Johnny, reason car loans from manufacturers are so low are that some of the lending is priced in to the purchase price, new car sales are at record lows so they need to urgently sell current and old stock so they take a hit and also whilst they advertise 1.9% (for example), sometimes/ often but not always it's not a genuine rate. There can be inflated e-fees, admin costs, lending costs etc added into the monthly repayment. Or set balloon / residual % and terms and upfront required that may not suit you but suit the vendor. We've done plenty of loans at higher 'interest rates', but the repayment is lower with the same finance amount/ term etc. So we are effectively cheaper, even though the rate is higher. I'd always suggest that if you are comparing any finance, add up all your repayments/ balloon payments/ upfront payments etc and go with the lower cost one, all other things being equal.
