Ok, I can't stop thinking about this... in my mind I still think it's better to split the payments.... so back to the loan calculators I went....
Ok... lets see if I can do this without screwing it up....
2 loans exactly the same:
Loan Amount: 15,000
Interest Rate: 6%
Term: 10 years/120 payments
If you were to pay a lump sum of $1000 extra principal ever 6 months, you would get the following:
Loan #1
Pay off time: 54 months
Interest over 54 months = $2159.79
Loan #2
Interest over first 54 months = $3334.53
Interest over next 31 months = $815.75 (with $1000 extra applied)
Total Interest = $4150.28
Total Time to payoff both loans = 85 months
Total Interest on Both loans = $6310.07
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Now if you split the payments ($500 each every 6 months)
Total Pay Off time: 72 months
Total Interest for both loans: $5939.78
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Again, this is very generic and a different situation could result in totally different results..... if you want, you could send me the details and I could do the math using your figures.