What gas do you use?

[New2Me]

I was just wondering what kind of gas everyone uses in their bike. The PO told me the bikes were made for Leaded gas but his mechanic friend told him to use Premium instead. Is that true? I have been running premium but just wanted to see what others run.

[bikerphil]

It's OK to run regular octane unleaded, but I run the mid-grade. Got my timing advanced a couple of ticks. The super will carbon up the valves, YMMV.

[gareth]

Running zrx1100 carbs on a SF. Did the mod which drills the carb body at the throttle plate to allow the use of the vacuum advance. I was a bit worried that the engine might be running a bit overadvanced so I have been running Plus gas as a precaution. Runs great..

[tw1980]

premium or she pings

[Bonz]

Can't tell a bit of difference between any of the grades in my 80 SG. Running at high elevation, octane requirement is lower, so I run low octane grade with nary a problem. Can't speak to what it would need or run better on at lower elevation, but I suspect when properly tuned in more or less stock form the lowest octane rating would be fine, higher octane would be just for show.

Question: How does "super" carbon up the valves? I assume that is referring to "super" as the high grade.

[3Phase]

Question: How does "super" carbon up the valves? I assume that is referring to "super" as the high grade.

Premium gasoline burns slower.

The fuel charge is ignited exactly when it should be for a lower octane gasoline but it doesn't finish burning before the exhaust valve opens.

Peak combustion chamber temperature and pressure is lower and there is still some unburned fuel left over at the end of the power stroke so carbon can form and build up.

The still-burning fuel goes out the exhaust valve into the exhaust manifold and finishes burning on the way to the muffler so exhaust temperature will go up.

[fredintoon]

I use regular gas because I've never noticed any difference when I've used premium.
I try to buy gas from co-op because I get a divi on it.

[James England]

In the era of the XS1100, just about all Japanese cars and bikes were meant to run on unleaded fuel. They were ahead of the rest of the world on emissions control at that time. Valve seats were hardened etc and their vehicles were generally designed to run on unleaded. I've run every Japanese bike I've ever had on unleaded fuel (from when they started supplying it here years ago... prior to that '2 Star' low octane). I lived in Tokyo in 1988 and never saw leaded fuel at all.

I had a 12 year old Toyota Starlet in 1991.... the handbook advised unleaded fuel. At a time when most British cars needed '4 Star'.

[Diskman01]

1978 XS11. Unleaded, 87 Octane (these are LOW compression motors). NON-Ethanol!!!!! No Alky at all in my gas.

If I run the 10% ethanol I notice that my idle drops about 200RPM or so. The "Butt-Dyno (tm)" tells me that ethanol gas is a tad slower around town.

Plain old 87 octane unleaded seems to be fine. It's more expensive here in SD than 90octane with the ethanol, but it runs smoother with plain gas.

[TADracer]

I have tried all grades with both the stock Mikuni carbs and with Keihin carbs from a ZRX 1200 along with combinations of stock plugs and one step hotter. After trying all this, I use regular unleaded and IMHO, never, never put lead substutute into your gasoline on these bikes, no matter what type of carb you are running. Gums up pilot circuits alot more quickly. I have no pinging on the regular and premium does nothing for me so the xtra cost is not warranted. Valve seats work just fine on unleaded.

Now the ethanol thing is something I do not like. I try to find 100% gasoline when I can but when I am forced to use 10% ethanol, performance and mileage drops off slightly. I guess when it becomes the norm and 100% gasoline is no longer available, we will have to tune for the ethanol.

[New2Me]

I think I'll just use regular from now on. Kind of funny I filled up with 93 octane yesterday and added Seafoam to help "clean" the engine. But in reality I think they counter act one another and I'm sure the 93 will win in the end. I dont think it will hurt to treat again on the next tank full of regular.

100% gas must only be available up north because I never see it in my neck of the woods. In fact the only time I see gas without ethanol is when I go to my uncles in Minot, ND.

[BA80]

Actually, when these bikes were produced they were recommended to run regular fuel the only thing is back in 78-82 regular gas was 93 octane. However, there was no ethanol in it like there is pretty much everywhere now.

I've tried todays premium (93oct) and my bike is really sluggish running, reguar (87 oct) runs great but I get that pre ignition thing on the highway, so I'm using the mid grade (89 oct) and it runs just fine so that's what I use unless it's not available where ever I'm at. The it's regular.

[XS1100 Newbie]

I just run regular on my 80LG. never saw any difference running super. All the gas here has ethynol, but mine runs fine.

[neJeff]

Where I am from there is 87 (regular, no ethanol) 89 (super, 10% ethanol) 91 (premium, no ethanol). I buy/use the premium and I buy it at a name station, like Mobil or Shell. Probably does not matter what octane you run but I recommend staying away from Quikie Mart type gas. Stick with branded gas

[Bonz]

Reality is ethanol has been in many gas pumps since the 80's, certainly in 95%+ of Colorado gas for 20+ years. The main concerns, in engines/fuel systems where the fuel sits unused for long periods of time is the affinity of ethanol to attract water. Sta-bil will take care of that, and don't leave lots of airspace in the tank for the ethanol to pull water from, keep it full when storing it.

I would like to have 100% gas, but it is so rare that 10% ethanol is basically all you get. Been running lawnmowers, weed trimmers, motorcycles, cars, etc on the 10% for as long as I've owned 'em.

After 14 years, rebuilt the carb on my lawnmower this spring, had to as it wouldn't start after I ran the first tank of the year through it. Just cleaning the carb didn't do it, so put in a new needle, seat, gaskets, you know the normal stuff. Was it the ethanol, or just plain age?

On my '80 XS SG, had to rebuild the original carbs last fall, o-rings on the float needle seats weren't sealing, dumping gas into the carbs. The XS will be 32 years old next year. Not a speck of anything in the fuel tank, and the fuel screens on the petcocks are spotless. Ethanol or age?

IMHO, the negative mechanical effect of ethanol gas is HIGHLY over stated, unless the bike or other device is stored improperly or otherwise has elements introduced into the fuel system that shouldn't be there anyway, or if the fuel system is in poor repair to begin with.

There was mention of Super grade gasoline being used, and Seafoam being added, and that they counteract each other? How was that conclusion arrived at? In all humbleness, that makes no sense.