Drafting to improve MPG

[2015 Blue RT]

I've been trying a few non-scientific tests on my commutes. Now that I'm free of fuel additives and running subsidized 93 premium, my average MPG is around 48-49. Using the instant MPG gauge on the bike, when possible I've tried drafting (nothing smaller than an SUV, never closer than the 2 second rule) to see what effect it has on my mileage. I found I get usually 15-20 MPG more in a 60 MPH zone. I tried this on the Interstate (70 zone) today behind a U-haul box truck & saw around +10 MPG. It was more hilly than my usual two lane commute though.

 

The odd thing to me is I feel more wind (buffeting) in doing this, but there's clearly less wind resistance on the bike.

 

This has been a big help with the high cost of gas lately.

[Bernie]

I think you could see even better results by closing up the distance, similar to a nascar driver. It should also eliminate the buffering you are feeling.

[Skywagon]

Although your mileage will likely increase, your safety will decline significantly. If there is a road hazard, hole, board, tire carcass, animal, etc, your ability to swerve and miss it is severely compromised.

Personally for me I try to stay back as far as I can and still stay at the same pace as traffic

 

I picked up this habit because if an accident I had in the 80’s. I was tight on a dump truck in the winter to stay warmer. All was well until a roll of wire fell out, locked up my wheels, and down I went on the freeway @ 60 mph. 
 

Here in Houston there is shiite all over the roads. 
 

If you need to do that to save gas, stay on your toes. 

[dirtrider]

On 5/8/2022 at 10:06 PM, 2015 Black RT said:

I've been trying a few non-scientific tests on my commutes. Now that I'm free of fuel additives and running subsidized 93 premium, my average MPG is around 48-49. Using the instant MPG gauge on the bike, when possible I've tried drafting (nothing smaller than an SUV, never closer than the 2 second rule) to see what effect it has on my mileage. I found I get usually 15-20 MPG more in a 60 MPH zone. I tried this on the Interstate (70 zone) today behind a U-haul box truck & saw around +10 MPG. It was more hilly than my usual two lane commute though.

 

The odd thing to me is I feel more wind (buffeting) in doing this, but there's clearly less wind resistance on the bike.

 

This has been a big help with the high cost of gas lately.

Morning  2015 Black RT

 

15-20 MPG more in a 60 MPH zone tells you that your testing method is flawed. 

 

You probably need to run at least a 10 mile average, a longer yet average would be even more accurate.

 

Try a weeks worth of commuting using no drafting then try a weeks  worth of commuting using as much drafting as you can, then compare the average fuel economy of each. 

[TEWKS]

Not trying to be the “safety police” here but another thing to consider. 
 

 

[dirtrider]

Quote

Not trying to be the “safety police” here but another thing to consider. 

Morning TEWKS

 

Yep, that can be a problem, only good side is that a motorcyclist can usually hear the truck trailer tire starting to go well before it comes apart.  

 

 

[wbw6cos]

I have had numerous trailer tires blow and never heard or felt them.   Yeah, stay away from BIG TRUCKS!   

[TEWKS]

William beat me to the same answer.  

Yeah agree, retreads will chunk and flap which should warn a rider but, I’ve had tires suddenly explode on a trailer that scared the crap out me!  And, I was up in the cab. 

[Lowndes]

Back in the 60's I had a Honda S90 going to school in Texas.  It's max indicated speed was 62 mph.  Several of my friends rode bigger bikes that would go much faster.  They hated having to go slow for me and I hated holding them back.  We were going somewhere one weekend on an interstate type highway when a "large truck" slowly passed us and I could feel the "bow wave" and then the "suck" as the end of the trailer went past so I pulled in right behind it.  I found that I could pull in the clutch, even shift into neutral and turn the engine off if I stayed within 10-15 ft of the end of the trailer, directly behind a set of wheels, and sat up as tall as possible, me acting as a sail in that wind.  The air coming from the top and sided of the trailer curling in to fill the void and pushing me and the bike was enough to get me going 70-80 mph.  The scenery wasn't that great unless you liked license plates, warning signs and dirt grafiti, but talk about mileage!!  Pretty soon I realized that anything on the road those truck tiers hit would be bad news for me and the S90. That thought slowly killed the thrill but I could definitely FEEL the effect of drafting.  There is a trade-off for everything.

[Paul De]

Agree with Tewks about drafting or being anywhere near big rig trucks.  I won't even stay near them in my car.   Drafting is great for go fast racing, but not so much for commuting. Gasoline at any price per gallon won't get me to do it. I either fall back, or zoom past, but I'll never dawdle!

