The standard method for jump starting a car is sound for one situation only: a flat battery, a 12-volt system, a second car with a healthy battery, and an owner’s manual that says nothing different. Outside that situation the method stops applying in at least five identifiable ways, and on one step, whether the engine of the donor car should be running, two Australian motoring clubs publish opposite instructions. The finding is therefore short. The handbook for the car in the driveway governs, a roadside service is the fallback when the handbook is unclear, and the generic sequence found on most websites is a floor, not a ceiling.

That finding rests on three documents: a guide from RACV published in March 2026, a jump-start FAQ from RAC in Western Australia, and the jump-starting section of a 2023 Kia owner’s manual for a hybrid model. This article is general information about how to jump start a car, not advice for a particular vehicle. The owner’s manual and a roadside assistance provider are the authorities for any given car, and nothing below replaces them.

Two limits apply. Three documents are a narrow base, and the manual covers one manufacturer’s hybrid, so every row in the table later in this article names its source instead of claiming a rule for all cars. The article also prints only the figures those documents print. It does not rate batteries, price replacements or compare equipment, because none of the three does.

The standard method, and who agrees on it

RACV’s guide, published in March 2026, sets out the sequence most drivers have seen in some form. Written as steps, it reads as follows.

1. Switch both cars off, park them or leave them in neutral, and put the handbrakes on.
2. Attach one red clamp to the positive terminal of the flat battery.
3. Attach the other red clamp to the positive terminal of the charged battery.
4. Attach one black clamp to the negative terminal of the charged battery.
5. Attach the other black clamp to “a piece of bare, unpainted metal on the car with the flat battery (such as a nut on the engine block)”. RACV adds that this clamp must not go on the flat battery’s terminal.
6. Start the charged car and let it run for one minute.
7. Start the car with the flat battery, and leave both cars running for several minutes.
8. Disconnect the clamps in the reverse order.
9. Drive for 10 to 20 minutes.

Most of that sequence is uncontroversial, and the step people argue about most is the fifth: the habit of clamping the last lead to the flat battery’s negative terminal because the colours match. RACV says not to, and the Kia manual agrees, which matters because a motoring club and a vehicle manufacturer have no obvious reason to coordinate their wording.

The manual gives its reason in two parts. A battery produces hydrogen gas, and the manual says that gas “will explode if exposed to flame or sparks”. It then instructs the reader not to connect the booster’s negative directly to the discharged battery’s negative, but to a metallic point “far away from the battery”. Neither document says which individual connection is the likeliest to spark, and this article does not guess. What the two sources establish is the instruction, the hazard it addresses and the agreement between them.

Both documents also steer the reader away from improvising. RACV states a rule: “Always refer to your car’s manual for model-specific instructions”. The Kia manual recommends that, if in doubt, a competent technician or towing service should do the jump start. RACV also notes that an incorrect jump start can cause problems with a car’s electrical systems, which is the stated cost of getting the order wrong.

The sequence quietly assumes four things: that the system is 12 volt, that the flat battery is in a usable physical state, that the donor car can safely act as a donor, and that the battery is flat for an ordinary reason, such as a light left on, and not because it is failing. Each is a place where at least one of the three sources says the method no longer applies, and the sections below take them in turn.

Where two motoring clubs disagree

The sixth step is where RACV and RAC part company. RACV tells the reader to start the donor car and let it run for one minute, then to start the flat car and leave both running for several minutes. RAC says the opposite. Its FAQ states that once the leads are correctly connected the reader should not start the car with the good battery, and that “the engine of the vehicle with the good battery should not be running during the procedure”.

RAC gives a reason. Leaving the donor engine off “helps reduce the voltage differential between the two batteries, which reduces the risk of a spike”. The page recommends spike-protected jumper leads, and it concedes that “there is always a risk of electronic damage when performing a jump start”. The two clubs also differ on what follows the jump. RACV says to drive for 10 to 20 minutes. RAC says that after a battery has been depleted it “will need a full recharge using a battery charger”.

