• Welcome Guest! If you are already a member of the BMW MOA, please log in to the forum in the upper right hand corner of this page. Check "Remember Me?" if you wish to stay logged in.

    We hope you enjoy the excellent technical knowledge, event information and discussions that the BMWMOA forum provides. Why not take the time to join the club, so you can enjoy posting on the forum, the club magazine, and all of the discounts and benefits the BMWMOA offers?

    Want to read the MOA monthly magazine for free? Take a 3-month test ride of the magazine; check here for details.

  • NOTE. Some content will be hidden from you. If you want to view all content, you must register for the forum if you are not a member, or if a member, you must be logged in.

Why am I getting only 25mpg?

wineguyd

WineGuyD
I have a 1996 R1100R that I recently purchased with 17,000 miles on it. Took it to the nearest BMW service shop and had them do a combined 16/24k maintenance that included replacing all fluids, all filters, the plugs, the ribbed V-belt. They synced the TB and tuned and adjusted everything and anything possible. Conti Road Attacks are new with about 1k miles on them, wheels are balanced and true. Brakes in great shape with lots of life left on pads. I've been using 91-93 octane gas. And finally the bike has the stock OEM windscreen.

In theory the bike should be running in top form now, the specs say I should get an average of 45mpg. When I first got it I went through three tanks of gas and averaged low 30's per gallon, Fuelly.com shows people getting no less than 35mpg and as much as 50mpg. With the bike back and tuned I've done two tanks and averaged 25mpg per tank.

Any ideas as to why such low numbers? I commute on the bike so it gets mixed highway and city riding and I'm not a racer, nor do I gun it or rev it high. I plan to take it back to the shop but I'd like to be as informed as possible beforehand so if they try to blow it off I can respond to them.
 
That's really low.

What coding plug is installed?
Do you have any add-ons like a Power Commander or Techlusion?
RB
 
That's really low.

What coding plug is installed?
Do you have any add-ons like a Power Commander or Techlusion?
RB

By "Coding plug" do you mean spark plugs? BMW installed what ever they considered OEM stock.

No add-ons.

The bike seems to runs smooth, no missing or stalling. Starts up easy. I'm clueless as how this bike should feel and run since I've only owned Honda 4's previously. My first boxer.
 
Here we go, this will be an awesome thread to follow. With all the "experts" to way in, I can't wait to see how far astray they will take you. :thumb
 
25 is just a bit low...

My RT still gets 30 if I run 90-110mph all day. Which it will happily do. Until I get caught.

Aerodynamics on any bike are about the same, which is to say "bad" - windscreen changes have precious little impact.
ditto tires - if you were running them soft enough to impact mpg they would self-destruct in short order.

If it is running very nicely with no low speed complaints I would venture to say you are missing your coding plug.
Or, your O2 sensor is actually bad or unplugged. (if unplugged for very long it might get damaged, so same thing really)

With your religiously OEM, low mileage, unmodified status - I'd actually lean toward a bad O2 sensor.
Rare but certainly possible given the age of the bike.

I know they are a little on the spendy side so if someone knows how to test it?

What either of these conditions will do is force the fueling logic out of closed loop mode.
In closed loop it uses the O2 sensor to detect unused oxygen entering the catalytic converter.
The ECU leans the fuel ratio out until there is some unused oxygen, which ensures that the converter can complete the combustion process.

Also considering the age of the bike, please consider replacing your brake hoses.

p.s. Man that's a good lookin' bike.
 
Last edited:
25 is just a bit low...

My RT still gets 30 if I run 90-110mph all day. Which it will happily do. Until I get caught.

Aerodynamics on any bike are about the same, which is to say "bad" - windscreen changes have precious little impact.
ditto tires - if you were running them soft enough to impact mpg they would self-destruct in short order.

If it is running very nicely with no low speed complaints I would venture to say you are missing your coding plug.
Or, your O2 sensor is actually bad or unplugged. (if unplugged for very long it might get damaged, so same thing really)

With your religiously OEM, low mileage, unmodified status - I'd actually lean toward a bad O2 sensor.
Rare but certainly possible given the age of the bike.

I know they are a little on the spendy side so if someone knows how to test it?

What either of these conditions will do is force the fueling logic out of closed loop mode.
In closed loop it uses the O2 sensor to detect unused oxygen entering the catalytic converter.
The ECU leans the fuel ratio out until there is some unused oxygen, which ensures that the converter can complete the combustion process.

Also considering the age of the bike, please consider replacing your brake hoses.

Thanks Scott..All great points! I definitely plan to bring up the coding plug and O2 sensor in the conversation. As I mentioned earlier, I don't race the bike and have never passed 75mph(true mph, not speedo reading).
 
I have owned 5 different Oil heads and the only time I experienced MPG that low was when my TPS needed to be reset due to being bumped by my leg or foot. Oh ya, there was one other time, when I forgot to put the caps back on the TB's after a TB sync:laugh

No question something is wrong. My guess is that it will be a simple fix...... once you find the problem.
 