 

My wife once asked me why when I pass a big rig on the interstate I always really up my speed and zoom past and then settle back into my pace.   Aside from the "don't hang out in a blind spot" you get in drivers ed, I started pointing out all the retread debris along the roadside, especially how much is really big chunks and how frequent this type of an event occurs .   I don't want to tangle with that stuff even in a car and over the years we have seen enough tread shedding happen in the moment to convince me I'm not being weirdly nervous anywhere near big rig trucks.  My wife now has adopted the zoom past when over taking a big rig as well.

[wbw6cos]

The tire on a big rig doesn't have to blow.  It can run something over and kick it up.  

[TEWKS]

What Lowndes describes is exactly the push you feel on your back when you put the RT windscreen in its highest position at highway speeds. 
 

So, with that theory at work, I say put your windscreen up and save fuel! 

[Hosstage]

I tend to ride a little reckless more than most, but I do not mess with the big trucks. Out and around in a hurry, or lay back to dodge whatever kicks up. I've been next to a truck when the tire blew, there was no warning. Luckily I was in a car and no damage.

I've honestly never worried too much about gas mileage in any vehicle, I drive for the conditions and fill up when necessary. It's nice when I exceed my normal mpg, but it's not something I chase. If I get substantially less mileage for a stint I can usually figure out why, bucking wind, driving higher speeds, etc. It all evens out in the end as long as the vehicle is in good running order.

[dduelin]

I have a Honda NC700X that tops out at 99-100 mph but I found that if I hang about 5 or 10 feet behind my friend's ST1300 I can pick up an extra 6 or 7 mph. That's about the only dumb thing I've done that I care to share here. The Two Second Rule works for following distance but not for avoiding debris in the roadway that the cars and trucks either straddle or kick up in our face shield.

[roadscholar]

Drafting in racing is part of the sport. Doing it on the street is stupid, many things can happen, none of them good.  

[Hosstage]

34 minutes ago, roadscholar said:

Drafting in racing is part of the sport. Doing it on the street is stupid, many things can happen, none of them good.  

Unless you're racing on the street. Good things happen, like beating your friends. Bad things can happen too, like losing to your friends......

[alexvtr]

7 hours ago, dirtrider said:

Morning TEWKS

 

Yep, that can be a problem, only good side is that a motorcyclist can usually hear the truck trailer tire starting to go well before it comes apart.  

 

 

Another good telltale is the smell.

If it starts to smell like burnt rubber, get outta there; a tire is about to go bang.

This method has saved me a few times.

[Skywagon]

We’re getting pretty far off the gas mileage question and unfortunately I’m the turd who started the diversion from the ops question. That said, let me do it one more time😁

 

When I was in college and broke as a convict, I carried 3-4 retreads in my trunk all the time. That’s about how many it would take to make a round trip home. We called them Goodyear Maypops. May pop at any moment. Back in the 70’s the quality wasn’t near as good as today. Headed home. Whap whap whap pow. MF. I bet I heard that sound a dozen times or more. Every time one blew I was out $6.  Hey don't trivialize the $6.  I was making $2/hr cash butchering livestock and slinging BBQ.   Each May Pop was about a 1/2 day of work.

 

ok back to the mileage by draft thread. 

[2015 Blue RT]

12 hours ago, Skywagon said:

Although your mileage will likely increase, your safety will decline significantly. If there is a road hazard, hole, board, tire carcass, animal, etc, your ability to swerve and miss it is severely compromised.

Personally for me I try to stay back as far as I can and still stay at the same pace as traffic

 

I picked up this habit because if an accident I had in the 80’s. I was tight on a dump truck in the winter to stay warmer. All was well until a roll of wire fell out, locked up my wheels, and down I went on the freeway @ 60 mph. 
 

Here in Houston there is shiite all over the roads. 
 

If you need to do that to save gas, stay on your toes. 

Funny you mention that. I followed a Jeep SUV to work a couple of weeks ago pre-dawn, and there was a fairly massive deer hit and in our lane. I was not so close that I couldn't avoid it- we both did by banking right. The blood trail is still on the road.

 

I think I fared better in that incident than I would have solo, especially considering the car that hit it was on the oncoming side of the road with their headlights still on. On my pre-dawn rides I like to follow a car or SUV if possible due to animals. In 40 years of riding (much of it rural) the only animal collision I've had was on this bike when a buzzard hit me (chronicled in an older post here last year) when I disturbed its lunch.