The table leaves out any judgement about which club is right, and that is deliberate. Neither club publishes test data in the pages read, the Kia manual does not state the donor-engine step at all, and a ruling built on thin evidence would only add a third opinion to a field that already has two. What can be said is narrower. Where the owner’s manual covers the point, the manual decides it, and RACV says so in terms. Where the manual is silent, the reader holds two published positions from two motoring clubs, and the safer course is to hand the question to a roadside service instead of choosing between them in a cold car park.

Five cases where the standard steps stop working

The table sets out the five situations the sources identify. Each row names its document, and none adds a rule that the document does not state.

The table leaves out three things. It says nothing about the health of any battery, because none of the sources offers a test. It carries no costs, because none prints a price. And it is not a model-by-model list: the hybrid rule comes from one manufacturer’s manual for one hybrid, and this article does not extend it to other makes, which may word the point differently or not address it at all.

Two rows answer questions that readers ask often. The first is whether a hybrid can be used to jump someone else’s car. The Kia manual says no, and gives the reason: the hybrid’s own 12-volt battery can be damaged. It is easy to assume that a hybrid has power to spare and should make a good donor, but the manual’s wording points the other way. Whether another manufacturer’s manual says the same is a question for that manual.

The second is the 24-volt row, where the manual’s language is strongest. Damage “beyond repair” is its phrase, and it attaches to the starting motor, the ignition and other parts. The instruction to use only a 12-volt system is about the source of the power, whatever sits on the other end of the leads.

Leads or a pack?

A portable jump pack avoids the need for a second car, which is its obvious appeal, and RAC recommends spike-protected leads for anyone who does use a donor. Neither the RACV nor the RAC page compares leads with a pack, and this article names no product and prints no rating, because nothing in the sources supports one. The handbook governs either way, and a pack does not remove the 12-volt requirement or the warning about a frozen battery.

When another jump is the wrong answer

The battery that goes flat again soon is the case in which the method works and the problem remains. RACV’s wording is direct: if the battery dies again soon, “it may be time for a new battery”, and the reader should not rely on continually jump starting. The qualifier “may” is RACV’s, and it is right to keep it. Take a hypothetical driver whose battery goes flat once, after an interior light was left on overnight. That is one event with an obvious cause. If the same battery goes flat again soon afterwards, it is a different event, and the first jump start has done nothing to explain it. The method restarted the car; it did not diagnose anything.

RAC’s point about recharging touches the same case. RAC says a depleted battery needs a full recharge using a battery charger, while RACV says to drive for 10 to 20 minutes. The two clubs do not agree on whether the drive is enough, and this article does not decide it. Both statements treat the jump start as the first part of the job and not the whole of it.

This section gives no guidance on choosing a replacement, no cost and no method for testing a battery, because the sources give none. The Kia manual’s recommendation applies here as it does elsewhere: where there is doubt, a competent technician or towing service is the safer way to get the car moving.

What forums get right and wrong

A common view among drivers online is that connecting red to red and black to black has always worked, and for a healthy, plain 12-volt battery that is true often enough to persuade people. The weakness of the view is that it says nothing about a hybrid donor, a 24-volt supply, a frozen battery or the voltage spike RAC describes, because in the ordinary case none of those arises. A method that has always worked has only ever been tried in the ordinary case.

The same discussions contain a more useful habit: preferring bare metal to the flat battery’s negative terminal. That habit has a stated reason in the Kia manual, hydrogen gas and sparks, and it has the support of RACV. It is the part of the folklore worth keeping.

Check the Handbook First

This article asks for one step, and it takes a few minutes. Find the page in the car’s owner’s manual headed “jump starting”, or its nearest equivalent, and read it before the day it is needed. Note whether it addresses the donor engine, whether it says anything about hybrids or the 12-volt requirement, and whether it names a particular terminal or metal point for the last clamp. If the page is silent on any of those, the roadside service number is the next thing to store in the phone.

