Leaded vs Unleaded fuel??

[Vloukole]

Can anybody tell me what the difference will be when I use leaded fuel vs unleaded fuel in my 81 GS1000 G on performance and overall condition of engine?

The PO told me to use lead replacement petrol. I read now for the first time that the manual states that I should use unleaded fuel. Should I go for 95 octane(best) or 93 octane?

[JTGS850GL]

Manual says 85-95 octane unleaded. I use 87 octane unleaded.

[8ball]

Any vehicle built after 1974 should be made for unleaded fuel. Vehicles built before that had softer valve seats and used the lead as a "lubricant". The GS line wasn't introduced until AFTER the switch to unleaded fuel, so you should be using unleaded. As far as Octane, that is a very misunderstood topic. Higher Octane doesn't mean "better". It means more resistant to pre-ignition, or "knock". A higher Octane fuel will actually burn slower and have less energy. The general rule is to use the LOWEST octane fuel you can without getting engine "knock" or "ping".

ere is some more informative info from a bulletin from Rocket Brand Racing Fuels. But the info is general to all gas engines:

The following is a list of the most significant items that contribute to Octane Rating (OR). These must be kept in mind when thinking about engine OR.

1. Compression Ratio...Higher requires more octane
2. Cylinder bore...Bigger bore requires more octane
3. Cast iron heads...Needs moreoctane then aluminum heads
4. Restrictor plates...Less restriction requires more octane
5. Lean mixtures...Need more octane
6. Coolant temperature...Higher needs more octane; 160 ? is ideal
7. Spark advance...More spark advance requires more octane
8. Intake air temperature...High temperature needs more octane
9. Humidity...dry air (low humidity) requires more octane
10. Barometric Pressure...Higher needs more octane
11. Altitude...Closer to sea level needs more octane

The above information is a guide as to which way the engine octane demand will go as these eleven key parameters are changed. There are other things that impact engine octane requirement, but those listed above are the most significant.

[Vloukole]

Thanx guys, 93 unleaded it is.
Now I know. Thanx 8ball

[JTGS850GL]

Is 93 the lowest octane you can get? Wow, I wish that was the case here. But then again we're paying $1.93/gallon now so I guess I can't complain.

[hampshirehog]

Is 93 the lowest octane you can get? Wow, I wish that was the case here. But then again we're paying $1.93/gallon now so I guess I can't complain.

You guys have a different octane rating system to pretty much everywhere else; I think you label the same stuff 5 or 6 points lower than us so it's pretty much the same thing. Except our gallons are a bit bigger.

[JTGS850GL]

You guys have a different octane rating system to pretty much everywhere else; I think you label the same stuff 5 or 6 points lower than us so it's pretty much the same thing. Except our gallons are a bit bigger.

Got it. Just did a quick check and found that a 4-6 point difference based on RON, MON and the US (R+M)/2. So that would make our 93 octane gas about a 97+ octane. Don't feel so bad now.

[Vloukole]

Yes thats the lowest I can get. We pay R11.30/L. Thats $1/L.
So your 87 octane is our 93 octane?