The best gas mileage on my ST1100 has been 43 mpg, is something wrong?

Did a fuel check last year just to see if it was running OK. With a pillion and top box/ tall screen, 52 miles to one proper imperial gallon.
I don't tend to try for high mpg and keep the motor between 3 and 6000 rpm most of the time, on average UK roads speeds would be anywhere between 50 and 70 mph. I was very pleased with the 52. I think it returns nearer 40 when fully loaded at European highway speeds, 80 plus mph.
Just to clarify it would be held at around 3000 rpm most of the time and up to 6000 for overtakes and joining manoeuvres etc.
Upt'North.

I average 43-45 imp gal on the ST, on the vstrom 650 I've seen high 60's but mostly average around 62mpg, I do tend to work the engine though, if I nursed them I'd get slightly better mileage but grin less.

Anecdotally the specs say we can expect 300 mile range or 500km range with these bikes. Given it holds 7.3 US Gallons or 6.01 Imperial or 28 litres that translates to 41mpg US , 49.9mpg Imperial and 5.6L/100km. I think it would be safe to say anything around that is normal, above that is great
There are a lot of variables that come into play, tire pressure, quality of fuel, Altitude, California spec. In Ontario our fuel is laced with a minimum of 10% ethanol possibly 15% (some stations sell premium without ethanol, they aren't always easy to find). The Ethanol impacts mileage, so that is a bit of a challenge some of us experience.
I have a '97 California spec bike with ABS (adds a few pounds) It has the PAIR system removed. For the most part on the highway I run at a true 114km/h 3200-3300rpm. I have electronic cruse control and I'm in the zone of 49 mpg Imperial. When I've done 240 miles my gauge is hovering around the 1/4 full mark, my fuel light comes on around the 260 mark and when I fill up I tend to put in between 22-24 litres at that point, which leaves me close to a gallon of fuel left to allow me to hit that golden 300 mile per tank goal. My 1990 returned the same figures.

Good point, Kiltman. My figures were on 99 octane, nil ethanol fuel. So good figures have to be offset by about 10% more expensive fuel.
Upt'North.

Gerhard said:

I have always wondered if you really get better mileage from a lower windshield?

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My guess is if we could get into one of those test wind tunnels with a somebody sending that test smoke over us we would find an optimum height for a given rider and windshield for lowest µ or C[SUB]​d[/SUB].

I use 91 (?) Octane gas and try to keep my tires at 42/42. My factory windshield fully lowered around town so probably doesn't make much difference. On the freeway fully up it's just below eye level and cuts wind noise in the helmet. I can slump a little to get under the top. No top box. My typical mileage is 43-44mpg. With more freeway riding it's 48-50 if paying attention to the throttle. If I were a smoother rider the mileage might go up a skosh. Lightening— uh... the ST by 40lbs doesn't seem to affect mileage.

I can't remember what my mpg used to be, but I always used to set the trip at each fill-up. I'd be starting to look for fuel at 220, start getting worried at 240 and the few times that fuel stations didn't present themselves I'd be breathing a sigh of relief at 250. There was always more fuel left than I imagined. Typical riding was 2-up touring / camping and daily 6 mile commutes twice a day.

Well I bypass the vacuum fuel cut off valve and will check over a few tanks. At minimum I hope the gas smell goes away.

jfheath said:

I can't remember what my mpg used to be, but I always used to set the trip at each fill-up. I'd be starting to look for fuel at 220, start getting worried at 240 and the few times that fuel stations didn't present themselves I'd be breathing a sigh of relief at 250. There was always more fuel left than I imagined. Typical riding was 2-up touring / camping and daily 6 mile commutes twice a day.

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I know just what you mean, that fuel light takes forever to come on and when it finally decides to show itself you've still got 50 miles left. I also think that 250 miles is plenty long enough between fills and would usually top up after two to three hours riding. It's nice to know you can run the tank so low though and still have plenty left. Famous last words?
Upt'North.

Upt' North said:

It's nice to know you can run the tank so low though and still have plenty left. Famous last words?

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Probably ! And I would replace that word 'can' with 'did'. It was a huge sigh of relief, and I had been riding VERY economically for the last 20 miles, waiting for the splutter and cough. I had expected it to be out of fuel at 240.

PhotoDoctor said:

Well I bypass the vacuum fuel cut off valve and will check over a few tanks. At minimum I hope the gas smell goes away.

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did you also check the #3 plug for fouling? If not, take a minute to check that and clean it up if its fouled.

I had two ST1100's- one without ABS and one with. On both of them my MPG for normal riding was always between the high 40's to 55 miles per imperial gallon. This converts to somewhere between 40 and 45 miles per U.S. gallon so based on my experience it sounds like you are doing alright.

