I always use the premium gas when I fill up. But recently, I filled up at the 97/Spall Cheveron for the first time. I noticed they have four grades of fuel = Reg., Prem., Super Prem., and then the Super Duper Kick Ass Premium. That day I filled up with the Super Duper Kick Ass fuel for 1.42/lt (a little pricey). However, on that tank of gas I went 25 more kilometers before hitting my reserve than using any other fuel! Was this a fluke?

Hmm you sure it wasn't 87 regular, 89 mid-grade, 91 premium, and 94 umm more premium? Yeah it's totally a fluke. Although my car that's designed to run on premium and will retard timing on regular (slower lol) gets terrible mileage on premium. Mainly because I'm going holy crap I have power again and my right foot gets frisky with the floor.

Maybe you filled it further up the filler neck?

WEIRD

WERD.

I don't know much about this, so anyone who does should correct me right away, but as I understand it, octane is really a measure of the "anti-knock" properties of fuel. Higher octane ratings mean more resistance to detonation (knocking), which is the air-fuel mixture in the cylinder igniting prematurely, as in before the spark plug fires. Detonation is common in older engines, which are more likely to have carbon deposits in them which heat up and ignite the mixture, or in high compression engines. Basically, if your motor is not really old (or heavily modified) and the manual doesn't insist that you use premium gas, you don't need to.

Of course we all use premium anyway, 'cause we want to baby our bikes, but it's irrational. And the Chevron 94 octane is overkill for pretty much everyone.

Ok everybody, flame on!

Octane is a fuel's resistance to ignite. The higher the octane rating, the more difficult it is to light. Most all sportbikes produced in the last 15 years have high enough compression where they should be run on premium.

It's not a fluke that you got better mileage. And 94 octane is great for tuned cars/bikes. When I had a nitrous kit in a GTi, I only used 94 octane. Also, it had a compression ratio of 10:1, which isn't huge, but worth running premium for.

Couldn't have said it better myself. That's pretty much it in a nutshell twinman.

If you are using any octane over what your engine is required to use you're simply wasting your money.

I beg to differ. 10:1 in a car is pretty high compression.

The 16V GTi I have now has 10.5 or 11:1. Gives you solid bottom end torque, but you HAVE to use 91.

That's still pretty high for a production street car. Higher compression is not ideal for emissions.

Yeah I guess so. I talked to this old school muscle car guy, and he said back in the day 11+:1 compression was not uncommon, since the leaded gas had higher octane ratings.

Back in the early 70's, the EPA mandated tailpipe emissions and the one of the ways for manufacturers to meet these emissions was to cut compression (higher compression creates more power, but is more difficult to completely burn all of the fuel in the cylinder). As fuel injection ECUs become more and more advanced, it's become easier to control tailpipe emissions. But now the emission standards are being tightened even further so the trick is to meet 2008 emission standards with out losing power.

Hmm funny my old Volvo has a 16 valve 2.3l with 10:1 compression. I already blabbed about it's story. I have to say though I'm glad people are a little more open to good discussion on this topic than other sites (cough bcspor....). I agree that most bikes are high enough compression that you should use premium especially if it says you should. Even my dad's 1100 silverado classic (god I love cruiser names) has a carburetted lump of a motor that's been around for a very long time and it runs much better on premium. Heck even my old 69 volvo 145s wagon with dual su hi6 carbs runs better on premium.

Running better and more power do not = better mileage though. (yes we could get into stuff like more power means you'd have your foot less in it and use less gas blah balh).

I recently saw an article on late model 600s, (I think they were 2007's) where they said the Honda, Kawi and Yami required premium gas, but the Suzuki used regular. The Suzuki rep told them that running premium in the GSXR would cost about one HP. That jives with some other stuff I've read about premium being not quite as energy dense as regular.

Seems like fuel type is a design parameter for engineers. Perhaps Suzuki's decision to design around regular fuel explains the Gixxer's slight lack of power compared to the others.