Which Octane for my Beetle?

[JoePalooka77]

Which octane should I use in my 1973 VW Beetle with a stock 1600cc DP type 1
engine? It has 0.020 ring spacers put under the cylinders to help lower
compression for use with the lower quality of today's fuels.
On the fuel filler door it says Use 91RON, so I always thought that meant
when I go to get gas here in the USA, to choose the pump with the yellow label
with the black 91 on it.
Aussiebug e-mailed me and said the 91RON gas is not the same as the 91 pump
gas sold here in the USA. 91 RON is the same as 87 pump gas (USA)
which is figured according to (R + M)/2 or (RON + MON)/2 or
(91RON + MON)/2 = 87 octane pump gas (USA)
(93RON + MON)/2 = 89 pump gas (USA)
(95RON + MON)/2 = 91 pump gas (USA)

I was considering starting off with 91 octane pump gas (USA) in hot weather or
when going on out of town trips.
Around Veteran's Day, when it gets cooler, I was going to try 89 octane pump
gas (USA).
If that works out and everything is running smooth, i was going to try 87
octane pump gas (USA), just to see how that would work.
Then I planned on going back to 89 octane pump gas (USA) for a little extra
anti ping insurance.
What do you think?

[Mike Fritz]

Read this reply to Gary, this will give you an idea, it's not exact, but it'll do.
I no longer say gasoline is of lower quality, it's just been reformulated to run
leaner, or cleaner, in watercooled computer controlled vehicles.

Quote myself ------------------------------------------------------>

The reason anyone would lower the compression is because of the lower octane of
gasoline. The ignition timing should remain stock. Why? Let's look at how
gasoline has changed.

Back in the time of Bugs, the gasoline was leaded, and lead is a great octane
booster. Then came catalytic converters, lead cannot be used, destroys them. So
without lead, the octane was lower. Sometime in the 80s, in the USA, the way
octane was calculated differently, more accuratly, was adopted. This made 91
octane 87, for example. So using 87 is perfectly fine, in a stock VW engine,
with stock compression.

Problem? Reformulated gasoline. This means there is oxygen, alcohol, and such
added. Well, your engine runs on gasoline, and oxygen. Adding oxygen to the
gasoline leans your mixture, oh geez, more problems. And alcohol makes your
engine's combustion hotter, more problems. All this can lead to detonation, NOT
combustion, or pinging, very bad. This leaner gasoline is cleaner, which is
great for water cooled, computer controlled cars, but not for our Bug.

Solution #1? Lower the compression. You loose performance, perhaps your
emissions will suffer, and your mileage. Solution #2? Keep stock octane, and
use higher compression, 92, to compensate for the reformulated gasoline.

You can still use flat pistons, this will give you 7.5:1 compression on the
1600. The dished pistons lower this to 7.3:1. I don't know why VW did this, I
think it was done in 73. Many people try and talk my into using flat pisons
with spacers, but that seems wrong to me. I use spacers to compensate for head
machining. I use the dished pistons because that's what VW used.
Mike

Gary Miller wrote:

> Hello.
>
> On the optional low compression engines, what was different? What is the
> setting for ignition timing on these engines.
>
> Also, along the same lines, what was the difference in the high compression
> (1500s) engines?
>
> I'm guessing dished/ domed pistons here, but would like some reassurance.
>
> Cheers
> Gary

JoePalooka77 wrote:

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[Joe Kovacs]

I'm confused by this too. This is my experience.

The manual for my 88 Nissan Sentra, which I got new, said the
same thing, use 91 RON or 87 AKI octane. Miserable, misleading
thing, the numbers on the pumps are 87 and 91. :-(

Wal, it was OK, because I actually ran premium gas. No doubt the
dealer told me to do that. Early on I tried regular, and the car
started to ping badly at 56 miles per hour, so that was that,
easy as that.

It would ping on 89 at the pump, and run OK with 90.

This was with 100% gasoline. I once caught a rumour that
gasoline with 10% alcohol added is high octane, about 96, that
the delivery tanker trucks put the same gasohol into both the
regular and premium tanks. But, while I often ran premium
gasohol, I never got around to testing that myself. Anybody
know?

I changed the oil twice as often as the manual said to do, and I
did a couple of other things. And with that, I got 470,000 miles
out of that Sentra quite routinely. That car doesn't owe me a
thing! At that point the body had rusted and the engine controls
went bad. The engine itself used a quart of oil in 1000 miles and
it was in good shape.

So I know a couple of things. Therein lies the good reputation
of the Nissan Sentra. And when someone says they changed the
engine on a Sentra at 80,000 miles, we just _know what they've
done, they can't handle the responsibility of driving a car.