Sources: RACV, Car battery guide: how they work, when to replace them, and how to jump-start, 26 March 2026 (https://www.racv.com.au/royalauto/transport/cars/car-battery-guide-how-to-know-if-it-needs-replacing.html); RAC, Car Doctor: jump start (https://rac.com.au/faq/cm_car_doctor_jumpstart); Kia owner’s manual, hybrid (model code MQ4), 2023 edition, Jump-starting (https://ownersmanual.kia.com/full_webhelp/MQ4KH/2023/en_US/topics/t00636.html)

The GST registration threshold of $75,000 is tested on turnover, not profit, over a rolling 12 months, and it is tested forward as well as back. A business can stay under $75,000 in every financial year and still be required to register. The common shorthand, “under $75,000 a year”, describes neither the measure nor the period.

This article sets out how the Australian Taxation Office (ATO) describes the test, works one hypothetical through month by month, and names what the figures leave out. It is general information only. It does not say whether any particular business must register, and the ATO is the authority on that question. The wording below follows the ATO’s Registering for GST guidance as last updated on 23 May 2025, together with the business.gov.au page on the same subject.

What counts as GST turnover

The ATO defines GST turnover as total business income, not profit, less certain listed amounts. The business.gov.au page makes the same point in its own words: GST turnover is business income, excluding certain sales, and not profit. Its example is a business with $80,000 in sales and $40,000 in profit. The measure is $80,000, which is over the threshold, even though only half of it was kept.

Costs do not appear in either column. Because the measure is income and not profit, what the business spends is not subtracted, and a business with high costs and a thin margin can still be over the line.

The same logic holds for any pair of businesses. Take two hypothetical sole traders who each invoice $80,000 over 12 months. One spends $70,000 on stock and materials and keeps $10,000. The other spends $20,000 and keeps $60,000. Their profit differs six-fold, and their GST turnover is identical, so the threshold treats them identically. (Both sets of figures are invented.)

Three other points from the same guidance complete the picture.

• The threshold is $75,000 for a business and $150,000 for a non-profit organisation.
• GST group turnover includes the turnover of group members, so an entity inside a group does not measure itself in isolation.
• Taxi and limousine travel, including ride-sourcing, requires registration regardless of turnover.

Two tests, run every month

The ATO describes two measures, and meeting either one triggers the requirement.

1. Current GST turnover is the current month plus the previous 11 months.
2. Projected GST turnover is the current month plus the next 11 months. The test is whether it is “likely to be” at or above the threshold.

The first is a record. The second is a judgement, which is why it can bite earlier. Neither is a financial-year total, and neither resets on 1 July. The ATO’s advice is to check each month, which follows from the structure: a new month drops the oldest from the current figure and adds one to the projection.

The financial year matters for tax returns, but it plays no part in this measure. Consider a hypothetical business whose busiest months fall in May, June, July and August. A financial-year reading splits that busy stretch across two years, and each year may look modest on its own. The rolling window ignores the 30 June boundary and counts the four busy months together, so the picture can look very different.

On timing, the two sources differ slightly in wording. The ATO states that registration is due within 21 days of GST turnover exceeding the threshold. The business.gov.au page states 21 days from becoming aware that turnover will exceed it. The shared practical advice is the same: check every month, not at the end of the year. The business.gov.au page adds that a new business should register if it expects to reach $75,000 in its first year.

Other thresholds exist for other purposes, so a figure seen elsewhere in small business tax material may not be this one.

A worked example, month by month

The figures below are hypothetical. Every income figure is invented, the method is the ATO’s, and the example is not drawn from any real business.

A sole trader earns $3,500 a month, excluding GST, in months 1 to 6, and $5,500 a month in months 7 to 12. Income then rises: $9,000 in month 13, $9,500 in month 14, $10,000 in month 15 and $10,500 in month 16. If months 1 to 12 were a financial year, the total would be $54,000, below $75,000.