By "Coding plug" do you mean spark plugs? BMW installed what ever they considered OEM stock.

Not spark plugs. He's referring to the Cat Code Plug. You can Google that and find some info about where it is located and that if removed, it can cause significantly lower gas mileage. I don't have any personal experience with it so I'll leave it at that. Maybe someone more knowledgeable will come along and provide more info specific to your bike.

By the way, you'll find some good technical info about oilheads on IBMWR's Oilhead Tech Articles page. My favorite resource there is the R11xx Tune Up Manual.

Good luck and enjoy the ride!
 
25 is just a bit low...

My RT still gets 30 if I run 90-110mph all day. Which it will happily do. Until I get caught.

Aerodynamics on any bike are about the same, which is to say "bad" - windscreen changes have precious little impact.
ditto tires - if you were running them soft enough to impact mpg they would self-destruct in short order.

If it is running very nicely with no low speed complaints I would venture to say you are missing your coding plug.
Or, your O2 sensor is actually bad or unplugged. (if unplugged for very long it might get damaged, so same thing really)

With your religiously OEM, low mileage, unmodified status - I'd actually lean toward a bad O2 sensor.
Rare but certainly possible given the age of the bike.

I know they are a little on the spendy side so if someone knows how to test it?

What either of these conditions will do is force the fueling logic out of closed loop mode.
In closed loop it uses the O2 sensor to detect unused oxygen entering the catalytic converter.
The ECU leans the fuel ratio out until there is some unused oxygen, which ensures that the converter can complete the combustion process.

Also considering the age of the bike, please consider replacing your brake hoses.

p.s. Man that's a good lookin' bike.

I'm thinking like Scott, either no plug or a bad O2 sensor.

The coding plug is located normally in the white socket in the photo below.

6aBR6gdh.jpg
 
I'm thinking like Scott, either no plug or a bad O2 sensor.

The coding plug is located normally in the white socket in the photo below.

6aBR6gdh.jpg

Rad, MarkM, Roger...thank you so much for the valuable info. I used to tinker many years ago on my bikes but right now this is an issue I'm going to have BMW fix...whether for free(for overlooking it in the tuneup) or paid. The bike is covered right now due to rain but tomorrow morning I'll check to see if a code plug is present. If missing, are these plug and play if I order one? Are they expensive?
 
Rad, MarkM, Roger...thank you so much for the valuable info. I used to tinker many years ago on my bikes but right now this is an issue I'm going to have BMW fix...whether for free(for overlooking it in the tuneup) or paid. The bike is covered right now due to rain but tomorrow morning I'll check to see if a code plug is present. If missing, are these plug and play if I order one? Are they expensive?

You need a yellow one - something like $6 at beemer boneyard, translates to what, $65 at the dealer?
It will only plug in one way.
Even at $6 I would discourage you from peeking inside it. It is just a jumper.

I doubt they gave the plug a thought doing a tune-up.
 
Bad odometer??
Fuel leak?

There's no smell of fuel nor are there any stains on the ground where it's parked, so most likely not the culprit.

However, the odometer it a thought. Since we know the BMW speedos are always way off, mine shows almost 10mph higher than actual speed when I'm on the highway...so 75mph is actually closer to 65mph, which means the odometer would be rounding up by at least 10-15%. That means that if the odometer shows 100 miles for four gallons used then in reality it was 90 miles and then my 25mpg becomes more like 21-23mpg.

Bad to worse!
 
flars has a good diagnostic thought there though.

Right. My speedo is wildly optimistic, getting worse as the needle moves further into death-defying numbers.
But as you say the odo and speedo in 1990's are driven by the same cable, both should be off the same direction.

Or the odo could be independently broken and just not ticking over when it should.
Do you have a GPS?

A fuel leak is definitely worth checking out. You should smell it, but, you know, you might not, and on a hot day it may never reach the ground.

The real reason for my call is to mention that there are two other sensors that can fail and force the motronic out of closed loop - there is an air temperature sensor poked into the middle of the air filter, and there is an oil temperature sensor. The shop should be able to read the diagnostic codes (after a warm-up) directly pointing to these.
 
Fuel cap?

A thought occurs. My fuel cap hadn't set properly one tank Andover the course of sitting a couple of days I only got 110 miles out of the tank instead do 200. Seals not fitting on the fuel cover would be similar.
 
..... Since we know the BMW speedos are always way off, mine shows almost 10mph higher than actual speed when I'm on the highway...so 75mph is actually closer to 65mph, which means the odometer would be rounding up by at least 10-15%. .....
Bad to worse!

BMW moto speedometers are usually optimistic (not the authority speedos). However, the odometers are usually accurate. Simple enough to check against a GPS or against an interstate highway run with mile markers. Some tires, not OEM, could have a slightly different circumference which could cause a slight variance in the odometer.
 
Back
Top