 

Bottom line for me is literally YMMV. Life is a risk every day from the time you wake up. What works for one doesn't for another & that's OK.

[Hosstage]

Many years ago there was a contest among the automotive magazines to get the best mileage out of a gallon of gas in a vehicle at 55 mph on a closed course. Car and Driver, being the irreverant group they were, employed a full size van with its rear doors tied open to draft behind and drove up tight on its bumper, of course winning the contest. While technically not against the rules, they did feel a bit guilty, and the following year the rules were rewritten with tighter specs.

There's always gotta be one in the group that plays for the kill shot.

 

[szurszewski]

On 5/9/2022 at 4:17 AM, dirtrider said:

Morning  2015 Black RT

 

15-20 MPG more in a 60 MPH zone tells you that your testing method is flawed. 

 

You probably need to run at least a 10 mile average, a longer yet average would be even more accurate.

 

Try a weeks worth of commuting using no drafting then try a weeks  worth of commuting using as much drafting as you can, then compare the average fuel economy of each. 

I also find it hard to believe you’d see a true increase of 25% or even close to that. I can get my instant read mpg to display 99 in my hybrid - if I reset when going downhill on the highway, but it doesn’t equate to true efficiency. 
 

DR’s suggestion would get you a much more real world answer. My scientific side is curious, but my risk management side agrees with all the posts saying it’s a bad idea (because it is - for your safety and the safety of those around you). 
 

As to why you’re seeing that spike in mpg? Initially I’d wonder if maybe you see a quick spike because you’d sped up to get in position and then backed off the throttle, thus incorporating at least some “coasting” time into the calculation. Also possible that by picking one truck to follow you are lowering your overall speed or maybe at least keeping a more constant throttle. My wife and I have about the same “cruising speed” on the highway when taking long trips, but I will consistently get more miles out of a tank/higher mpg because I am more likely to keep to my average speed where she will slow down/speed up more frequently (for instance, I’ll spot that slow truck far ahead and plan my lane change to fit into gaining traffic from behind - she will often wait until she’s closer to catching up and have to slow for a bit then speed up to match traffic in another lane). 
 

So if you wanted to keep it really scientific you’d have to ride your “normal” way for a week, draft as much as possible for a week while estimating what your typical when-drafting speed was, then do a week where you just tried riding at that speed constantly (not as much moving around in traffic as many moto riders do and most trucks do not). 
 

But, again, I’d suggest skipping the drafting portion of the test. 

[Michiganr80rt]

I am late to the game about truck tires. Sunday I was driving the car on I-80 in northern Indiana. I smelled a hot tire and then saw the truck in the second lane with the hot tire. I moved to lane four and tried to get ahead of the debris. As I passed the tire was starting to come apart. Looking in the mirror I think a car ended up in the center barrier trying to avoid the big chunks about 15 seconds after I passed.

 

I do not like to be near trucks.

 

However, in 1974 I learned that my Honda CL175 could do over 70 mph and get 75 mpg if it was drafting a big truck. Young and stupid.

[gary45]

Horsepower comes from burning fuel, Horsepower is needed to move through air, doubling your speed takes about 4 times the Horsepower, if you are drafting the reduction in Horsepower needed to maintain the same speed can result in saving quite a bit of fuel.

[Hosstage]

I do a lot of group rides, I get better mileage when riding in the middle or the back rather than leading the line.

[szurszewski]

4 hours ago, Michiganr80rt said:

 

However, in 1974 I learned that my Honda CL175 could do over 70 mph and get 75 mpg if it was drafting a big truck. Young and stupid.

I got a ‘71 Fiat Spider when I was 18; that thing was light enough that if I got RIGHT up behind a semi on a flat stretch of freeway, I could put the car in neutral and just sort of get towed along for a while. I don’t remember ever having a passenger who appreciated me showing them that trick. 

[DeltaBravo]

I drafted an 18-wheeler for about 70 miles or so back in 1969 on my Bonneville.  The driver knew I was there and acted accordingly with long passes, etc.  I only a few feet from the trailer bumper and completely out of the buffeting.  I made it to 78 miles on my trip meter and decided to bail out for gas (Bonny had a 2.5 gallon tank and usually got 40 mpg).  Filled the tank with a whopping 1 gallon of gas - 78 mpg.  Couldn't find another to draft for the rest of the day.  It was "summer" in Wyoming (June) and I was freezing!  The draft really helped.  And NO I would never do it again!

 

Coldest I've ever been was that east to west ride in June and a north to south ride in July 1999 on my K12LT with heated everything!