this is for one gallon:

to water,mix 1/4-1/2 cup rubbing alcohol...add 2-3 good drops of dishwashing liquid.

Another bit of info.  For cleaning glass and other surfaces don't use any cleaners with ammonia in them. This degrades the vinyl adhesive.

Also a wet app fluid I use, Similar to bannerone's  For a quart I put 1/4 rubbing alcohol and 3/4 water and add 2 drops dish washing detergent.

Could I clean with an amonia based one first and then with a non-amonia based one after to minimize the damage to the adhesive ? The amonia based cleaners just do a way better job with the removal of wax, oils and road grime .

there is nothing better for removing wax and oils than a mixture of dawn dishwashing detergent and water. They are using it now to clean oil off of the birds down in the gulf.

Ok, I'll have to try dawn on road tar and see how it works . BTW I have noticed that the heavy duty ammonia based glass cleaner work AWESOME for removing glue left over from old decals and stickers !! I just pulled some stickers of my Jeep that have been on there for about 6 years and they came off without the glue . The amonia made quick work of it ..next to no elbow grease .

I tend to use 90% Iso. Alky for cleaning prep and for cleaning off old residue.  You'd be surprised the difference between the 90% and 70% will make. 

I'll have to give this homemade app fluid a try, I usually go dry, but sometimes wet is necessary.

Thanks!

The cheapest store brand you can find - even dollar store

I think the same stuff that cuts greese