My Regal has white interior, I use "Mean Green" that I buy at the local Dollar Store, it works great with no ill effects. Cant beat it for the money.
When I had a white interior on an old 442 the big thing in getting it clean was using a scrub brush. Otherwise you just push dirt around. Use lots of paper towels and do not let it dry. Wipe it often.
Wow! Thanks for all the suggestions. If nothing else, I will have the cleanest dirty seats in existense! lol! They are more just dirty from years of use and not really a spot stain. And the drivers door panel on top where your arm lays all the time is the worst. I think it may be too far gone and the stains may be set but I will give a few of the ideas a shot and see what happens.
Do you mean SMS, can't find SEMS doing a search. Is that same companay that has all the matching old time fabrics? Would like to get some dye for a couple of touch up spots.
When I had a Suncoupe with white interior we used Formula 409 if thats still made it worked great with a soft scrub brush
I've had great luck with Meguiar's Marine vinyl cleaner and protectant. Nothing like going to the boat store for your Electra.
Ditto on the Murphy's oil soap for the interior. My car's previous owner stored the car last year in an unheated barn. You can imagine what it looked like in the spring. Murphy's got the interior looking brand new. I'm not sure either if it will work on heavily stained sections though. As for the Mean Green, try it on the heavy stains if Murphy's doesn't work. It's awesome on tires/whitewalls though! A little scrub has them black as night and white as snow. And the dust doesn't stick to them like it will with "tire shine" products!!
Look here: http://sem.ws/?home=1 OOPS. Looks like a few already answered this. Anyway, yes SEM products work well.