Bought a 2003 Mazda B2300 with 38.5 k miles on it.
Low miles, but the owner never cleaned nor waxed it. He used it for landscaping work around the house and it showed on the beige leather steering wheel and vinyl interior.
So I turned to the detailing pro's on various detailing forums and can report on the following product:
3D Professional "All Purpose Cleaner" by 3D International LLC. Car Interior & Exterior Cleaner - Automotive All Purpose Cleaner
I'm in my 50's, and have used all kinds of interior cleaners from Turtle Wax stuff in the 1970's to Leatherique cleaners of late. But this product removed 10 years of grime from the leather steering wheel in minutes. At it was ground in dirt!
It took off the dirt in a 50/50 mix and I could probably have done 25/75 with water as it is that powerful. The steering wheel looks clean beyond what I had expected. (I thought it was a lost cause.) I'm going to re-dye it as the owner ground the finish right-off of the leather. I tried to find a new steering wheel but they're out of production according to Mazda.
I also sprayed it in the floor mounted cup holder and it broke down all of 10 years worth of "God only knows what" within 5 minutes.
Ditto for the vinyl seats and door panels.
I do not work for this company, and I do not know anybody at the firm.
3D Car Care - Car Wash, Car Wax, Auto Detailing supplies, Car Polishers, Car Buffers & accessories store
PS I also previously posted about their "HD Polish" as bringing back the shine to my 10 year old paint.
This company has a lot of strong support from the professional detailing community and I can see why. Time is money for them and 3D's products deliver.