Quote from: burning1 on June 29, 2010, 03:27:55 PM
Cookie and Andrew:

Most modern cars and a few modern bikes will see improved fuel economy on premium fuels - this is not specifically because the premium fuels produce more power, but instead because the vehicles are equipped with knock sensors, which will detune the engine somewhat when lower grade fuels are used. The knock sensor will retard ignition timing and change the fueling to protect the engine, and permit it to run the low test stuff safely (my BMW K1300GT is equipped with a Knock sensor. The manual states that '89 octane' ron+mon/2 fuel should be used, but that 87 octane may be used with reduced fuel economy and power.)

On a bike like the GS, running a grade of fuel higher than necessary will not result in more power or better fuel economy.

Yes.........

But when I hear a blanket statement that higher octane give better mileage, I wonder.........You have to look at the SMALL details.......

Essentially a car with knock sensors is DESIGNED to run on higher octane in the first place........so we could say the regular DEGRADES the performance/economy.........

Older cars which were designed around higher octane, (without knock sensors) would be severely degraded if regular gas was used........

I will repete again, that an engine designed for regular, will not benefit from higher octane......just wast of money...

I had a car which specified to NOT USE higher octane than regular under any circumstances......not sure why, but I figure the computer was calibrated to regular and higher octane would screw it up...


But for the bigger picture, I sold a 70 MPG scooter, and a 80 MPG 250cc motorcycle to buy my GS 500......I commute by bike almost every day it does not rain.......50 miles a day on week days, and 180 miles each Saturday  and Sunday.........So mileage does matter to me!

I was worried that I was going to get only about 50 MPG.......I was delightfully surprised to see MPG in the high 60's.....

ON REGULAR GAS with 10% Ethanol to boot!!!!!!!!!

We see that our racer friend can degrade the mileage on a stock GS 500 engine to about 13 MPG, and I can get 70 if I drive smoothly...........That shows what driving style has to do with mileage......

Now If I switch to high octane, what will I get?  71 MPG?  Not worth it!



Cookie

Alcohol flat suxs for engines that are not designed for it. I have bantered this on this site before and there are those who defend it. It has cost me over a grand for my boat and bike since it's adoption by the state of Florida a couple of years ago and nearly cost me a Sthil weedeater today but the gas was so bad that my son couldn't run the thing.

My 2005 F gets typically gets right around 60mpg, 90% highway mileage, averaging 70-75mph indicated, with nothing but E10 fuel. I have gotten as low as 39mpg when really flogging it. I've also gotten as high as 73mpg when I took it really easy.

The testing I have read has been on injection car's 

My only fall back is this:

"CHEAP GAS MAKES MATTERS WORSE
To save a few pennies per gallon and to increase the competitive and/or profit margin of gasoline, some suppliers have cut back on the amount of detergent they add to their fuel or have switched to cheaper and less effective additives.

Commonly used deposit-control additives include polysibutylamine, polyisbutylene succinimide and polyisobutylene phenylamine. But these same additives also can build up on intake valve stems causing them to stick. To prevent this from happening, additional additives called "fluidizers" must also be added to the fuel. But, over time, these can contribute to the formation of combustion chamber deposits that raise compression and the engine's octane requirements."

I will avoid supermarket fuel from now on but I may try regular fuel but from Shell/BP...

Thanks for the info though, you lot know your stuff! 

Quote from: lilwoody on June 29, 2010, 07:12:16 PM
Alcohol flat suxs for engines that are not designed for it. I have bantered this on this site before and there are those who defend it. It has cost me over a grand for my boat and bike since it's adoption by the state of Florida a couple of years ago and nearly cost me a Sthil weedeater today but the gas was so bad that my son couldn't run the thing.

This is what happens when politicians try to do the work of engineers............

Cookie

Quote from: Eric_in_OR on June 29, 2010, 08:13:36 PM
My 2005 F gets typically gets right around 60mpg, 90% highway mileage, averaging 70-75mph indicated, with nothing but E10 fuel. I have gotten as low as 39mpg when really flogging it. I've also gotten as high as 73mpg when I took it really easy.

Again a good example of driving style making the greatest difference........75 is pretty fast, so lots of aero drag.....60 MPG is pretty good for that speed..............It makes sense that I get 68 MPG at steady 50~55

Flogging it brings it down a lot!

THe manufacturer claims something like 56 MPG..........consertive estimate!

Cookie

sadly on my '99 I get an avg of 43mpg, mainly in city riding and hills.....curse you SF.... In the mornings, I always have to use full choke to get it running b/c it'd be way too cold outside.  I guess if I commuted on highways, I could probably get more.  As for octane,  I've used 87 and 89 and couldn't really tell a difference between the two, but I did realize that I get better mileage using 76 Gas compared to Chevron.

The Suzuki gas milage figure is based on the EPA emission test for city driving.  YOUR MILAGE MAY VARY.     I find this to be good info for comparing bikes since my overall year around gas milage for my 02 GS runs about 60 mpg, a little better in the summer and a little worse in the winter.  Even thrashing it hard in the mountain twisties it rarely drops below 50 mpg, same for high speed Interstate travel.

My gas milage was a wee bit better on my old 97 GS with 2 circuit carbs and I was riding a lot with a conservative cruiser friend a few years back and it seemed to be close to 70 mpg most of the time so I decided to go for 300 miles before filling up one day and made it, keep in mind it only had a 4.5 gal tank unlike the current 5.3 gal ones.  Never touched the carbs on either and now have 80k miles on the 02 equalling the 80k I put on the 97.  The 97 could have used rejetting but the 3 circuit 02 carbs don't need it in my opinion.

Front tire size can affect indicated mpg since the odometer is driven from the front wheel.

I get between 50-60 mpg. It just depends on my mix of interstate vs in town riding.

Cookie,

I agree with you completely on principal, and I think you're spot on... It's not the premium gasoline that makes the car go further, it's the advanced tuning. Anyone who drives a lesser tuned vehicle or a motorcycle without a knock sensor should keep that in mind.

Conversely, we need to keep in mind that in practice, higher grade fuels may improve power and fuel economy in some cars.

Also, for what it's worth, my street bike is a BMW K1300GT. I'm hard on the throttle. In the city it gets 35MPG, and on the freeway I usually get 42 or so. But, if I take it easy and pay attention to fuel economy, it is quite capable of getting 50 miles per gallon at freeway speeds.

Aerodynamics and gearing can have a huge impact on fuel consumption.