Here's my 2 cents... guys worry too much about MPG. Does your bike run well? Accelerate smoothly with no flat spots or stumbling? If yes then stop worrying about MPG! Ever hear the expression "Your Mileage May vary"? There are lots of factors, your weight, your roads, your terrain, your altitude, your throttle control, your tires, on and on.

If you want to ease your mind about MPG get a scooter. Otherwise worry less and ride more.

dwalby - I think you may have something there - I bypassed the vacuum shut off and went for a 165.3 mile ride and used 3.139 gallons which works out to 52.66 mpg. (That is 10 mpg better than any check I've done on this bike in the 4,000 miles that I've owned this one)

While I had the tank cover off I checked the pre-filter that goes to the carb slide vacuum area and it was gone so I replaced it. On the 165 mile ride I met up with a friend who just rebuilt his 1970s BMW R750 with rings and new valve seats so we kept the revs low - I followed him and seldom exceeded 3000 rpm which is about 60 indicated mph.

Anyway this is promising - I'll have to run some more at more normal speeds to be certain but this is a huge jump in mileage for this bike.

Sadly, I did not check the #3 plug for fouling before I did this run. I'm going to have to take the vacuum shut off apart and see what is up with it. I truly hated the vacuum petcocks that Honda used on the GL500 and GL650 as if they failed you had zero gas flow. I think I'm going to find your are right and gas was being sucked into the #3 intake manifold killing the fuel mileage. Although the bike ran excellent.

PhotoDoctor said:

Sadly, I did not check the #3 plug for fouling before I did this run. I'm going to have to take the vacuum shut off apart and see what is up with it. .... I think I'm going to find your are right and gas was being sucked into the #3 intake manifold killing the fuel mileage. Although the bike ran excellent.

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glad to hear of your success.

I suspect what you'll find is a small tear in the diaphragm, so it can't actuate the valve fully, and instead allows some raw fuel to follow the path down the vacuum line into the #3 cylinder. If the bike's running fine the fouling may be minimal, but it only takes a minute to pull the plug and see for sure what condition its in.

Smc091064 said:

I own a ST1300, but some other ideas are tire pressure and maybe the wheel bearings are going bad or excessively worn. From what I read they should be replaced about every 40/60,000 miles (?). My ST1300 uses premium fuel, I have noticed that I get slightly better gas mileage with premium (not sure if the ST1100 takes premium). Good luck

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Just changed my rear tire and found the bearing a little stiff and the caliper was dragging. I get fairly good mileage, but it sounds pretty logical issues like that can slow the bike down.

Whooshka said:

Here's my 2 cents... guys worry too much about MPG. Does your bike run well? Accelerate smoothly with no flat spots or stumbling? If yes then stop worrying about MPG! Ever hear the expression "Your Mileage May vary"? There are lots of factors, your weight, your roads, your terrain, your altitude, your throttle control, your tires, on and on.

If you want to ease your mind about MPG get a scooter. Otherwise worry less and ride more.

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I agree completely if someone is obsessing about it. However, an occasional checking of current fuel efficiency and comparing it with past numbers once in a while is a different story and can be helpful. A seemingly well running engine does not indicate a lack of a problem. Noting a change in fuel efficiency is a good early warning indicator of a potential problem that can be taken care of before it becomes a more serious problem. A couple of good examples of what an increase in fuel consumption for no apparent reason can indicate, as many on this forum have noted, is a thermostat that is on its way out even before the temperature gauge starts the two-bar three-bar dance or a dragging rear brake (SMC).

I am about 10mpg in my hemi 2500 ram, So the 40's I get on my ST1100 seem like money in my pocket, so much I get a Yohoo and a whatchamacallit candy bar to celebrate the savings.

Andrew Shadow - you are spot on!

Andrew Shadow said:

I agree completely if someone is obsessing about it. However, an occasional checking of current fuel efficiency and comparing it with past numbers once in a while is a different story and can be helpful. A seemingly well running engine does not indicate a lack of a problem. Noting a change in fuel efficiency is a good early warning indicator of a potential problem that can be taken care of before it becomes a more serious problem. A couple of good examples of what an increase in fuel consumption for no apparent reason can indicate, as many on this forum have noted, is a thermostat that is on its way out even before the temperature gauge starts the two-bar three-bar dance or a dragging rear brake (SMC).

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Yes I whole heartedly agree. I also check my mileage every few tanks, and not by the gauge in the dash, you gotta do the math.

I've got a gas gauge. It's close enough. I won't obsess over milage and do tank math. When the gauge gets low fill and go.