of fuel. OBD fusion shows fuel consumption in the 4.5-5 GPH range at that speed on level ground with an estimated 60hp used. We are at about 3000’ MSL.

We are running premium fuel due to the ‘charger.

Pushing the speed to 80MPH results in about a 15% increase in fuel consumption.

Reducing the speed to 68MPH doesn’t seem to save much fuel over 75MPH.

Higher elevations reduce fuel consumption due to reduced drag- noticed this on the way down through southern CO.

 

[skrypj]

Currently holding 75MPH on cruise (which is a real 75MPH verified by GPS with the slightly oversized tires) we are getting 15.8 to 16.4 MPG over the last four tanks of fuel.

Is that indicated by the gauge cluster or hand calc'd? I guess your tire size is not too much bigger than stock so the gauge cluster shouldnt be off too much.

The last couple of times I did longer drives at 80mph I think I was getting around 17 in my 2018 LX, including accounting for my 315/70R17's. When I went to Moab a few weekends back I was getting nearly 20 mpg when I stopped for gas 3/4 of the way there, but that drive tends to be a bit slower, probably 65-70 on average.

 

[bloc]

Just for a point of reference when I went from stock dunlop tires to 42psi LT285/65R18 KO2s at ~73mph cruising speed I lost over 2mpg after adjusting everything for tire size.

Switching to an even taller P-metric 285/70R17 Toyo OC AT3 almost completely recovered the loss, averaging maybe .5mpg drop. This was with an otherwise stock Landcruiser plus the 10mm OE front spacer, doing the same run from central Texas to SW CO over probably two dozen trips, so very similar conditions.

How aggressive of a AT tire and whether someone is on LT-metric or ISO/P construction will really impact fuel economy, and is worth specifying when people post their data.

 

[gluaisrothai]

Just for a point of reference when I went from stock dunlop tires to 42psi LT285/65R18 KO2s at ~73mph cruising speed I lost over 2mpg after adjusting everything for tire size.

Switching to an even taller P-metric 285/70R17 Toyota OC AT3 almost completely recovered the loss, averaging maybe .5mpg drop. This was with an otherwise stock Landcruiser plus the 10mm OE front spacer, doing the same run from central Texas to SW CO over probably two dozen trips, so very similar conditions.

How aggressive of a AT tire and whether someone is on LT-metric or ISO/P construction will really impact fuel economy, and is worth specifying when people post their data.

My tires are LT and probably responsible for a lot of the reduced mileage from stock.

 

[gluaisrothai]

Latest leg- Deming NM to Tucson AZ- 75MPH- 14.4MPG. I believe wind was a factor.

Based on what I’ve read in other threads my speedometer is accurate due to the slightly oversized tires but my odo likely reads under by about 3%. And my OBD fuel economy reads a little off due to the fuel pressure regulator tweak that the Harrop install uses.