Flat rate versus effective rate, why 2.48% is not really 2.48%

Every car loan quote in Singapore leads with a number that looks reassuringly small. Two point four eight percent. Next to a mortgage at three or four, it sounds like a bargain.

It is not comparable, and the reason is worth understanding before you sign anything.

Two ways of charging interest

A reducing balance rate charges interest on what you still owe. Pay down the loan and the interest shrinks with it. This is how home loans, personal loans and credit cards work.

A flat rate charges interest on the original amount for the entire term, no matter how much you have repaid. Car loans in Singapore work this way, and always have.

That difference is the whole story.

What it looks like on a real loan

Borrow $42,000 over five years at 2.48% flat.

The interest is worked out on the full $42,000 every year, for all five years. That is $1,041.60 a year, or $5,208 total. Add it to the loan, divide by 60 months, and you get $786.80 a month.

Now look at what actually happens. By year four you have repaid most of the loan. You might owe $10,000. But you are still being charged interest as though you owed $42,000.

The effective rate

Work out what reducing balance rate would produce the same monthly payment, and you get the effective rate, sometimes called the APR. That is the number that compares fairly against a mortgage.

Roughly speaking, the effective rate on a Singapore car loan is a little under double the flat rate quoted.

This is not a trick and nobody is hiding it. Flat rate quoting is the industry standard here, every dealer and every bank does it, and the actual dollar cost is disclosed. But if you have been mentally filing a car loan next to your mortgage, you have been comparing two different things.

What actually matters

The effective rate is useful for comparison. For deciding, the number to look at is simpler.

Total interest in dollars. On the loan above, $5,208. That is what the borrowing costs you. Ask for it on every quote and compare that figure across options.

Total cash out of pocket. Downpayment plus every instalment plus fees at signing.

Both are concrete, neither requires you to trust anyone's rate quoting, and both are easy to compare across two deals.

Where the flat rate structure bites hardest

Longer tenures cost disproportionately more. Stretch the same $42,000 from five years to seven and total interest rises from $5,208 to $7,291. You pay $2,083 more for the same car, and the monthly drops by $200. Whether that is worth it depends on whether you need the cash flow, but it should be a decision rather than a default.

Early settlement does not save what you expect. With a reducing balance loan, paying off early cuts remaining interest sharply. With a flat rate loan, the interest was calculated upfront on the full amount. Lenders apply a rebate formula, usually the Rule of 78, which returns some of the unearned interest but not all of it, and there is typically a settlement penalty on top. Paying off a car loan early is rarely the win people assume.

Borrowing more compounds twice. A larger loan at a higher rate over a longer term is three multipliers moving the same direction.

What to ask

1. What is the total interest in dollars over the full tenure.
2. What is the effective rate, not the flat rate.
3. What is the settlement figure if I clear this in three years.
4. What fees are payable at signing, itemised.

Any lender or dealer should answer all four. The answers matter, but so does whether they answer without hesitating.

We covered the related trap, where the monthly is engineered to hit a target while the total cost quietly grows, in the cheapest monthly is rarely the cheapest car.