Settling the balance on my vehicle in a couple of months and I will save the 510$ payment.

I plan to buy my next vehicle in cash. No more interest payments for this family.

I plan to save the payments I was previously making until we are ready to purchase our next vehicle. Will not be any earlier than 4 years from savings start date.

Where is the smartest place to save/invest those payments? Low to moderate risk. CD's, savings account, money market, etc?

Thanks!

Money market account. A CD is safe enough but generally does not work when you are adding money every month. If you find one that allows that then it would be ok as well

You could also do something like, save in a MMA for 6 months and then buy a CD. But another downside is that a CD plan depends on how well you know in advance the timing of buying the future car.

Also, nowadays you don't get a whole lot of extra interest from a CD.

I just saved mine in a money market account.

Both a money market account and a savings account would be liquid enough for your purposes. That said, Barclays' 1.0% money market account is the highest I've seen out there...

What I did was invest in a CD up front. Additional funds after that went to a money market account. When the CD matured, that went into the money market account. When I was ready to buy the car, I transferred funds from the MMA into Checking and wrote a check.