OK, unfortunately this may have caused the incident. Car fuel can show non-linear pressure build up when heated, as a consequence pressure build up can be almost explosive. If this happens, the SRV of the tank lid is not able to open fast enough and instead the base pops out. This is one reasons why Optimus clearly states not to use car fuel in the 123R. Also, old stoves with old tank lids can have non-viton rubber components that will swell on contact with car fuel, thus causing the SRV to jam.
should change to 91 octane as it has less additives so less blockages. In saying that though I own a Radius 42 that was used without issue for 30 years on leaded fuel
@geeves Go with an additive-free fuel. The names vary around the world. The Americans say "white gas" or "Coleman fuel" while Aussies say "Shellite" and the British use "Naphtha" or "panel wipe". They are all essentially the same stuff, virtually identical to the core ingredients of petrol, but with nothing to stop explosion under pressure. No-one is ever going to get their stove to 10 atmospheres of pressure, so anti-knock additives just clog the works. I hadn't heard of the variable pressure responses with additives before though preventing pressure buildup is hardly what you would aim for in a fuel for an engine with cylinders.
Thank you for this information. I had not heard of it before relevant to car fuel. I will have to look in my reference stuff- I think I have heard of specific additive blends for different high performance aircraft engines. One more reason to stick to white gas in an old stove. Crossing over to old motorcycle restoration, a common trick on unobtainable rubber parts like intake boots, which were often very hardened by age, was to soak them in brake fluid to soften them up. A low pressure application, not at all like a stove, which holds pressure and has to tolerate heat. I can see using this trick, maybe, on orings or rubber washers, but getting modern versions of those is not hard at all.
Optimus instructions (and everyone else) going back decades have little to say except simply referring to Gasoline (petrol) as the fuel. Sometimes, “uncolored” Gasoline. The idea then was to avoided high octane leaded fuel. I’m not aware of any special cautions or warnings e.g. “Coleman Fuel” (which in any event debuted much later) Given the century + long history of gasoline powered appliances there should be no technical issue using unleaded automotive gasoline, with the caveat that unlike Coleman fuel or Naphtha it will spoil or oxidize into a rancid mess after long storage.
This probably depends on how many decades you count. At least since the 1970's/1980's, the instructions of the 123R have clearly stated not to use car fuel, see e.g. here: https://classiccampstoves.com/threads/svea-123r-manual.47109/ Same with 8R https://classiccampstoves.com/threads/1979-optimus-no-8r.272/ Also, the tank of the 123Rhas been stickered since the 70's/80's with a label clearly stating not to use car fuel. Depending on the design of the stove, the danger of the use of car fuel will vary. A self-pressurized stove will be more sensitive to the issue than a stove with a remote tank and pump.
@Fettler And this applies even more to unleaded high(ish) octane gasoline. The "low octane" fuel of the early 20th century was REALLY low octane, well below anything sold today for automobiles. The Australian term for unadulterated gasoline- Shellite- dates from this earlier era. Great marketing by Shell, who still own the name. There was also Mobilite back in the day, and I would guess other "lites". The other side, easily checked, is what the compression ratio in the vehicle is (or was). My old 1960s Land Rover ran about 7:1, which would probably let you run Coleman Fuel (etc) in the tank. Modern cars run 9:1 or higher. No modern car is low enough compression to use the standard fuel referenced in the old stove instructions.
Right, they specifically state to use Unleaded gasoline, or white gasoline. I’m not persuaded “car gas” is a cause for concern, at least not from a safety perspective. Tetraethyl lead has been banned on the road for over 40 years. The sticker on the more modern exemplars says “Use white gas or unleaded petrol only”. Seems reasonably clear to me it should not pose a safety issue.
Wow reading all this makes me feel like I ran my 123 not very responsible all these years. I always run mine on 87 octane gas and it runs great, never had any problems. Now one thing I did do with the stove a few years ago that I would never do again after seeing this post is putting one of those stove top sliced bread toaster metal disc things from Coleman. Used it on my 123 and in order for it to toast your bread you have to turn up your stove full beans! I mean the metal plate has to start glowing red hot. The little Svea toasted our bread perfectly on that camping trip. But the whole stove was very hot but no issue what so ever. Now that I think about it what the heck was I thinking doing that on a gas stove, Kero is much safer.
The new ones say "Not for car/automobile gasoline/petrol." Not only do they make it clear, they write it to suit this website. :-) In the 1950s, unleaded gasoline was just gasoline with no additive at all. Now we use different words to mean "gasoline with no additives at all".
Well, bit of an update. Made a test rig out of a few fittings and results were as follows Svea 123r with replacement tank from fogas, set as lightly as possible. 40 reset and 45 psi open pressure Optimus 8r 85 reset and 90 psi open pressure Optimus 111 30 reset and 45 psi open pressure Tests were done repeatedly with little deviation and at 15 degrees C ambient All using replacement viton pips and only the 123r is adjustable, the others don't appear to be adjustable other than thinner pips or cutting springs down. The 8r srv is a concern now. Having problems with photos file type, will try another day
I have adjusted the 8r srv and secured it with thread locker, resets @ 60 psi and opens @ 70 psi. Not ideal but can't back it off much more due to thread limitations. Will be testing all new or refurbished srvs in future.
