Todays leathers are coated. Trying to use a "conditioner" is not going to help unless you have gone through it. Some just make the leather feel slimy. Some can be absorbed to extent.
I have an Ecru interior and what works is good old Woolite mixed 6:1 (6 parts Distilled Water, 1 part Woolite) in a spray bottle. Spray the leather, use a horsehair brush to loosen dirt. Wipe off excess, use a damp clean towel and wipe off the rest.
Once dry, I add Zaino Z-10 leather care as it's the closest thing to new leather smell I've found.
Leatherique works well on older leather, but the "oil" first used to clean leather works well too. It's just cheaper to use Woolite, which works better and less mess.
I did one car (2001 MB) that the customer ALWAYS used Leatherique. He was complaining that the seats had one spot that felt odd. So, I had one of my vendors remove the leather covers and we found that the Leatherique oils have worked it's way to the foam and started it to deteriorate. We guess from the heat added the effect. Never thought I'd find that. The oils got through via the seams as he was anal about treating seems fearing they would weaken and break.
Now this was a first I've ever heard or came accross this. I just told the customer he can still use it, just keep it away from seams.
Go and try the Woolite. You will be suprised how well it works.
Regards,
Deanski