Do I have an MPG issue?

[AZST]

...or is the bike playing tricks on me?

2 weeks ago, I noticed after filling up w/ Chevron highest octane, that I lost one "bar" after only 23 miles. Then, I lost my second "bar" after 54 miles. Strange, so I just kept riding and it seemed like my gas was going down alot faster than usual.

So today, I did some testing in the desert.

Facts:
04ST, 22,300 miles
Air cleaner (OEM) has about 1000 miles
Original plugs
Orig T-Stat
Bike temp gauge has stayed on 3 bars since new. Always.
Bike has Turbo Tom's FPR for about a year w/ no issues.

The Test:

Conditions: 75 degrees, slight wind.

Filled the tank at Chevron-High octane on the sidestand, right to the top of the neck.
Rode the bike at 70 mph, shield in lowest position on a level surface with no stops. At 33.4 miles, I lost my first "bar" on fuel gauge.

At 44.5 miles, I lost my second "bar".

Meanwhile the MPG calculator was reading that I was getting between 43mpg and 52mpg (keep in mind that my throttle-on was relatively constant)

At 57 miles, I gained one "bar" back. ?????

At 58.5, it dropped back down to two "bars" gone.

I should not be getting approx 30mpg. I thought it might be t-stat but my gauge suggests otherwise. It is my assumption that the plugs need a changing.

Any other suggestions?

--Bryan
04ST1300A
:04biker:

[sherob]

How does it start... fast and furious or slow and sluggish? That's how I found my ST before changing the plugs :)

[AZST]

How does it start... fast and furious or slow and sluggish? That's how I found my ST before changing the plugs :)

Orig battery. The bike had been cranking over slower lately. Recently bought a Battery Tender and it seems to crank over like it normally does.
Usually on start up, the idle runs to 1900 r/min and then smooths out about 1100 r/min. Normally, I don't ride until two "bars".

Also should mention that it does not seem sluggish off the line or in traffic. Smooth as always.

Oil level is right in the middle of the glass and recently I topped off the green fluid.

--Bryan
04ST1300A
:04biker:

[Pat Thompson]

I've noticed on my '06 that the gas gauge drops down off the full bar quite quickly. It seems to drop more slowly as I get deeper into the tank and stays at 2 bars remaining for quite a long time before finally flashing the last one. One time I did the math for a tank to tank fill-up and ended up with 43 mpg and I was filling up at just less than 300 miles.

I think it's just characteristic for the guage to drop down quickly. Just figure your milage the old fashioned way a couple times to see if you really are having abnormal mpg problems.

[electrajoe]

I don' have one of those "new fangled" bikes, but have been told "don't trust electronic fuel read-outs on the ST1300. " Heck even my old 1991gauge is not accurate, 200 miles on the first half and 60-90 miles on the second half.

The only true was is to fill it up, ride a tank (maybe a 100 miles) then fill to same level as before divide miles by gallons used.

Or could be a bad batch of fuel.

[dteel]

Bryan, I'd just let it be for awhile and see what happens. Changing the plugs isn't a bad idea but I wouldn't hold out much hope that it will change anything.

Do you always buy your gas from this Chevron? It's pretty late in the winter to be blaming this on the change to winter blend, I know you ride more than that. Could be Chevron got a bad batch of gas. Keep track of your mileage for the next few tanks, compare it to previous tanks. My mileage has really suffered this winter. I haven't gained any weight so that's not to blame. I have a couple thousand less miles than you, but still mighty similar, both in maintenance and situation. Only real difference is our respective weights. I have been getting about 8-10 mpg less than you averaging 36 mpg or so. The statistics I’ve been keeping are showing that the fuel mileage indicator on the bike is actually pretty accurate generally within 2-3%. I have a speedohealer installed so my mileage is going to show a bit lower than those without this mod.

The method I use to determine mileage is:

1. Record the mileage from the digital readout
2. Record the odometer reading when filling
3. Record the amount of gas used to fill (always to bottom of neck, with bike on center stand)
4. Calculate miles driven from last fill
5. Divide the number of miles driven by the amount of gas
6. Results generated are miles/gal calculated and indicated (from the digital readout)

I’ll be posting a new thread eventually about the results I’ve been keeping. I understand that everyone’s mileage will vary depending on a lot of factors. I think the data is more interesting in how it changes for me as I do maintenance or as the bike ages.

Hope you find out what’s happening Bryan, and that you get back to normal soon.