Modern Vespa

For many years I had an ET4 and I am just a few months shy of two years with my GTS. A few months back I was told to switch to 89 from my dealer and when I mentioned that here it seemed to generate a lot of debate and made me feel like I was doing the wrong thing and that I was following bad advice. I have used 89 for last few months with zero issues. Ride every day. Check out this video that came cross my feed…….if this guy, who is like the scooter guru of all guru, is using regular gas - it must be just fine.

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The user manual for a GTS300 says 95RON which is 91US*. Less may work for you but I prefer to stay with the manual


* http://www.pencilgeek.org/2009/05/octane-rating-conversions.html

According to the American Petroleum Institute (whoever they are) the gas-pump hose typically retains about one third of a gallon of fuel. So when you're only getting 1.2 gallons of 91, 25% of that is 87. Not much, but potentially enough to render it kinda pointless.

And FWIW, 89 octane at the pump is not regular. The pump supposedly blends 89 octane by mixing 87 octane and 92 octane - further splitting hairs as far as what you are actually using.

Just a question out of curiosity.

In Europe 2 versions of gasoline are offered:
- RON 95 (E10)
- RON 98 (E5)

On the video I see 3 versions of gasoline:
- 87 -> corresponds to RON 91
- 89 -> corresponds to RON 93
- 91 -> corresponds to RON 95

So is there no 93 at the pump (corresponding to RON 98)?

I'm at 5,000 feet. I use 87 Ethanol free from a dedicated pump in everything I own. My 1991 Ford Ranger will sit for weeks on end without use. It sits outside and will fire up without hesitation.

I live at 5000 plus feet of elevation,
Carbed bikes run lean at higher elevation & are pickier about octane
If it doesn't knock or run hot the lower octane is fine, manufacturers always suggest fuel with a higher octane than necessary, just to be safe & shift potential liability away from them. If asked by the service department what octane fuel you are using, always answer with their fuel recommendation...

Guys... it's accepted that you can put anything from a gas pump into these bikes, and they should run just fine. We go to Mexico, using Pemex and other garbage fuels along the way. The bikes always run fine. What is the advantage of a higher octane? If you plan on keeping the bike for many years and many miles, then the engine will definitely do better, in the long haul, with better fuel. But if ya wanna save .50 cents on a fill up, your local 87 will do just fine. Don't over think it. Robot is literally over my shoulder, grinning at this response. He's glad he's seen as a guru of all things Vespa! TC

There's a "discussion" going on locally about the same issue here in New Zealand. Now, we use RON, not MON so our numbers are higher. One of our Auckland members is on a bit of a roadie and had found himself only able to buy 91 octane (American 87 I guess). He asked the reasonable question about whether this is okay. The informed, knowledgeable answers have come back as go for it. One tank load isn't going to kill your engine. The opinions are along the lines of "you don't need no stinking higher octane stuff".
My personal experience has been that regular use of 98 or 100 octane fuel improves the fuel consumption over even 95 octane. 91 is mainly specified in NZ in cars of Japanese, Chinese and Korean origin and no doubt many well paid and highly qualified people have engineered the engines to run entirely properly on that. Similarly for vehicles that specify 95 as a minimum, highly trained and well paid people are putting their nuts on the line by telling us this stuff. 98 and 100 octane aren't universally available, but I try to use 98 if at all possible. My choice, as even if there's a 20c/litre premium, $1.50 per fill ain't going to break the bank.

But you have just made an excellent point. Very few of us who own a GTS 300 regard it as a "use it and lose it" scooter. Many years and many miles is exactly what most of us have in mind.

long haul matters.

saving a few cents does not.

so a no brainer to me to follow the manual.

You've got that backwards. Carbureted engines tend to run richer at higher elevations. At 5000' the oxygen density is lower than at sea level. So you are mixing less oxygen with your fuel, yielding a richer mixture.

When I moved from Phoenix (1,200ft) to Sparks (4,550ft) I started fouling spark plugs (too rich). I dropped my low and high speed jets one size each which resolved the issue.

I think I'll spend the extra .50 cents. I'm hoping to keep my new GTS for quite a while. Besides, I get all my fuel at a local truck stop...and they're pretty gosh darned cheap to begin with!

