Towing Gas Mileage Cover On/Off

[four winns 214]

I usually tow my boat with a cover on. Mileage most times is around 12mpg. Tonight, I towed 200 miles with it off and mileage was 10mpg. These numbers are taken from a trip computer that is always spot-on and the route is one I've done multiple times. Just curious, do others see such a difference? Truck is a 2011 Silverado with 5.3L, 3.42 rear end and Allison 6 speed. Cruise speed was 60-65 mph. Boat weighs 5950 on trailer.

 

[JB]

Re: Towing Gas Mileage Cover On/Off

A tight fitting cover greatly reduces drag. In your case that made A 20% difference in fuel mileage.

 

[jayhanig]

Re: Towing Gas Mileage Cover On/Off

I'm not suprised. Studies have proven that driving with the tailgate down in a pickup truck burns more gas than with it up, which seems counterintuitive. The reason is that an air burble develops which increases drag. I'd imagine the lack of a cover could easily have the same effect.

 

[H20Rat]

Re: Towing Gas Mileage Cover On/Off

I'm not suprised. Studies have proven that driving with the tailgate down in a pickup truck burns more gas than with it up, which seems counterintuitive. The reason is that an air burble develops which increases drag. I'd imagine the lack of a cover could easily have the same effect.

The air bubble actually serves to DECREASE drag, not increase it (it builds up with the tailgate up). The rolling air deflects additional air over the top, whereas the open tailgate ends up just creating a lot of turbulence.

Anyway, I've seen similar numbers towing my boat with the cover on vs off. It makes a fairly large difference!

 

[F14CRAZY]

Re: Towing Gas Mileage Cover On/Off

When I've towed my Bayliner up north with my Forester I figured having the cover on gained about 4 mpg

 

[hungupthespikes]

Re: Towing Gas Mileage Cover On/Off

I have about the same setup. 01 f150, 5.4 with just over 6000 lbs load. Have the same mpg results that you have, with or without cover.

The octane rating seems to help too, if I spend a dime extra for 89 octane. I'll get just over a mile better with/without trailer.
You might try a tank of 89.

 

[jayhanig]

Re: Towing Gas Mileage Cover On/Off

The air bubble actually serves to DECREASE drag, not increase it (it builds up with the tailgate up). The rolling air deflects additional air over the top, whereas the open tailgate ends up just creating a lot of turbulence.

Anyway, I've seen similar numbers towing my boat with the cover on vs off. It makes a fairly large difference!

Some say toe-may-toe; some say toe-mah-toe. I may have screwed up the explanation but I'm sure of my conclusions. I saw it on Mythbusters too.

 

[Home Cookin']

Re: Towing Gas Mileage Cover On/Off

I'm going to start driving my boat with the cover on then

 

[fishrdan]

Re: Towing Gas Mileage Cover On/Off

I tow a 14' jon boat (800#+-) with a car and covering the boat adds 3-4 MPG. Our Durango doesn't even know the boat is back there as it gets 15-16MPG normal highway mileage or towing the 14'er, it's within the Durango's slipstream,,, I guess. Towing our 18'er, the Durango's gas mileage drops to 8-10MPG. I should try covering the 18'er and see how the Durango's gas mileage responds...

That said, I usually don't tow with the cover on as it's a pain securing the cover tight enough for highway speeds. (A loose cover = a shredded cover.) If' I'm going over 100 miles, I cover the boat. Mainly for security, but mileage too.

 

[jkust]

Re: Towing Gas Mileage Cover On/Off

I've only ever towed with the cover on my sig boat. It is a snap down bow and cockpit, two piece cover. My mpgs are between 12 and 14 at a hair over 4000lbs towing with a 5.3liter with 3.73's and mpg robbing on demand AWD in OD. I'd hate to lose 20% of my mpgs but I've got so much gear and stuff in there I need the cover to keep it all in check and to keep prying eyes out of it when we pull into a business for dinner or whatever. That said I understand pro fishermen who tow a lot trailer uncovered.