QuietStove.com

Sunday, March 20, 2011

Stove of the Week: Primus Omnifuel

If you want a stove that runs like a Swiss watch, then the Primus Omnifuel is your stove. It's precision engineering at it's best.  I mean this thing is a stovie's dream. Just look at that beautiful blue flame. 

The pump's action is a smooth as silk.  Everything fits together just so.  This is one high end stove.  But enough praise, let's take a look.  First, the burner.
It's a roarer style burner.  I expected it to be loud, as most roarers are, but I was pleasantly surprised.  It's really quite quiet for its type. However, one would hardly refer to the Omnifuel as quiet when the flame is on high.  The Omnifuel's three legs make it quite stable, and the pot supports are well engineered to accommodate a wide (and narrow!) assortment of pots.


The pump is sturdy aluminum, a far more robust pump than, say, a plastic MSR pump.  One interesting feature to the Omnifuel is it's rotating attachment to the fuel pump.  In order to run the stove, one rotates the fuel tank around the axis formed by the valve to the "ON" position (as seen in the below photograph).  The black grooved piece of plastic that you see immediately to the left of the pump rotates freely.
To turn the stove off, one again rotates the fuel tank around the axis formed by the valve into the "OFF" position.  In the "OFF" position, the dip tube, which would normally be in the lowest portion of the tank, submerged in fuel, now points upward and just draws air.  This air now flows out through the valve, clearing the fuel line and depressurizing the fuel tank.

It's worth noting that the threads on the Omnifuel's pump will fit Primus, Snow Peak, Sigg, MSR, Optimus, and Brunton fuel bottles.  Here, the Omnifuel is shown with an MSR fuel bottle.

The Omnifuel, as the name implies, will run on both of the standard petroleum liquid stove fuels, "white" gasoline (Coleman type fuel) and kerosene.  The Omnifuel is not designed to work on alcohol.  In a pinch, the Omnifuel can be run on unleaded automotive gasoline or diesel.  Of course it will not run as cleanly on unleaded or diesel and will require more frequent cleaning.  Use non-standard fuels like unleaded or diesel only when absolutely necessary.  The Omnifuel's manual states that leaded automotive gasoline should not be used "for health reasons."  As much as I like stoves and as much as I'd like to do a thorough review, I'm not about to personally test that health warning!  I imagine that you could run the Omnifuel on aviation gasoline or jet fuel as well, but again do so only when absolutely necessary.

Now, all the preceding regarding fuel is pretty standard fare for a multi-fuel expedition type stove like the Omnifuel, but there's another standard fuel out there that I haven't yet mentioned:  canister gas.   
The Omnifuel can run on the same gas canisters that power such popular stoves as the MSR Pocket Rocket and the Jetboil PCS.  It's really quite ingenious how Primus managed to allow not only liquid but gas fuel to be used.  The connection between the pump and the fuel line is a 7/16ths UNEF threaded male connector -- the exact same connector as on a gas stove.  If one wishes to use gas, one screws the connector into a canister of gas.  If one wishes to use liquid fuel, one screws the connector -- the very same connector -- into the pump.  Quite clever.  Indeed, other stove manufacturers, such as Brunton with the Vapor AF and Coleman with the Fyrestorm, are copying this idea.  I don't know for a fact that Primus originated the idea, but if Primus was not the first, they were among the first, and certainly the Omnifuel is a fine implementation of the idea..
For cold weather, the Omnifuel can operate with the canister inverted, that is it can operate in liquid feed gas mode.  Normally, one would invert the canister only if a stove has a pre-heat loop (aka generator) which the Omnifuel does not  However, since the Omnifuel can burn liquid fuel, which must be vaporized at the burner, it can therefore vaporize liquefied gas.  In liquid feed mode, the Omnifuel should easily operate in temperatures down to 0F/-18C, provided that you use canisters that contain some blend of either isobutane or regular butane with propane.  Canisters of 100% regular butane will not work in cold weather.  If one employs various means to keep the gas canister relatively warm and uses a winter grade fuel (a propane blend with no regular butane), one can operate the stove in far lower temperatures. The ability to run on canister gas, which requires no priming, is a big plus if the weather is really horrible and you want to cook inside your tent.  I personally do not find the idea of priming a stove inside a tent to be appealing.

