Causes for sudden jump in fuel consumption 2017 RTL

[askitee]

About 3 weeks ago I was still getting around 400+ kms from a tank of fuel.

Two Saturday's ago the chief cook and I took a run to one of our favorite country cafes (round trip about 270km) and had to stop for fuel.

Then on this most recent long weekend, same problem - a trip North up the coast a round trip of 900km's - needed four tanks of fuel to make the trip.

Both journeys were very steady paced.

I've jacked the Spyder up and checked wheel rotation for any sign of restriction, breaks for grabbing, axle tension. The engine feels like its running smooth (i.e no audible sign of a blocked injector). The one thing the 4 days of riding had in common was unusually high humidity (I could be clutching at straws looking for a possible cause)

[PMK]

Humid air is less dense and makes less power. If it was hot and humid even worse for making power.

Honestly not sure why, is it possible the fuel quality or octane / additives differed.

[Peter Aawen]

Have you been ryding in all the smoke that's been around Askitee? If so, it could be worth checking &/or cleaning/replacing your air filter! I don't think we've had quite so much smoke over here in South Oz as some parts of the East Coast, but even with what we have had I've noticed the air filter getting clogged fairly quickly!

Did a few local rydes between Christmas & New Year in the Adelaide Hills smoke zone, and on the first longish run I did for 2020, I noticed exactly the same thing as you - poor fuel economy & a need to top up just to get to a place I usually reach easily on less than a tank full, altho there was no really discernable loss of power!?! Scratched my head over it for a bit, but being an old diesel type, I checked & cleaned the fuel filter & the air filter before doing anything else just out of habit. And while the Fuel filter was fine, the a/mkt oil filled foam air cleaner took a few rinsings to get all the smokey smelling crud out - but once I had cleaned it all out, I rode home easily on less than a tank of gas as per normal, despite taking the 'more exciting' route too, so if anything, my fuel economy shoulda been worse on the way home!!

I've only done one longish run since, without getting quite as far as any measurable or noticeably worse fuel economy, but just to be sure to be sure, before we left for Melbourne on the 16th, I cleaned the air filter again..... and cleaned out almost as much smoke smelling fine 'soot' once again; so I don't think it was too far off having a fuel economy impact!!

I'm only calling it 'soot' for want of a better descriptor - it was a dirty reddish brown to black very fine gritty stuff that's about as fine as Simpson Desert sand, only it smells more like smoke than desert dust! But if you've had a lot of smoke around like most of the rest of the East/South Eastern Aust Coast, your fuel economy problem could well be at least partially due to a smoke/fine ash filled air filter..... and the high humidity is very likely to make the impact of that a lot worse too! So at the very least, it's worth checking/cleaning your air filter I reckon!

Good Luck!

[bushrat]

Askitee, I've had the same experience on my F3L recently while ryding in Central Florida over the winter. Last couple of fill-ups, my mpg has dropped significantly from what I was experiencing in Nov/Dec, and even that was somewhat down from mpg performance back in Ontario, during the summer and early fall. I would think certainly weather-related in my case - both temp and humidity; possibly also different additive mixture. I do know that it's difficult to ensure my F3L tank is being filled to same level each time, but I do try to get it all the way to top each time. So, I don't think that's much of a factor for me. I do know that when I haul my fairly light m/c trailer, even with a slight load, mpg performance can drop by 20%. But haven't been dragging my trailer along recently. Peter Aawen is very likely on to cause in your case, I suspect. As, I believe, is PMK - heat/humidity related reasons. Over the years of my driving experience, whether it be cars, trucks or bikes, I have always, without fail, gotten my best mpg performance right after a summer rain, when the air had cleared out a bit and the temp had dropped - noticeable improvement in fuel consumption, even at the very times when I was driving more aggressively.

[h0gr1der]

Do you guys have Winter and Summer fuel blends down under? Some folks have noted significantly different performance levels between the two. Are you filling up at the same places? I once ran a stretch of superhighway through Oklahoma that had a certain brand assigned to lengthy sections, and upon filling up with that brand I lost so much power that I thought something was wrong with my bike. As soon as I got off of that monopolized stretch and filled up with a premium grade fuel all my performance was back.

