I have read several post about using ATF in the Primary! Is it worth switching over from Mobil 1 20W50?

 

Pros
Readily available anywhere.
Cheap, just make sure you get the proper type ATF.

Cons
None that I can think of

Did I mention it is cheap?

I don't use ATF, but there are thousands of people who do and swear by it, do a search here or at Harley Tech Talk's site, (if I'm allowed to recommend another HD site)

 

You could probably use cooking oil. It just lubes the chain. Any reasonable quality detergent oil will work just fine............

 

I have yet to hear of any cons.

 

I can't see where it would hurt anything, but I've never tried it. I use what gives me the best clutch engagement feel which, after trying several different (and expensive) specialty oils, turned out to be HD Formula+. I tried Redline MTL, Amsoil, Syn3, Rotella HDEO, and Mobil 1, but F+ works best for me. If I couldn't get F+ I'd go with Rotella 15W-40 HDEO, which works well, is easy to find, and is pretty cheap. A lot of people say Valvoline 10W-40 or 20W-50 works good too...

 

I'm with Lost1 as well. Tons of people use it, and I may give it a try some time since I can't seem to ever leave anything alone. But I really like the feel with Formula+ right now. I was a HD oil skeptic and it probably is over priced, but decided to give it a try and like it a lot.

Can't see any reason not to use ATF, and like I said might give it a try sometime when I don't have anything else to screw with. Are you not happy with the M1 in there? If not, give something else a try. That's how I came across F+. From all the reports here, everyone really likes the feel of the clutch on ATF and has no complaints. Like Dglide said, cheap too, another plus.

 

I've used Syn 3 first and recently put in Mobil 1 ATF. I liked the Syn 3 much better. Maybe I'll try F+ one of these days but I've already been buy a quart or two of Syn 3 here and there to do the oil, trans, and primary next.

 

In the 70's automatic trans fluid was standard issue in the primary for harleys.

 

ATF is good to go. No cons.

 

I think this hits the nail on the head, but I'm not even sure it needs an oil high in detergents. The primary doesn't need a high-tech oil, and IMO is better-off without it. The clutch disks need some friction to operate properly, and a synthetic with high-tech friction modifiers can cause the disks to slip, especially in marginal builds (engine output and clutch rating too close). Notice I didn't say "too slick," as I didn't want to sound like the wackos who perpetrated the "skating-bearing" myth some years back, but that's basically the bottom line.

I used a cheap fossil engine oil (10w40 or 20w50) in my old RK for 100k+ miles and had no problems, and use it now in my SG. I also think ATF may be ideal for the primary, as it is designed to work in auto-trannies that have clutches, bearings, and usually chains in their design. These trannies usually last for 100k's of miles and all use ATF, so why not the HD primary which isn't nearly so high-tech an environment? After all, it also has disks, bearings, and a chain. If I was changing over to ATF, which I've considered, I would go with Type F which has a different "shift modifier" formula compared to Dextron, which I suppose is nothing more than friction modifiers in reverse and makes the disks grab better. A tech friend who uses it says it works fine in his slightly modded 2000 EGC.

Another pro is that it is cheap, and I can't think of any cons for using it.