The current column moves by one rule. Each month the oldest month drops out of the window and the newest enters. Between months 12 and 13, $3,500 from month 1 leaves and $9,000 arrives, so the total rises from $54,000 to $59,500. Months 14, 15 and 16 each drop another $3,500 month, which is why the current figure climbs by $6,000, $6,500 and then $7,000 as the monthly income rises. The projected column moves faster in this example because it takes the latest month’s income and repeats it forward, so a single higher month changes the whole forecast.

The projected test is met from month 13, three months before the current test. In month 13 the trader has not yet reached $75,000 in the past 12 months, and has still passed the forward-looking test. A person reading the rule as “$75,000 a year” would see no reason to act until month 16.

What the figures exclude:

• Incomes are before GST.
• The projected column assumes the month’s income repeats. The ATO says “likely to be”, which is a judgement the owner makes, and this assumption is a simplification of it.
• Sales of a capital asset and sales made only because the enterprise is ending are left out of the projected test.
• No tax, cost or profit appears, because none counts.

What if turnover was high for one stretch only?

The ATO addresses this directly. Even where current GST turnover is at or above the threshold, a business does not have to register if its projected GST turnover will be below it.

The projected figure has its own exclusions. It leaves out the sale of a capital asset, and it leaves out sales made solely because the business is ceasing or substantially reducing its activity. A one-off sale of a business vehicle, for example, is the type of income that the capital asset exclusion describes.

Two features of the wording are worth keeping in view. The first is that the projected test asks whether turnover is “likely to be” at or above the threshold, so it is a judgement about the coming 11 months and not a mechanical sum. The second is that the relief runs in one direction only: it allows a business with a high current figure to stay unregistered when the forward view is lower, and it says nothing in favour of a business whose current figure is low but whose forward view is high. In the worked example above, the projected test is the one that fires first.

The ATO page does not work through the month in which a one-off lands, or how the current and projected measures interact across that month. That gap is real, and this article does not fill it. A business in that position should take the specific facts to a registered tax agent.

If you miss it

The ATO states that a business required to be registered that is not registered may have to pay GST on its sales from the date it was required to register. That applies even where no GST was included in the price charged. Penalties and interest may also apply. The ATO page states that backdating of a registration is limited to 4 years.

The practical consequence is a cost that may be hard to recover from customers after the event, since the sales were priced without GST. For that reason, the monthly check matters more than the annual one.

Registering before you have to

Below the threshold, registration is optional. The ATO page states that a business that registers voluntarily should generally stay registered for at least 12 months. The business.gov.au page lists the obligations: include GST in prices, claim credits, and lodge activity statements.

There is a fair case for registering early, and it deserves to be stated. Some owners register at the start so that they can claim credits on start-up costs, or because it presents the business as established to commercial customers. Others prefer to wait, in order to avoid the activity statements and the need to charge GST. Both views are legitimate. Which suits a given business depends on its customers, its costs and its other obligations, and the decision is one for the owner and the owner’s accountant.

Registration also brings the lodging duty with it. A business that registers early and then does not lodge its activity statements has taken on an obligation it is not meeting. The two pages state the obligation and not its consequences, so this article states only the obligation.

What the threshold does not change

Four points from the guidance hold whatever the figures show.

1. The measure stays turnover. The business.gov.au example of $80,000 in sales and $40,000 in profit is measured at $80,000.
2. The window stays rolling. The worked example above crosses the threshold in month 13 and month 16 without any financial year being complete.
3. A group is measured as a group. GST group turnover includes group members, so a single member’s figure is not the test.
4. Some businesses sit outside the threshold altogether. Taxi and limousine travel, including ride-sourcing, requires registration regardless of turnover.

None of these points tells a particular business what to do. They set out what the test measures, and the registered tax agent or the ATO applies it to the facts.

Run the Numbers Monthly

One step covers most of it: add this month to the previous 11, then add it to a forecast for the next 11, and compare each total with $75,000. If either reaches it, check the ATO’s page, and speak to a registered tax agent about the 21 days.

