Premium gas for 1980 GS1000s

[doctorgonzo]

in many european countries you cant buy anything less than 95 octane gas, and this has been so for a number of years now
reading this thread it would follow that their gs bikes run very poorly and suffer lower performance
any thoughts?

.

A well maintained engine with good compression, hot spark, and properly jetted carbs can probably handle that higher octane and still get a complete burn with no problem. Also, they wouldn't have the other issue we have in the US with premium (93) octane gas, which is very few people buy it, so it sits in the tank at the station for months instead of being regularly cycled out from sales. A few guys with sports cars, a few rich old people, and motorcycle riders are the only people who buy it. They sell regular at 100X the rate.

[hampshirehog]

in many european countries you cant buy anything less than 95 octane gas, and this has been so for a number of years now
reading this thread it would follow that their gs bikes run very poorly and suffer lower performance
any thoughts?.

All it means is that we are paying more for better refined petrol (higher octane percentage, lower heptane percentage) when we don't need to. (Heptane doesn't compress very well and can spontaneously ignite under compression).

However, if I want to crank my bike up, say with a Wiseco high compession kit, I can stay running the same fuel.

[psyguy]

All it means is that we are paying more for better refined petrol (higher octane percentage, lower heptane percentage) when we don't need to.

from what i'm reading here it seems that you also risk incomplete combustion and more deposits inside the cylinders

that said (dont know for uk, but) many european countries didnt have petrol with less than 91 octane for 30years now, that means that back then new GSs would start their life using 91 octane petrol, as that was the lowest octane petrol available

surely, japanese manufacturers were aware of this when designing their engines?

[doctorgonzo]

from what i'm reading here it seems that you also risk incomplete combustion and more deposits inside the cylinders

that said (dont know for uk, but) many european countries didnt have petrol with less than 91 octane for 30years now, that means that back then new GSs would start their life using 91 octane petrol, as that was the lowest octane petrol available

surely, japanese manufacturers were aware of this when designing their engines?

They were, my manual isn't handy, but I think it says 89 (lowest octane you saw then) through 95. I think the point is, premium probably isn't going to make your bike run bad, especially a well maintained, well tuned one with good compression, BUT it can exacerbate low compression and/or weak spark and make their symptoms even worse, plus the old gas problem in the US, and the fact you're paying for high octane you likely don't need. If you aren't getting pre-ignition or detonation, just no reason to spend the extra $.30 or $.40 a gallon (in the US)

[psyguy]

thanks doc

this sums up the discussion for me nicely

btw, in nz 91 is the lowest available petrol and thats what ive been using

cheers

They were, my manual isn't handy, but I think it says 89 (lowest octane you saw then) through 95. I think the point is, premium probably isn't going to make your bike run bad, especially a well maintained, well tuned one with good compression, BUT it can exacerbate low compression and/or weak spark and make their symptoms even worse, plus the old gas problem in the US, and the fact you're paying for high octane you likely don't need. If you aren't getting pre-ignition or detonation, just no reason to spend the extra $.30 or $.40 a gallon (in the US)

[Steve]

in many european countries you cant buy anything less than 95 octane gas, and this has been so for a number of years now
reading this thread it would follow that their gs bikes run very poorly and suffer lower performance
any thoughts?

.

My thought on this matter is that if you read the pump (in the US), you will see that the posted octane number is an average of the Research Method and the Motor Method. I think that the European countries are using the higher number (I don't remember if it's the Research or Motor), not the lower, averaged number that we use.

For those who are in the mountain states of the US, be aware that the lowest octane available might be as low as 85. This is not a problem. With the lower oxygen content in your thinner atmosphere, you get the same combustion effect with 85 octane that we do at the lower elevations with 87. I have been able to use 85 and 86 octane when travelling in the mountains, unless we were heavily loaded and towing a trailer, then I would go to the mid-grade, usually 87 or 88.

.