The Omnifuel comes with jets with three different sized apertures, one jet for each of the three general classes of fuel:  gas (0.45mm), gasoline (0.37mm), and kerosene (0.28mm).  Each jet aperture size is optimized to burn efficiently the fuel for which it is intended.  The lighter the fuel, the larger the aperture size.  The heavier the fuel, the smaller the aperture.  While it is best to run the stove with the correct jet for a given fuel, my experience is that the stove will work reasonably well with mid-sized aperture jet on both gas and gasoline.  I have not, as of this writing, tried all possible combinations of jets and fuels.


Let's take another look at the burner.
Note the wire handle attached to the rigid portion of the fuel line.  This handle controls an "at the burner" valve.  A valve that close to the burner allows one to very precisely adjust the fuel and therefore the flame.  The Omnifuel has excellent simmering capabilities, no matter the fuel.

Now, a mild word of caution.  Stoves with a valve at the burner generally require a bit more maintenance than those that do not.  I am not saying that the Omnifuel is in any way unreliable.  It is a well designed, wonderful stove.  However, generally speaking, stoves with a simpler design, i.e. without the valve at the burner, require less maintenance.  With good quality fuels, there should be little problem.  However, were I going to some remote third-world location where the kerosene is likely to be quite unreliable as to its purity, I might be tempted to take a simpler stove, perhaps something like the MSR XGK.

At this juncture, let me make mention of a worthwhile aftermarket modification to the Omnifuel:  the Omnidawg silent cap.  The Omnidawg silent cap replaces the roarer plate in the Omnifuel's burner.  The Omnidawg greatly reduces the roaring noise of the burner.  I did a video review of the Omnidawg cap which I will link to below.  You will see me running the Omnidawg cap on an MSR Dragonfly stove because I didn't have an Omnifuel at the time I made the videos.  In actual field use, the Omnidawg cap works every bit as well on an Omnifuel as it does on the Dragonfly in the videos.  I haven't got the means to run the number of controlled trials necessary to establish this, but my gut feel is that the Omnidawg cap puts out more power than the roarer plate.  This perceived increase in power may be due to improved air gas mixing inside the cap, leading to increased efficiency in the flame.  Again, this is my gut feel only; I have no hard data on this.  Whether it increases efficiency or not, the cap runs extremely well and is very quiet.  People have asked in connection with the videos, so in hopes of heading off a lot of questions, let me publish the following information:  Omnidawg caps are available on eBay through seller "hugecanine."  The caps are hand made and are not always available.





Note:  I was approached by the producer of the Omnidawg cap and asked to do a review.  As a part of the review process I received an Omnidawg cap.  Other than the cap itself, I received no remuneration for my review.  The receipt of the Omnidawg cap was not contingent on the nature of my review (in other words I didn't have to promise to do a positive review in return for the cap).  Further, I receive no part of the proceeds from the sales of Omnidawg caps.  All comments regarding the Omnidawg cap on this page and in the linked videos are strictly my own and do not necessarily reflect the views of the producer of the Omnidawg cap.

Well, there you have it, a brief look at the Primus Omnifuel, a truly wonderful stove and a personal favorite.

HJ

The Primus Omnifuel
What's good about it?
Truly multifuel, burns all standard petroleum based fuels, including canister gas.
Precise, easy simmering
Precision engineering.
Relatively quiet for a roarer type burner
Extremely quiet with an Omnidawg cap
Powerful
Reliable
Stable
Efficient

What's bad about it?
Expensive
Relatively heavy compared to typical canister gas stoves
A bit bulky compared to typical canister gas stoves
May require more maintenance than simpler designs

Overall, highly recommended.