Sources: Australian Taxation Office, Registering for GST, version last updated 23 May 2025 (https://www.ato.gov.au/businesses-and-organisations/gst-excise-and-indirect-taxes/gst/registering-for-gst); business.gov.au, Register for goods and services tax (GST) (https://business.gov.au/registrations/register-for-taxes/register-for-goods-and-services-tax-gst)

Three common beliefs about engine coolant do not hold up against what the motoring clubs say: that plain water is an acceptable substitute, that a steady temperature gauge shows a healthy system, and that coolant either never needs changing or changes on a fixed calendar. In each case the same authority settles the question. It is the vehicle maker’s owner’s manual, which RACQ, RAA and RACV all point the reader towards, with a mechanic for any remaining doubt.

What the cooling system does

Engine coolant circulates through the engine, the radiator and the hoses, moving heat out of the engine. That description is all the detail the argument below requires. It carries no temperature figures, because a number that is right for one engine is not right for another.

Three myths, set against the evidence

The second row separates two different things. A temperature gauge reports the engine’s temperature, and a level check reports how much coolant is in the system. RACQ treats the level as something to watch in its own right, which is why a normal gauge reading does not close the question.

The third row explains why this article gives no change interval. Any figure quoted without a make, model and engine attached would be a guess. The calendar is a convenient proxy for a service schedule. It is not one.

There is a fair point on the other side of the first row. Where a driver is stranded with an empty system, water to get the car off the road is better than driving on with nothing, and that is this article’s own position, not a rule quoted from a club. What matters is the step that follows: have the system checked, because the water has not corrected whatever lost the coolant in the first place.

The three rows read together

Taken together, the rows describe a sequence and not three separate rules. The level is checked on a cold engine, at intervals, against the marks on the reservoir. A level that keeps falling is reported to a mechanic, because coolant loss is the thing RACQ says to have checked immediately. The fluid that goes back in is the one the manual names, and the manual’s schedule says when it is renewed. Water enters this sequence in one place only, as a stopgap to get off the road.

A hypothetical case shows how the rows interact. (Everything in it is invented for illustration.) Take a driver whose temperature gauge has always sat in the middle and who has never opened the bonnet. The gauge reading says nothing about the level, so the level is unknown. If that driver tops up with water after noticing a low bottle, the system is fuller, but the cause of the loss is unaddressed, and the coolant that remains is diluted by an unknown amount. The gauge reading would not have told the driver any of those three things.

How to check the level

RAA advises checking the coolant only when the engine is cold, because otherwise liquid can spurt out and burn. The check itself is a look at the plastic flow bottle, where the coolant should sit between the low and high lines, about halfway between them. RACQ adds that the owner’s manual explains how to do this for a particular car.

Signs worth a mechanic’s attention

The sources support a short list, and only that:

• a rising temperature gauge or a warning light
• coolant loss

Neither is a diagnosis. Both are reasons to have the car looked at, and RACQ advises having any coolant loss checked immediately.

What the sources settle, and what they leave to the manual

What these figures leave out

The only measurement in this article is the “about halfway” position of the fluid between two marks, attributed to RAA. It excludes the mix ratio of coolant to water, the type of coolant an engine tolerates, the change interval, and whether a particular product suits a particular engine. All four are specific to a vehicle, and none can be read off an article.

It follows that the sources do not rank one coolant over another and neither does this piece. A reader comparing products should compare them against the manual’s specification, and a mechanic or the service booklet can confirm it.

What the manual decides

The owner’s manual decides the type, the mix and the interval, and it explains how to check the level on that car. Water is for getting off the road, a steady gauge is one reading and not a verdict, and the calendar is a guess at a schedule the maker has already written down.

Sources: RACQ, “What to do if your engine overheats” (https://racq.com.au/articles/drive/2023/1/what-to-do-if-youre-engine-overheats); RAA, “Can your vehicle handle the heat?” (https://samove.raa.com.au/can-your-vehicle-handle-the-heat/); RACV, “Easy DIY car maintenance tips and safety checks” (https://www.racv.com.au/royalauto/transport/cars/easy-car-maintenance.html)