The old iron/steel P&L technology generally needs all the help it can get. The Castor isn't there just for lubrication; the unburned oil carries a tremendous amount of heat out of the engine, also. When you got the L&J Fox, Larry's directions were pretty adamant about having 29% total oil, and 25% of that as Castor. He stands behind his products, but only if directions are followed (remember, he also advocates a minimum of 10% nitro, and has no problems with going to 15% if the situation warrants). Pretty much the same holds true for the T&L Max .35 - - 25% castor minimum. Email Tom if you'd like to see if his directions have changed, but he wants me to run 23% all-Castor fuel in my (his) ringed ST V.60, too!

While you probably won't ruin either engine immediately by using a lower oil content, there are other potential problems, too. A high percentage of synthetic oil can dissolve the varnish on the piston. While this sounds like a good thing, it can leave you with no compression on a well worn engine (the varnish can add considerably to the piston seal). Heck, we used to run Missile Mist in our old Fox .35s, and then wonder why the great performance didn't last . . .

Ty,
Both engines are brand new. The first 2 bench runs on the T&L 35-S were with the 10/29. Third run was with the 10/22. All runs a fairly rich (but not slobbering) 4-cycle. Haven't run the L&J Fox yet, after the first tank of 10/22 I got nervous and decided to get some opinions before further running. I'm leaning towards sticking with the 10/29, but how to prevent it from loading up and extingishing the spark? Should I be running a hotter plug (currently OS A3)? Also is there some additive I can put in the fuel to prevent carbon build up?

thanks,
Ken

Interesting you should ask about oil content.  This is a subject I have been mulling over for some time.  There is lots of info on the internet and a lot of that is "that's what we have also done so that is what we will do" type of thing.

If you are comfortable with the engine builders recommendations then you should go that way; they know their engines.  That is the conservative approach and there isn't anyting wrong with that.

However, I have gotten to the point where I like to challenge common convention and push the limits in one direction or another.  If you have any interest in model diesels and haven't seen this thread on RcUniverse, you might find it interesting in experiences using very low % ether or NO ether model diesel fuel with minor diversions into the question of lubrication.

http://www.rcuniverse.com/forum/m_4561055/mpage_1/key_/tm.htm

In my search for knowledge I have been running several engines on various mixes (emperical testing) and a lot of reading on whateve I can find on these subjects. 

Recently I ran across an old (2001) control line newsletter called Linecheck. This was a shortlived newsletter published in the UK and more or less concentrated on control line racing. Issue #10 Jan 2001 has a particularily interesting bit by Andy sweetland who writes on metal tanks and oil in fuel.  Now the requirements of a team race engine and one we use for stunt or sport flying are quite different. However, engines are engines.

Here is a link to that newsletter:

http://www.noclassmac.com/Downloads/download_index.html issue #10 January 2001 Andy sweetland writes on metal tanks and oil in fuel.

Have a read, good a read.  A little hint, one fellows University thesis was based on model size engines. To summarize his results, he found that higher %'s of oil caused the engines to run hotter than lower %'s. His test where done in the mid 70's using an engine with a steel cylinder / cast iron piston (BUGL team race engine).

There you go, something to think about.

cheers, Graham in Embrun near Ottawa Canada

Bill, agree to the "T" about the Lay ST .51's  mine runs extremely well when I pour the Castor to it!

Jim Pollock

Hi Ken,

I add about an ounce to an ounce and a half (almost 1%) of Klottz to my gallon of 10/29 when I run "new" old engines.  Just enough of the synthetic to help keep the engine a little cleaner inside, but still all the castor they need to run correctly.  If it's a Fox 35 and has always been run on all castor, I only run a tank or so throught them of the synthetic "blend".  Too much and it just might clean up the nsides so much that the compression is gone.

Bill <><