To know whether to use regular or premium gas at the pump, you
have to know what pinging sounds like, put the gas in and listen
for pinging. There. That's my experience.

In <20000825140119...@ng-fd1.aol.com>, joepal...@aol.com (JoePalooka77) writes:

> Which octane should I use in my 1973 VW Beetle with a stock 1600cc DP type 1
>engine? It has 0.020 ring spacers put under the cylinders to help lower
>compression for use with the lower quality of today's fuels.
> On the fuel filler door it says Use 91RON, so I always thought that meant
>when I go to get gas here in the USA, to choose the pump with the yellow label
>with the black 91 on it.
> Aussiebug e-mailed me and said the 91RON gas is not the same as the 91 pump
>gas sold here in the USA. 91 RON is the same as 87 pump gas (USA)
>which is figured according to (R + M)/2 or (RON + MON)/2 or
>(91RON + MON)/2 = 87 octane pump gas (USA)
> (93RON + MON)/2 = 89 pump gas (USA)
> (95RON + MON)/2 = 91 pump gas (USA)
>
> I was considering starting off with 91 octane pump gas (USA) in hot weather or
>when going on out of town trips.
> Around Veteran's Day, when it gets cooler, I was going to try 89 octane pump
>gas (USA).
> If that works out and everything is running smooth, i was going to try 87
>octane pump gas (USA), just to see how that would work.
> Then I planned on going back to 89 octane pump gas (USA) for a little extra
>anti ping insurance.
> What do you think?

--
Joe Kovacs
Guelph Ontario Canada

[main]

Take a look at the pumps at the station to see if there is any indication of
use of
gasahol - avoid these stations. The real cheap stations tend to use it
more. If you
can't tell or if it is not marked anywhere, you may have to resort to trial
and error.
I have always had to try a number of brands to get one that works well in
different cars.
Exxon has always caused me problems after a few tanks. Since Mobil/Exxon
got
serious about merging, I have found Mobil no longer is "better". At least
in my area
they seem to've switched to Exxon's formulas ((additives)). Good luck. You
may find
the opposite to be true.

I guess it all depends upon what she (your car) wants - and what makes her
feel important.

NOTE: Higher octane = hotter/slower/more even burn. (hotter isn't "cool"
for VWs....)
Mike Fritz <mwf...@psn.net> wrote in message
news:39A731AE...@psn.net...

[Mike Fritz]

MTBE is used where I've ever lived lately. I think it's only used a certain time
of the year, I'm not sure. Like I'd be able to learn what each company uses, or
should I say, like any of them would "spill the beans". Aren't additives addes
to all pumps due to government regulations? So when is Gasahol used? Why? What
cars does it work better in?
Mike

[KWW]

Used to be that the pumps had to be marked with a sticker when they used
gasahol. It was voluntary, and was considered "ecological". Actually that
was spelled "c h e a p" because, with the Govt. subsidies for gasahol
production,
it came out to be less expensive than gasoline. The cheap stations tended
to
run it. Note, in most states, the Dept of Agriculture is tied in with
weights and
measures, so an "Ag" sticker doesn't necessitate the use of Gasahol. That
just
means that they test the truthfulness of the pump.

If you have fuel injectors gasahol is not cool since the molecular size of
the water
in the alcohol is larger than that of the gasoline. Also, older fuel
systems corroded
because of the water.

"Mike Fritz" <mwf...@psn.net> wrote in message

news:39BAEBC4...@psn.net...

[Nickolas Marple]

Mike,
In the summer season in Maricona County (actually 3/31-10/1), we have MTBE
(Methyl Tertiary Butyl Ether) in the gas.
Ethanol is used during the rest of the year.
These are both oxygenating additives that cut carbon monoxide. My
assumption is that they both do this by increasing the combustion
temperature.

Here's a link with some explanations:
http://www.chevron.com/prodserv/gas_qanda/oxygen.html

--
Peace,
Nickolas Marple
Mesa, AZ
'71 SB, "Scarlet"
volksNO...@yahoo.com
http://www.geocities.com/volks1302

(Please remove NO and SPAM from address to send e-mail!)

"Mike Fritz" <mwf...@psn.net> wrote in message

news:39BAEBC4...@psn.net...

[Nickolas Marple]

That's Maricopa county, not Maricona county. DOH!
Nick

"Nickolas Marple" <volksNO...@yahoo.com> wrote in message
news:Wq6v5.805$96.3...@pouncer.easynews.com...

[Mike Fritz]

I agree, the same is so for San Diego. I would think oxygenated fuels would make
your Bug run leaner, why? Duh, oxygenated gasoline has oxygen. So the gasoline
is leaner itself, I think my Bug suffers lean misfire a lot.
Mike