Other Primus Omnifuel Related Posts
Primus Omnifuel vs. MSR Whisperlite Universal -- A comparison

28 comments:

  1. Hikin' Jim: these are excellent reviews! Thanks for the very practical descriptions and opinions.

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  2. You're very welcome. I'm glad you're finding them helpful. HJ

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  3. Great review. I have been reading about people using this particular stove on home made biodiesel manufactured with unused vegetable oil as well. I have yet to see a video of someone using an Omnifuel on biodiesel, and in particular would like to see someone post a video of the use and priming of one, but I think there is sufficient anecdotal evidence to suggest it is possible. I have also read about the MSR XGK and the Dragonfly using biodiesel too, so it's not exclusive to the Primus. Beyond these three, I know of no other stoves with the full range of fuel options.

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  4. Hi, Anthony,

    Interesting. I've not tried using biodiesel yet. I've read about people trying it. Apparently some stoves can burn it, and some can't. If I were to bet on a particular stove, it would be the MSR XGK which will burn darned near anything.

    HJ

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  5. Does anyone know where I can get the little metal piece that fits over the flame that disperses the flame, making it burn properly? Mine was loose, it fell off and I lost it.

    thanks,

    Dan

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  6. Dan,

    The part you're looking for is typically called a spreader plate or flame plate. A plate for the Omnifuel is included in the Omnifuel service kit which is available at Campsaver.com -- http://www.campsaver.com/omni-fuel-maintenece-kit-p731770

    Best of luck.

    HJ

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  7. Hi there,
    after testing the new MSR Whisperlite Universal and the Omnifuel - which one would you choose?
    BTW- thanks for the great blog - keep up the good work!

    As a side note - you can now get a mf burner(made by Optimus) for the Trangia as well.
    The gas burner for Trangia(made by Primus)is WELL worth the investment!!
    Regards from Sweden,
    Jonas

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  8. Hi, Jonas,

    I generally prefer the Omnifuel to the Whisperlite Universal. I think the Omnifuel is the better built stove, BUT the Omnifuel, at least in the US, is more expensive (or will be when the Universal becomes available). HOWEVER, if I were dealing with fuel supplies that might be of poor quality, as in a poor country, then I would pick the Universal. The Universal will be less like to clog on poor quality fuel.

    The latest Trangia multifuel burner, the X2, is from Primus. Trangia stopped using the Nova burner a couple of years ago, about the time that Optimus was sold to Katadyn.

    HJ

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  9. Hi Jim,

    yes you are correct in that the mf burner, X2 is made by Primus - I got it wrong - as Optimus did when Katadyn bought them......
    I have a omnifuel stove that I´m quite happy with for liquid fuels BUT I don´t particalarly like it when using canister gas(for conveniance when cooking with my son) So i wonder if the MSR Universal is more fuel efficent when it comes to canister gas in comparison with the the omnifuel.
    BTW - have you ever tried a Kap Arctic stove?

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  10. Hello again, Jonas,

    I don't know which is more efficient on gas, the Omnifuel or the Universal. I was allowed to have the Universal for about 3 weeks for testing, but I had to return the stove thereafter. I did as much testing as possible to understand the stove, but unfortunately, I did not have time to do detailed technical testing of the type that would allow me to accurately measure fuel consumption per liter of water boiled.

    I would **love** to try a KAP Arctic stove. They fascinate me. So advanced for their day, and still a very good stove by modern standards. Unfortunately, they are quite rare and quite expensive to acquire. The closest I can get is mounting a 111C or 111T burner in a Trangia or perhaps something like a Nova burner. But I would love to see a genuine KAP Arctic stove some day.

    HJ

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  11. Hi Jim,

    I have been looking high and low for a .32mm jet from the new Trangia x2 for use with the Omnifuel, and cannot find one... Decided to try and find one for use with my Omni as I am lazy and would like to be able to use both Kero and white gas whithout changing the jet as I have read about on the C.C.S. site. Do you know where to get a .32mm jet? Your help would be appreciated.

    Best regards,
    Mike.

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  12. Mike,

    Two things:
    1. If you really want a 0.32mm jet, then you'd probably need to either contact Primus or Trangia.
    2. However, I've run my Omnifuel on gas with the jet meant for white gasoline, and it runs just fine. I don't really think you need a specialized jet. Give your white gasoline jet a try with canister gas and let me know how it goes.

    HJ

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  13. Hello Jim,

    Contacted Trangia and they have a repair kit that is roughly $50 with shipping, and it only has one .32mm nipple (the rest is burner plate, .28mm nipple, preheat pad...stuff I don't have use for).

