Bicycle Mechanics - What lube to use for binding STI shifter

I've had very good luck bringing back dead or dying STI shifters and trigger shifters having been successful 6 out of 8 times. But I 'm having trouble bringing back a formerly dead STI to a nice smooth operating unit and I would like to know what lubricants other BF members have used for this job. Here are the details.
A fellow BF member picked up this shifter set from a used bike. He soaked it in solvent, (mineral spirits I think) and was successful in getting the unit to engage. I obtained the shifter set, and noticed the right shifter would bind when it engaged in a downshift requiring my full hand on the handle to shift. Upshifting with the paddle is no problem, nice and smooth. I sprayed the inside of the shifter repeatedly with Finish Line Teflon Plus, the lubricant I've successfully used to repair other shifters in the past. The Teflon Plus worked to some degree as the binding is now reduced, but not completely gone. I only need two fingers to shift, but it's still not smooth like my other STI shifters.
My question is, has anyone used another lubricant such as spray oil with any success to lubricate one of these units? I'd like to bring this shifter all the way back to completely smooth operation. Thanks for your time.

Would this be an Ultegra 9 speed?

Would this be an Ultegra 9 speed?
No, sorry, I meant to put that in the original post. It's a 105 8speed.

What do you mean by upshift and downshift? Technically an upshift with the rear derailleur is done with the smaller shifter behind the brakelever, shifting up to a higher gear. With the front shifter an upshift is done with the brakelever.
I've always used WD40 to clean and loosen STI shifters, with good results.

Al

What do you mean by upshift and downshift? Technically an upshift with the rear derailleur is done with the smaller shifter behind the brakelever, shifting up to a higher gear. With the front shifter an upshift is done with the brakelever.
I've always used WD40 to clean and loosen STI shifters, with good results.

Al

As it state in the original post, the right shifter is the problem unit. I call an upshift when I shift to a smaller rear gear for speed using the shifter paddle (as the post states, upshifting with the paddle is no problem). I call downshifting when I shift to a larger rear gear for hills or slower speeds and, as you've stated, that requires using the brake lever.
Yes, WD-40 is a great cleaner, but I think the previous owner cleaned it thoroughly when he soaked it in solvent. I'm looking for a lubricant recommendations.
However, you might have a point here, maybe additional cleaning is in order. I'll have to think about that one. Thanks.

Yes, WD-40 is a great cleaner, but I think the previous owner cleaned it thoroughly when he soaked it in solvent. I'm looking for a lubricant recommendations.
However, you might have a point here, maybe additional cleaning is in order. I'll have to think about that one. Thanks.

Your first posting was accurate but I wanted to make sure that I understood it. As you know some folks have a different definition of upshift and downshift for bikes.

How about the cables and housings? Excess friction could account for the problem you are having, especially in the short housing at the back, just before the rear derailleur. You could test this by lubricating the cable, if the lubrication improves shifting you probably need new cables and housings.

As for a shifter lubricant, I think your Finish Line should be just fine. I would probably use what I put on my chain, home brew or Purple Extreme.

Let us know how it turns out.

Al