Open road mileage is 1.8 at 65 mph WITH NO TRAFFIC

[MM in SouthTX]

I just did an 8.2 mile straightaway test with the cruise control set at 65, air temperature mid 60s, zero wind, zero accessories on except the fan on low, tire pressure at 40, on level ground at sea level.

Pushing my own air with NO TRAFFIC, the truck got 1.8 mi. per kWh over that stretch. I reset the trip odometer while doing 65 so no acceleration factor built-in.

I know that a lot of people report much better mileage, but I did this to point out how important having ANY sort of traffic is to improving your mileage. I took some video clips that I can post if people want.

The take home messages that open road mileage is far lower than mileage in traffic.

Planning to update this as I drive this stretch with wind added in.

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[RickLightning]

My Lariat's recommend tire pressure is 42 psi with the General Grabbers.

 

[Webbo85]

My Lariat's recommend tire pressure is 42 psi.

My stock Hankook DynaPro AT's are recommended 36psi. Depends on which tires the truck came with.

 

[Maquis]

My stock Hankook DynaPro AT's are recommended 36psi. Depends on which tires the truck came with.

Is that what’s shown on the door jamb of your truck?

 

[Webbo85]

Is that what’s shown on the door jamb of your truck?

Yup! I walked out and confirmed it.

 

[Ventorum94]

I just did an 8.2 mile straightaway test with the cruise control set at 65, air temperature mid 60s, zero wind, zero accessories on except the fan on low, tire pressure at 40, on level ground at sea level.

Pushing my own air with NO TRAFFIC, the truck got 1.8 mi. per kWh over that stretch. I reset the trip odometer while doing 60 so no acceleration factor built-in.

I know that a lot of people report much better mileage, but I did this to point out how important having ANY sort of traffic is to improving your mileage. I took some video clips that I can post if people want.
Did you take home messages that open road mileage is far lower than mileage in traffic.

Planning to update this as I drive this stretch with wind added in.

Spot on! If we could drive our Lightnings in a one-way tunnel, with fans moving air in our direction of travel (at the same speed we are moving) the resulting efficiency would be amazing. Heavy traffic on a divided highway is kind of like that imaginary tunnel, cutting air resistance dramatically. I’m convinced you don’t have to be “drafting” on the rear bumper of a semi to realize noticeable improvement in efficiency; being in heavy traffic even with smaller vehicles ahead, alongside, and behind, does wonders for range and efficiency (it hurts efficiency to be the only one on the road!).

 

[MM in SouthTX]

On the way back home in identical conditions except there was a 7 kn wind from 90° to my left, I set the cruise control on 70. I only got a 3.5 mile sample before I ran into traffic. The trip meter was bumping back-and-forth between 1.6 and 1.7 mi./ kWh.

 

[Bwanapete]

There have been posts about “air dam faults”. I have not looked under my truck but wonder whether there is some sort of automatically deployed air dam that helps range at higher speeds if it works and hasn’t been torn off due to road debris?

 

[lancersrock]

Well i drove 200 miles this morning with heat at 66 and seat on 1. Stayed at 72-74 cruise set and got 1.4. On my daily 150 mile drive yesterday i got 1.8 at 65, winter sucks.

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