The Magnum / ASP .15 XLS engine Weighs 6.8oz w/muffler and 5.9 oz W/O muffler.
That might make them pretty huge in relation to the other engines unless you are looking at a MVVS .15 or Rossi .15 or something.
The Chinese put on a huge carburator with a large intake bore, so you have to let the engine rev up higher than the other engines do, otherwise it would have poor fuel draw with larger props on it. But they do run pretty good, if you let them rev up good and don't try to load them down with too big of a prop.

Fox's website says the .15's weigh 6.0 ounces, so I am not sure if they have changed anything or not.
My Fox .15's run just fine off of 5% nitromethane glow fuel, with 18% oil with 5% or 50% castor oil in the blend. You want at least a little castor oil in the fuel. I have been running Omega brand label fuel lately.

I think the older Fox .15 Schnuerle bushing engine is more lightweight than the ball bearing version. But I haven't tried weighing one recently though.


I was pleasantly surprised as to how well this old Fox .15 Schuerle bushing engine ran and idled without a muffler on it. The Tach I was using had problems with the shade though. i have a better Fromeco Tach now.

[youtube]http://www.youtube.com/watch?v=CVehnv0uBfg[/youtube]


Here is a Fox .15 BB RC engine on my little Sportster type of plane. it is way overpowered with the engine too. I can do nice slow rolls and four points at about 1/2 throttle.
I had to run the engine extra rich for a number of flights at first, since it was new. Gradually I leaned it out more and more over time. But it still needs some time on it though.



Here is my H.O.R. combat plane with a fox .15 on it too. This one is a old old engine but well broken in now. Still runs really good and pulls strong. I actually have to richen it up a little more to keep it under the max RPM rule for the combat class.



Now I did get a couple of Magnum .15 engines back when Hobby People had them on sale cheap. I was pretty satisified as to how well the one I ran did.
I haven't put it on anything yet. Myfox engines have been working just fine instead. so these are a just in case of a really bad day flying combat and I kill a few engines in the process.
here is a short video of me messing around with one last year.
[youtube]http://www.youtube.com/watch?v=4ExQM-DkRN4[/youtube]