[carbonation]

One would assume that an increase in humidity would reduce MPG because some oxygen is replaced by moisture. You can only have so much stuff in a given volume of air. ECU's compensate really well in modern vehicles, so there is much less of an effect.
bushrat in Florida isn't going to see a winter/summer changeover in fuel blends, it's the same all year around.
I side with Peter, dirty air filter choking breathing, reducing power, and requiring more throttle input for fun factor results.
Generally speaking, fuel is fuel. It's (for all practical purposes) identical, traded as a commodity, until it gets put into the tanker truck. Ethanol, if required is added first, then fuel with the additive dosed along the fill. It is quite possible you could buy Shell made basestock dosed with Amoco Invigorate at your BP station. Or vice versa.
Google up CBOB for a start on info. More there than even an oil thread could handle.

[ARtraveler]

Askitee, I've had the same experience on my F3L recently while ryding in Central Florida over the winter. Last couple of fill-ups, my mpg has dropped significantly from what I was experiencing in Nov/Dec, and even that was somewhat down from mpg performance back in Ontario, during the summer and early fall. I would think certainly weather-related in my case - both temp and humidity; possibly also different additive mixture. I do know that it's difficult to ensure my F3L tank is being filled to same level each time, but I do try to get it all the way to top each time. So, I don't think that's much of a factor for me. I do know that when I haul my fairly light m/c trailer, even with a slight load, mpg performance can drop by 20%. But haven't been dragging my trailer along recently. Peter Aawen is very likely on to cause in your case, I suspect. As, I believe, is PMK - heat/humidity related reasons. Over the years of my driving experience, whether it be cars, trucks or bikes, I have always, without fail, gotten my best mpg performance right after a summer rain, when the air had cleared out a bit and the temp had dropped - noticeable improvement in fuel consumption, even at the very times when I was driving more aggressively.

See post #5 about "winter blends." That may be the culprit.

[Peter Aawen]

Do you guys have Winter and Summer fuel blends down under? Some folks have noted significantly different performance levels between the two. ..........

The vast majority of Australia doesn't get (or need!) different fuel blends for different seasons &/or higher altitude, altho the changing blends thing does occur in/around the (very) few spots this Continent has that are high enough to get snow every now & then.... and AFAIK, the closest of all of those few spots is about 800km South of where Askitee usually is in the Hunter Valley Region of NSW. And then given his 900 km trip North returning poor fuel economy too, I'd guess that it's not likely to be that!

[fatboy]

riding into the winds a bitch

[askitee]

Have you been ryding in all the smoke that's been around Askitee? If so, it could be worth checking &/or cleaning/replacing your air filter! I don't think we've had quite so much smoke over here in South Oz as some parts of the East Coast, but even with what we have had I've noticed the air filter getting clogged fairly quickly!

Did a few local rydes between Christmas & New Year in the Adelaide Hills smoke zone, and on the first longish run I did for 2020, I noticed exactly the same thing as you - poor fuel economy & a need to top up just to get to a place I usually reach easily on less than a tank full, altho there was no really discernable loss of power!?! Scratched my head over it for a bit, but being an old diesel type, I checked & cleaned the fuel filter & the air filter before doing anything else just out of habit. And while the Fuel filter was fine, the a/mkt oil filled foam air cleaner took a few rinsings to get all the smokey smelling crud out - but once I had cleaned it all out, I rode home easily on less than a tank of gas as per normal, despite taking the 'more exciting' route too, so if anything, my fuel economy shoulda been worse on the way home!!

I've only done one longish run since, without getting quite as far as any measurable or noticeably worse fuel economy, but just to be sure to be sure, before we left for Melbourne on the 16th, I cleaned the air filter again..... and cleaned out almost as much smoke smelling fine 'soot' once again; so I don't think it was too far off having a fuel economy impact!!

I'm only calling it 'soot' for want of a better descriptor - it was a dirty reddish brown to black very fine gritty stuff that's about as fine as Simpson Desert sand, only it smells more like smoke than desert dust! But if you've had a lot of smoke around like most of the rest of the East/South Eastern Aust Coast, your fuel economy problem could well be at least partially due to a smoke/fine ash filled air filter..... and the high humidity is very likely to make the impact of that a lot worse too! So at the very least, it's worth checking/cleaning your air filter I reckon!

Good Luck!

I'll check that for sure - never even gave it a thought. Thanks

[Cobwebs]

Different diameter tyre fitted? What colour is your exhaust.My favorite……………. stick it in top gear

[askitee]

Well looks like it was the high Humidity. The last Friday of each month is Bike Night in one of our nearby cities about 280km round trip. Fuel consumption was back to normal.