Victor

In Canada, and from what I've seen of the US (NY, PA, OH), some pumps will also have 93, but not most.

Here specifically (Toronto), pumps in more affluent areas might have 93, or areas where people are getting on to or off of the highways you might find 93... Inner city areas in less affluent neighbourhoods, you can pretty much bet they will not offer 93.

It weirded me out when I got to Italy and my only choices were RON95 and diesel.

Robots function exclusively on artificial intelligence which, as we all know, can be a little "off" sometimes, so please keep that in mind.

Kidding aside, what is the actual mechanism that makes your engine last longer when using the higher octane stuff? Or, what makes it wear out faster with the lower octane stuff? What actually happens?

Overly simplifying it until someone smarter comes along, but...

Better detonation.

Some vehicles have higher compression ratios (or turbos, or advanced ignition timing) and they need higher octane fuel.

If they don't get it, there will be knocking, or premature detonation.

No one likes premature detonations, just ask (insert your enemy's name)'s wife.

tech tip

when riding with others let them fill first using premium.

also look at the pumps and see what was last pumped.

Or go to stations that spend the bucks and have separate lines for each octane level.
Kwik Trip here in WI is great for that.

not always possible when traveling,

Don't get fuel here

Sheesh.

As long as you don't put diesel in, you'll be fine.

In the UK, the cheapest is 95RON == 91 (R+M)/2. Merkins have lower octane gas on the whole, mainly I suspect because there are so many good old Amerkin iron engines still around. That said, our gas (petrol) cars have always survived just fine with 87(R+M)/2 .

The scooters get the 91 (mumble formula) because when you're filling up with only 1.6 US gallons the price difference is SFA, so why not...

feel the same, folks spend thousands of dollars on the machine and then bitch about 60 cents higher fuel cost. they should just park it then IMO.

what's else are they going to sing on for maintenance on the scooter?

Like putting plain old air in the tires instead of quality, pure, nitrogen?

Wait: you have a gas station called Merkins? I'd love to see the logo.

We all hate knocking, pinging and pinking but what actually happens to which components to make your bike die young? I can just look it up, but I trust you guys. For some reason.

Premature detonation is when the air/fuel mixture explodes before the piston hits the top of its stroke. So it's not only compressing the air/fuel mixture, it's also fighting the explosion that's *trying* to happen at the same time.

I was told the valves get it worst during detonation.

This guy is a National Treasure. It's Robot, the mechanic at Scooterwest in San Diego.

wrong you must change air blends from summer to winter with the season changes.

I wish Al (aviator47) was here.

Well yeah, that's obvious. But not many people realise that city and country air makes a much bigger difference. You want smog in those tyres of yours? Of course you don't.

if you use one of those portable pumps when you in smell range of a pig farm, that will transfer into your tire air and the next time you have a tire changed they will be able to enjoy your present to them

Ima gonna start pumping up my tyres outside KFC from now on. Should make detection of slow leaks a no brainer.

Not arguing with this, but I'm assuming that running "just fine" would mean it's not pinging, and if that's the case, what less than ideal conditions are making it wear out faster?

higher octane fuel burns hotter resulting in more complete combustion and thus a cleaner combustion chamber. it also resists detonation better which wreaks havoc on internal components-- mainly the piston and valves, but everything is subject to some level of damage because of it.

anyway, run 87 or 91, or hell 93 it doesn't matter. it'll run well on all of them. maybe you'll have less carbon build up or combustion scale in the exhaust after 40~50k if you only ran 91 TT fuel, but that's a hard assumption to make.

if you *can* put in 91, it's just good practice. but 87 isn't going to do anything untoward and you can safely run it in all conditions.

So if your scooter were a person, it would run just fine on a diet of pizza, doughnuts, beer, bacon and Spicy Mo's Smoked Gouda Dip (I do so love that stuff...) but it would need serious medical intervention at around age 47. I get it.

I am intrigued!

I have never quite understood why Vespa recommends middle or high grade gas. Every motorcycle/scooter in Honda's line up uses regular and the compression ratios are similar if not higher.

Non ethanol is the only gas I use in my scooter, either 90 or 91 octane. Non ethanol is definitely the only thing to burn in small carbureted engines.