Deducted RV as second home sold it in Sept. and bought newer one.

No, a personal loss is not allowed to offset other income.  If you paid more for your RV than you received from the sale, and you never used the RV in business, depreciating the cost of it, then there is nothing to report for a personal loss.

Yes, you can claim interest on an RV as a second home. Interest on the first one up to the sales date, then on the second one from the purchase to the end of the year if you itemize deductions, can be used as your second home mortgage interest.  The most common deductions are medical expense that is above 7.5% of your income, mortgage interest, property taxes and donations. The standard deductions are printed for you below. 

• Standard Deduction vs. Itemized Deductions: Which Is Better?

For single taxpayers and married individuals filing separately, the Standard Deduction is $13,850 in 2023. 

For married couples filing jointly is $27,700, and  

For heads of households, the Standard Deduction is $20,800

If you're at least 65 years old or blind, you can claim an additional deduction in 2023 of:

• $1,850 for single or Head of Household
• $1,500 for married or Qualified Surviving Spouse.

If you're both 65 and blind, the additional deduction amount is doubled.