Fuel for a Japanese import: what octane it was built for, and what you'll find at home

A car that has spent its life in Japan has been filled with Japanese petrol. Japan's industrial standard sets two grades: regular at 89.0 octane or more, and premium (haioku) at 96.0 octane or more. Many Japanese performance cars were specified for premium. Once the car is in the UK, Australia or New Zealand, the pumps are different, and in the UK and Australia some of what's sold contains ethanol.

None of this is something a listing photo shows, and it isn't something we check at a dealer. It's a question to settle before the car arrives.

What the car was built for

The maker's own records say which grade a car was specified for. Nissan's FAQ on the R34 Skyline GT-R (BNR34), for example, lists its fuel as unleaded premium. The owner's manual and a label inside the fuel filler flap usually say the same, in Japanese: "mu-en puremiamu" (unleaded premium) or "haioku" (high octane).

If the listing doesn't say, ask the seller for a photo of the label inside the fuel flap.

When I owned my R33 GT-R and my EP3s, they always got premium. For a car built for Japanese premium, my view is that if you fill it with the highest-octane petrol on sale, I don't think you'll have a problem. That's my view, not a promise about any particular engine, and the number on the pump is what to check: the table below shows it isn't the same everywhere.

What you'll find at the pump

Country	What's sold	Ethanol	What the government says
United Kingdom	Standard grade 95 octane (E10). The super grade is 97+ octane (E5)	Up to 10% in the standard grade, up to 5% in the super grade	All cars built since 2011 are E10-compatible. Some models, particularly from the early 2000s, and older and classic cars may not be. If your model isn't in the government's E10 checker, check the manual or ask the maker, and if in doubt use E5
Australia	Two grades in the fuel standard: 91 and 95 octane	Up to 10% in petrol	The standard sets the minimum octane for each grade, and its higher grade is 95. That's below Japan's 96.0 minimum for premium, so check the number on the pump rather than the name
New Zealand	Three grades: 91, 95 and 98 octane	―	Engines built for high-octane fuel have their timing set for it. The wrong octane can cause knocking and engine damage, or lower efficiency, or both

Octane numbers here are research octane (RON), the same scale as Japan's. US pumps use a different number: the average of research and motor octane, under the FTC's rule. A US "91" or "93" isn't the same scale, so don't set it against the figures here.

What the makers say about a lower grade

Nissan's own FAQ answers the question for its premium-spec cars: if premium isn't available, regular can be used, but the fuel economy and acceleration the car was built for may not be there, so Nissan doesn't recommend it. It adds that the R35 GT-R can't use regular at all, and that owner's manuals from the early 1990s and before may not say which fuel to use.

On knocking, Nissan's FAQ says it's more likely with low-octane petrol. Light knocking at low revs for a short time does no structural harm, it says, but strong knocking or knocking at high revs can burn pistons and rings or blow a head gasket. A knock sensor detects knocking and has the engine's computer adjust the ignition timing to stop it.

JAF, Japan's motoring organisation, says recent premium-spec cars will rarely break straight away on regular, but it can cause some faults, so stick to the specified fuel. Neither says how a particular car from the 1990s behaves, or whether it has a knock sensor. That's for its own manual or a specialist.

Where Japanese imports get caught out

A Japanese-market model that isn't on the UK checker. GOV.UK's checker lists cars by maker and model. A model sold only in Japan may not be on it. GOV.UK's advice for an unlisted car is the manual or the maker, and E5 if in doubt.

Early-2000s cars. GOV.UK names "some specific models, particularly those from the early 2000s" as possibly not E10-compatible. Those are also the years now reaching the 25-year lines in the US and Australia: a car built in 2002 reaches them during 2027, depending on its build month. Our age line date checker works out the date for any build month.

A premium-only car on regular. In Australia and New Zealand, the lowest grade is 91 octane, well under Japan's 96.0 for premium. The UK's standard grade is 95. What a given engine does on a lower grade is a question for its maker or a specialist, not for us.

What this page can't tell you

• Whether your car can run on a particular fuel. That's the maker's answer, from its manual or its records for that model.
• Whether a car has been retuned for a different fuel. We photograph what's fitted and can be seen; we don't judge engine tuning.
• How a car runs. We don't test drive or connect diagnostic equipment.

The fuel the car was built for is written down. The state of the engine bay isn't. Send us the listing and tell us what to look at.

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Written by Yoshiaki Sagara, a paintless dent repair and detailing technician in Japan. He looks at cars for overseas buyers through Ninja Desk Japan. About us

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