[Dan Ruddock]

My thought on this matter is that if you read the pump (in the US), you will see that the posted octane number is an average of the Research Method and the Motor Method. I think that the European countries are using the higher number (I don't remember if it's the Research or Motor), not the lower, averaged number that we use.

For those who are in the mountain states of the US, be aware that the lowest octane available might be as low as 85. This is not a problem. With the lower oxygen content in your thinner atmosphere, you get the same combustion effect with 85 octane that we do at the lower elevations with 87. I have been able to use 85 and 86 octane when travelling in the mountains, unless we were heavily loaded and towing a trailer, then I would go to the mid-grade, usually 87 or 88.

.

Best post yet that I have seen yet on this thread. Feeding a motor more octane than it needs is a waist. Dan

[49er]

I'm with Brainbucket and some others on this one!
However, it really depends on whether you are running your bike as a commuter and happy with average performance, or whether you expect a bit more. If it's a commuter, go for the cheap stuff.

On my stock GS850 at 8.8-1 CR, I used to run 91 octane. The compressions were down and ranged from 110-130psi. It performed ok.

The cheapest performance upgrade is to increase the CR. Wiseco appear to limit their road ratios to 10.25-1 and I suspect, for a very good reason. At above this figure, many air cooled motors will suffer pre-ignition/detonation and overheating issues. This is compounded by the usual increase in spark advance. The solution is to run higher octane fuels.

To take advantage of the slower burnoff rate, the motor's state of tune must be quite exact, ie a strong regular spark with ideal ignition advance curve/range, correct spark plug heat range, head chamber shape and squish areas and carbs metering the fuel correctly throughout the entire rev range.

I bought an oil cooler prior to fitting the 10.5-1 pistons to my 850. I was surprised how cool the motor runs on 98. It actually runs cooler than it did in stock trim on 91. I haven't bothered to fit the cooler.
I can run 95 without detonation but it performs better on 98.
I often run 95/98 blends, as 95 is more readily available here on trips.

[GaThumper]

My .02 (probably .03 with inflation)

I have in the past ran premium in my bikes thinking I was treating them to a better fuel and maybe getting better performance. I now believe if it's not required due to engine design and tuning, it's better to run regular.

However the biggest thing to me came when I read (or was told) that with the high price of gas today very few people will run premium (or mid grade) resulting in possible old and contaminated gas sitting in the underground tanks for extended periods of time. Because almost everyone buys regular it's constantly being replentished, so you get fresher gas when you buy regular.

True or not, it's on my mind every time I pull up to the pumps, and I'm too worried about getting "old" gas to even think about which is better any more!

YMMV...
James <><

[Cajun Cycler]

Makes sense to me!

[49er]

Here is some technical info I have found on fuels. It dates back to the era of our bikes and also mentions later engine management systems and fuels.

Section 7 covers many of the questions that have been asked and provides evidence to counter many of the theories being touted on this subject.

http://www.faqs.org/faqs/autos/gasoline-faq/part3/

[Dan Ruddock]

That is a must read for many of you. Dan

[GSJake]

all of my experience with a lot of different types of vehicles and motors says that the higher octane gas the better. i always get better gas milage when i use the 91 octane gas.

[Sandy]

I've always used regular in all my motorcycles. In 39 years and lots of miles I've never had any engine melt downs. Even my ' 85 FZ750 ran great on regular.

[mac1170]

Here is some technical info I have found on fuels. It dates back to the era of our bikes and also mentions later engine management systems and fuels.

Section 7 covers many of the questions that have been asked and provides evidence to counter many of the theories being touted on this subject.

http://www.faqs.org/faqs/autos/gasoline-faq/part3/

gday 49er, that was a good read, note they said older motors with no engine maagement, i once broke a comp ring, because i down changed and gave it a handful, at the exact same moment my rear wheel hit a severe bump, because it failed to select the gear, all i heard was a big knock from the motor , this was on 91 octane, next day i fired her up and i could see this little smoke plume out the exhaust, instant shutdown, slip barrels off, and broken ring, this was on a motor that had done 90,000 kms, regards,