Effects of high octane fuel

tachrev wrote: Octane is octane. If you aren't detonating, higher octane won't make more power by itself no matter what the vintage or engine design.

Lead in fuel was an octane booster and a lubricant or sorts.

I'm just saying that in the 70s regular leaded gas was 90 octane, & premium gas was 98-100 octane, so I'm saying our older bikes were built to run on higher octane than 87
Pete

pete greek1 wrote: I'm just saying that in the 70s regular leaded gas was 90 octane, & premium gas was 98-100 octane, so I'm saying our older bikes were built to run on higher octane than 87
Pete

Even though many folks run 87 octane just fine, I tend to agree with you on this. I don't even think 87 octane was even available when my bike was made. Probably the lowest octane in my area back then was 91. I know for sure you could still get 95 and 100 octane in my area. When I bought my KZ650 (April, 1977) the dealer told me to use premium gas. 93 octane is considered premium now; back then it would have been mid-grade at best.

I've read that some folks mention that their manuals call for 87 octane. I would really be interested to know exactly which manuals for which year and model bikes state that. My Owner's Manual does not name a specific octane level. It simply says you should use unleaded gasoline. Ed

My gpz's, just barely get by with 93 on hot summer days. They are only 10:1 compression. I used to use Lucas octane boost, but it's expensive and a hassle, so now I just roll the throttle slower or downshift to get the RPMs up.

Ed, that's interesting that your manual specifies unleaded. I'll see if I can find anything in my owner's manual.

EDIT: it says use 87 minimum, or higher. (That is 87 as we have it in the U.S. (RON+MON )/ 2 .)

Here's all it says about fuel:



The Manual:

I'll double check my manual tonight.

Lou your post confused me. You said your bikes barely get by on 93. Are you saying 95 would be better or lower like 87 would be better?

That is exactly what is in my 77' KZ1000 owner's manual.
And, Since living in Colorado sine late 1978....I have been runny my stock engine with mostly no-lead 85 octane, but I do use 87 in the super heat of summer +85-100 degrees and it really didn't knock with either.
With the 10.25:1 pistons, I have been using 91 Octane.

Just to be clear, using a higher octane fuel than the minimum needed rarely causes problems. It's just a waste of money. Regarding super high octane fuels of bygone days, those fuels had lots of additives which increased engine deposits. It would be nice to still have the option, but not sure some of those fuels were better per say.

apbling wrote: crap.
I was hoping you'd say that the higher octane would have a slower burn, causing the timing to be a little off and not run quite right

Back in the 90's, there was a "rumor" that running premium in Saturn engines could mess up the way the anti knck sensing worked because it burned too slow. I think it's baloney. I don't think burning higher octane fuel can cause any harm, but ethanol sure can..... already had to replace the fuel pressure regulator on my Chevy after about 30,000 miles.

650ed wrote:

pete greek1 wrote: I'm just saying that in the 70s regular leaded gas was 90 octane, & premium gas was 98-100 octane, so I'm saying our older bikes were built to run on higher octane than 87
Pete

Even though many folks run 87 octane just fine, I tend to agree with you on this. I don't even think 87 octane was even available when my bike was made.

Correct. I remember that the lower octane gas was about 91 back then and premium was at least 95 or better. Then for a while 89 was the low octane rating.

It was a BIG time problem because premium was unleaded only and the regular still had lead so anybody with an older "lead only" engine was in trouble if it needed premium. The Mercedes dealers were telling people to mix regular and premium 50-50 in the tank and live with the pinging. I remember my 1970 Plymouth Duster really pinged on 91 gas.

On hot days, if I'm just cruising at around 65, and I start to give too much throttle, it'll start to give me some knocking, which actually sounds more like a rattling noise. I have to let up to prevent that, or just kick it down a gear or two if I really want to accelerate quickly. It is probably partly to do with the mechanical advancer being less than ideal at low to mid RPMs. From what I recall, 20 years ago or so, it was worse with 87. So I use only 93 nowadays. The octane boost seemed to help a little, but I never did any controlled tests.

The standard KZ550 has lower compression, so I assume it's less of a problem.

It's hard for me to say for sure if it's a octane problem, or an advancer problem, in any case it's not a big deal as long as you don't get lazy driving it like an automatic.

The electronic advance systems had a less agressive advance curve, but advanced the entire RPM range.

loudhvx wrote: On hot days, if I'm just cruising at around 65, and I start to give too much throttle, it'll start to give me some knocking, which actually sounds more like a rattling noise. I have to let up to prevent that, or just kick it down a gear or two if I really want to accelerate quickly. It is probably partly to do with the mechanical advancer being less than ideal at low to mid RPMs. From what I recall, 20 years ago or so, it was worse with 87. So I use only 93 nowadays. The octane boost seemed to help a little, but I never did any controlled tests.

The standard KZ550 has lower compression, so I assume it's less of a problem.

It's hard for me to say for sure if it's a octane problem, or an advancer problem, in any case it's not a big deal as long as you don't get lazy driving it like an automatic.

The electronic advance systems had a less agressive advance curve, but advanced the entire RPM range.

My old GPZ550 knocked a good bit, but I think it was caused by lean jetting because it had a header and stock jetting. That was back before I knew better.

Loudhvx can you get hold of Avgas in your area - that should fix your problem - try 20 % in a normal tank and go from there.
Had exactly the same thing in 94 with mine. Pinging like a bastard up hills/under load and getting beaten by farking cars and not doing the motor any favours either - now that just wasnt on - was about $2.50/ Litre 20 years ago - found out the other day it is $4 /Litre now so just a little expensive here. Normally alternate between 95 and 98 octane but dont really notice any difference - bike is 9.5: 1 .