TheSamba.com :: View topic

Mon Aug 05, 2013 6:47 am

So I have been reading a bunch of E10/E85 questions as late, but what about unleaded gas in our older cars. I know older cars that needed leaded need to add an additive but what about Beetles? I have a 71 Super and was wondering if when new it was an unleaded car or not. I think 1971 was when manufacturers where making the switch but I do not have the owner’s manual for my newly acquired Bug. The car was a one owner and when purchased the owner told me the engine was original and has never had a rebuild.

Mon Aug 05, 2013 7:00 am

Print off the owners manual from the TECHNICAL tab here on SAMBA. All VW engines built 67 to present had hardened valve seats and chrome valves so you should be ok. They just don't last as long they would if the lead in gas that lubricates them were still present. The ethanol will attack old fuel lines from before 1985 - so they should be replaced also for fire prevention. That and ethanol that sits for more than about a month absorbs lots of moisture so use an ethanol stabilizer if you don't drive it much or let it sit for long periods.

Mon Aug 05, 2013 7:16 am

If your really worried about it, you could run a tank of av-gas (100LL) once every ten tanks. That will keep the valves leaded. It works for airplanes/helicopters.

Mon Aug 05, 2013 8:09 am

I have a 73 beetle and it says I can run either leaded or a minimum of 91 octane unleaded. I run 93 octane unleaded through mine and have never had a problem.

Mon Aug 05, 2013 10:02 am

Non leaded regualr 87 octane fuel is fine for a pretty much stock engine. Always was and still is.

In the interest of full disclosure, my stock portfolio and my retirement fund are both heavy into those companies' stock that produce gasoline and it really appeciates those who use primium gas even when it is not needed.

Mon Aug 05, 2013 11:36 am

Helirich wrote: If your really worried about it, you could run a tank of av-gas (100LL) once every ten tanks. That will keep the valves leaded. It works for airplanes/helicopters.
Good luck tracking that down...

Mon Aug 05, 2013 11:52 am

We don't need no stinkin' lead!

Period!

Tim

Mon Aug 05, 2013 12:39 pm

91 octane is the minimum octane rating from the factory. Anything lower than that, you're running the engine on bought time and it eventually will overheat. Air cooled engines like to run cool and "91" is the flash point. I used to run 92 octane in mine while I could get it but now every gas station sells only 91 as premium here. Sunoco sells higher octanes but those gas stations are few and far between. Generally the higher octane gas is marketed to people that are racing.

The first owner of my car used to run 110 octane leaded gas in it all the time or whatever was the highest octane available in the 1970s, knowing that higher octane is best for air cooled applications.

Anyway when you run 89 octane, the combustion process burns hotter than that of higher octane (90, 91, 100+ octane) so the engine will run hotter.

Don't take my word for it though all of this information can be researched online and also check the original factory owner's manual for the vehicle.

Mon Aug 05, 2013 12:43 pm

91 Octane was the rating when before they changed the calculations. 91 RON is about the same as 87 in todays gas.

Mon Aug 05, 2013 1:07 pm

vw57drvr wrote: 91 Octane was the rating when before they changed the calculations. 91 RON is about the same as 87 in todays gas.

where can I find information about this? wikipedia says we use AKI? I dont see a comparison from RON to AKI directly though.

Mon Aug 05, 2013 1:26 pm

92 RON = 87-88 AKI
95 RON = 90-91 AKI
98 RON = 93-94 AKI

Wikipedia: "In most countries (including all of Europe and Australia) the "headline" octane that would be shown on the pump is the RON, but in the United States, Canada and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in the US and Canada, would be 91-92 in Europe. However most European pumps deliver 95 (RON) as "regular", equivalent to 90-91 US (R+M)/2, and even deliver 98 (RON) or 100 (RON)."

Mon Aug 05, 2013 1:34 pm

I can't remember if the change to "CLC" from "RON + MON/2 in the octane was done in 1974 or 1976, but here it is in the 1977 owners manual....