    What about kero and white gas? Do you think kero will run ok through the .37mm nipple? Longer preheat? Less heat ouput? When tinkering with stoves sometimes it goes beyond the point of no return and there is a catastrophe...that I would rather avoid which is why I ask.

    Can't try canister gas as I do not use canister fuels. Liquids only.

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  14. Mike,

    The general rule with jet aperture sizes is to "go down." In other words, if you want to burn canister gas and white gasoline, go down to the smaller jet, the white gasoline jet. So, in this case, if you want to burn kero and white gasoline, choose the kero jet which is the smaller of the two.

    You'll get best results by switching to the optimum jet for each fuel, but if you only want to carry one jet, then choose the smallest jet that goes with the fuel you want to use.

    HJ

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  15. Thanks HJ.

    I will try the .28mm with white gas and then try the .37mm with kero and see what happens.

    I am notorious for losing small items while out and about and want to find one jet to rule them all (if possible).

    Mike.

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  16. I think the 0.28mm jet will work far better with white gas than the 0.37mm jet will work with kero. The 0.28mm jet will not have as much power with white gas as a 0.37mm jet might, but it should burn cleanly. The 0.37mm jet with kero will probably burn a little yellow.

    HJ

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  17. The review states that the accessory cap is hotter than some others. What is responsible for that? Since the valving is unmodified I presume that the same amount of fuel is being delivered (and burnt) in all cases. Better fuel / air mixing maybe?

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  18. Bruce,

    Yes, exactly. The air/fuel mix is improved when using a "silent" cap as opposed to using a simple flame spreader. The test results I've seen indicate much better combustion and very low carbon monoxide emissions. In short, a silent cap is far more efficient.

    HJ

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  19. Hi Jim. Great review.

    I've just received my new Primus Omnifuel bought on Ebay and I need a small consultancy.

    The dip tube on the punp rotate inside his housing (in the black plastic pump head). It seams normal but I'm not sure it is a defect.

    What is your opinion ?

    Thaks in advance, Stefano - Italy



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    Replies
    1. Hi, Stefano,

      Sorry not to reply sooner. I just returned from being away on vacation for our Labor Day holiday here in the United States. If the fuel dip tube is picking up fuel normally, it doesn't matter if it rotates a little bit. The only thing that would matter would be if the fuel dip tube is so loose that it might fall out.

      What do you think? Will the tube fall out? If it will fall out, it must be repaired.

      HJ

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  20. Would the omnifuel be able to burn JP8? And If so with what jet?

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    1. Yes, an Omnifuel should be able to burn JP8 without any problems. You should use the kerosene (0.28mm) jet.

      HJ

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  21. Thank you kindly for your answer. Excellent job on the reviews! Keep up the good work! :)

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  22. Have you done a review for the Coleman Exponent multi-fuel stove? What do you think of the Coleman especially in comparison with the Omnifuel?

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    1. Hi, Buddy,

      Coleman has decided to stop making backpacking stoves. At this time, I don't have any plans to review any Coleman gear.

      HJ

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  23. Jim, thanks for the great review. I've been running the Omnifuel for almost a year now and it's become my favorite stove. I agree that it burns canister (iso-butane) gas on the white gas jet just fine and I never bother to switch. One issue that can crop up, and it's one that caused me to return my first Omnifuel to Brunton, is the tightness of the jet in the burner head. I've had the problem of a fully pressurized and heated stove emitting a small yellow flame while running. The flame never extended beyond the spreader plate and had a distinct orientation that always pointed back towards the vaporizer tube/valve assembly (think a small flag waving in a breeze). I finally figured out that the jet was not screwed tight enough into the vaporizer tube. While the jet was tight it was not tight enough to prevent what I assume was an air leak along the jet threads. I had to really crank the jet down using the stove tool and make sure it was on there extra tight. Problem solved. Since this is the second Omnifuel I've seen this issue on I have to think it could be a common problem. Beyond that this is a great stove!

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  24. Brian,

    What you're saying makes sense. I've experienced that with other stoves.

    HJ

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