I read about MOT problems with 95 RON and no MOT problems with 98 RON. Discussing this with my son (pistonhead) he told me that filling the Plus Four always with RON98 would be a good idea. So i asked AI what they think about it:
Fuel choice is especially important with a B48 (BMW's 2.0 turbo 4-cylinder).
The B48 is designed for a minimum of 95 RON, but it's fully compatible with 98 RON (Super Plus). It automatically adjusts via knock sensors and engine management.
Below are the real pros and cons — without the marketing nonsense 😉
✅ Advantages of always using 98 RON
1️⃣ Better knock resistance (more safety under load)
98 has a higher octane rating → less chance of knocking/pinging under:
High turbo pressure
Warm engine
Sporty driving
Autobahn/full load
The B48 can therefore:
provide slightly more ignition advance
deliver more stable power
➡ Especially useful if you often drive hard.
2️⃣ Slightly better performance (but limited)
The gain is small, but measurable:
Slightly smoother throttle response
Possibly a 2–5 hp difference
Slightly more consistent performance in warm weather
You'll hardly notice this during normal, relaxed driving.
3️⃣ Possibly slightly cleaner combustion
In many countries, 98 contains:
Less ethanol (often E5)
Sometimes more additives
This can:
Provide slightly less fouling of injectors
Provide slightly more stable combustion
However: the difference isn't dramatic.
❌ Disadvantages of always using 98
1️⃣ Higher cost
In Belgium/the Netherlands, usually:
8–15 cents more expensive per liter
Over the year, this can be €150–€300 extra, depending on your mileage.
2️⃣ No significant benefit during normal use
If you:
drive calmly
don't have any tuning
don't put a heavy load on it
then the B48 will run perfectly at 95 and you'll hardly notice any difference.
3️⃣ No "extra power" without tuning
The ECU of a standard B48 isn't aggressively tuned.
98 doesn't provide "magical extra power" unless:
you have Stage 1 tuning
or a performance map
🔧 When is 98 really recommended?
✔ Sporty driving
✔ Long highway journeys at high speed
✔ Hot summer days
✔ Tuned engine
✔ If you want maximum engine safety
📊 Summary
Use Best choice
Quiet commuting 95 is sufficient
Mixed use 95 or 98
Sporty / Autobahn 98 recommended
Tuned Always 98
🎯 My technical opinion
The B48 is a modern turbo with high compression (11:1).
It runs a little "happier" at 98, but it's not essential.
If you plan to keep the car for a long time and the price difference doesn't bother you → 98 is never a bad idea.
But 95 definitely doesn't harm the engine.