Mon Aug 05, 2013 1:36 pm

ok cool I wonder if I need to take my compression ratio into account as well. I didn't build the engine so I'd have to check on that.

thanks

vw57drvr wrote: 92 RON = 87-88 AKI
95 RON = 90-91 AKI
98 RON = 93-94 AKI

Wikipedia: "In most countries (including all of Europe and Australia) the "headline" octane that would be shown on the pump is the RON, but in the United States, Canada and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in the US and Canada, would be 91-92 in Europe. However most European pumps deliver 95 (RON) as "regular", equivalent to 90-91 US (R+M)/2, and even deliver 98 (RON) or 100 (RON)."

Mon Aug 05, 2013 1:39 pm

That is the only deciding factor for Octane. Higher octane fuel will never directly increase performance. It will only resist detonation better, which is critical for high compression engines.

Mon Aug 05, 2013 3:59 pm

WOW! Great info. Thanks. I just wanted to make sure I did not need to add an additive.

Tue Aug 06, 2013 5:05 am

rooket wrote: 91 octane is the minimum octane rating from the factory. Anything lower than that, you're running the engine on bought time and it eventually will overheat. Air cooled engines like to run cool and "91" is the flash point. I used to run 92 octane in mine while I could get it but now every gas station sells only 91 as premium here. Sunoco sells higher octanes but those gas stations are few and far between. Generally the higher octane gas is marketed to people that are racing.

The first owner of my car used to run 110 octane leaded gas in it all the time or whatever was the highest octane available in the 1970s, knowing that higher octane is best for air cooled applications.

Anyway when you run 89 octane, the combustion process burns hotter than that of higher octane (90, 91, 100+ octane) so the engine will run hotter.

Don't take my word for it though all of this information can be researched online and also check the original factory owner's manual for the vehicle.

Sorry Rooket but that's all so completely wrong.

The octane number of a gasoline is simply a number which tells you how good it is in resisting detonation/pinging. It's nothing more than that.

It has absolutely nothing to do with how hot or cold the fuel burns.

You need to read books by Sir Harry Ricardo, Kettering, Midgely and others on detonation/knocking/pinging. They all investigated the properties of fuels in the 1920-30s when engine performance was increasing significantly and the need for better fuels was rapidly increasing.

There is a lengthy article on my web site which explains it in terms of the affect on VW engines if you are interested.
www.vw-resource.com/octane.html

In short, the VW engine has NEVER needed lead int he fuel, but in the days of leaded fuels they handled it just fine. These days - just fill up with the right octane unleaded gasoline, and off you go - no additives needed.

Alcohol fuels are a different matter. Alcohol has a lower energy content than gasoline so a 10% mixture (E10) contains 4% less energy per gallon/litre, so your engine will run lean unless you increase the size of the main jet in the carb. But once again, that fact has nothing to do with the octane number.

Tue Aug 06, 2013 6:32 am

Refreshing,men who understand fuel...Ive yet to see concrete proof of a failure directly attributed to alcohol in gasoline,or the elimination of lead causing a valve failure.I've seen a lot of scammers trying to sell a product to offset these mystical issues,and the fear they use to sell their product..but never the actual failure,where you could put your finger on it and say with absolute conviction heres your alcohol/no lead failure..

Tue Aug 06, 2013 7:24 am

the American cars with the cast iron heads where the seat was just cut into the cast iron and the guide was just a hole drilled thru the cast iron were the ones that needed the lead as a lubricant .... with bronze guides and hardened seats VW already had what others had to upgrade to

Tue Aug 06, 2013 10:25 am

cookrw wrote: Helirich wrote: If your really worried about it, you could run a tank of av-gas (100LL) once every ten tanks. That will keep the valves leaded. It works for airplanes/helicopters.
Good luck tracking that down...

It's at nearest airport.

Tue Aug 06, 2013 10:26 am

Helirich wrote: cookrw wrote: Helirich wrote: If your really worried about it, you could run a tank of av-gas (100LL) once every ten tanks. That will keep the valves leaded. It works for airplanes/helicopters.
Good luck tracking that down...

It's at nearest airport.

I did not think you could walk up with a gas can and get some? You don't have to have a plane with you?