Do You Actually Need Octane Booster? An Honest Answer
If you've spent any time in classic car forums, you've seen the debate: someone posts a photo of a bottle of octane booster in their glovebox next to a paper road map, and the comments split into two camps immediately. One side swears by it. The other says it's snake oil for a problem that doesn't exist anymore.
The truth, as usual, sits in the middle — and it depends entirely on what's under your bonnet.
We're going to lay out exactly who benefits from carrying a bottle of OlioClassico's octane booster on a touring drive, and — just as importantly — who's carrying dead weight and peace-of-mind theatre instead.
The compression ratio conversation nobody has
Most 1970s sports cars — your MGBs, TR6s, early 911s, Alfa twin-cams in standard tune — were built around compression ratios in the 8.5:1 to 9.5:1 range. Crucially, they were engineered for the fuel that was actually in the pumps in 1974, which was typically in the 91–97 RON range. Having a 98 octane premium option at many petrol stations is a modern convenience, not something these engines were ever designed to depend on.
What that means in practice: if your engine is in factory spec, and you fill up with standard 91 RON unleaded at a rural station because that's all they had, your car is very likely running on fuel similar to — or barely below — what it left the factory expecting. You are not doing it harm.
Where this stops being true
The picture changes if any of the following apply to your car:
It's been modified. Higher-compression pistons, a hotter cam, advanced ignition timing, or a warmed-over head from a previous owner all push the octane requirement up, sometimes well past what the original spec sheet says.
It's a factory high-compression variant. Some Alfa twin-cams, certain Lotus twin-cam engines, and higher-state-of-tune Porsche flat-sixes ran 10:1 or higher from the factory and were genuinely engineered around 'super' fuel of their era.
It already pings on your usual fuel. If you've heard light knock on your regular tank at home, a lower-octane country pump will make it worse, not better.
You're about to load the engine hard. A mountain pass, a fully loaded car, sustained high-rev touring, or hot weather all increase detonation risk regardless of how mild your engine is.
If you fall into any of those categories, an octane booster isn't a gimmick — it's a genuinely useful bit of kit to carry, and the math backs it up: a 2.5 L dose in a 50 L tank (roughly a 5% blend) typically lifts RON by somewhere in the region of 1.5 to 2 points. That's not a transformation, but it's often the difference between a car that pings under load and one that doesn't.
What actually happens if you don't have it
This is the part sales copy tends to skip over. If you're touring a bone-stock, standard-compression classic and you hit a station with nothing but 91 RON:
You might hear light pinking under hard acceleration or on a long uphill pull in a high gear.
Backing off the throttle, dropping a gear, or (if you're handy under the bonnet) retarding the timing 2–3 degrees resolves it.
A single tank of lower-octane fuel will not damage your engine. Sustained heavy detonation over many hours could genuinely hurt pistons and rings — the odd bit of light knock on a touring drive is not that.
In other words: for the majority of stock classics, the "emergency" that the booster solves is mostly theoretical.
So who should actually buy it?
Octane booster earns its place in the boot if —
You know your specific car pings on standard fuel — you've heard it happen, not just worried it might.
Your engine has been modified from factory compression, cam, or timing spec.
You're planning a route with sustained high-load driving — alpine passes, spirited mountain roads, or anything that keeps the engine under load for extended periods.
You're driving a factory high-compression variant that was genuinely built around premium-grade fuel.
If none of those apply, you're likely better served by keeping the money and the boot space, and simply backing off the throttle if you hit a rough patch of pinking on a rural fill-up.
The honest bottom line
A bottle of octane booster is not a universal necessity for classic car touring — for a bone-stock 1970s sports car in original tune, it's a nice-to-have insurance policy at best. But for modified engines, factory high-compression variants, or cars with a known pinging issue, it's a small, legitimate safeguard against a real risk.
The best thing you can do before your next tour isn't to blindly pack an octane booster — it's to actually know your engine's compression ratio and history well enough to know which category you're in. If you're not sure, ask in the forums, check with a marque specialist, or have a mechanic look over your ignition timing. That fifteen-minute conversation will tell you more than any bottle on a shelf.
OlioClassico's octane booster is a genuinely useful product for the enthusiasts who need it. We'd just rather you carry it because you know you need it, than because you're not sure and it felt safer to have it along.