Super Unleaded?

Question

I hjave a BMW 335 and wondered if there is any real benefit to using Super Unleaded (98) rather than normal 95.

I have read that it only really helps high performance cars (Astons, Ferraris etc) and that there's no benefit to normal engines at all.

But, I wonder where the line is that it starts giving higher performance as my car is pretty fast (5.6s 0-60), but I don't want to pay an extra £5 per tank for no/negligable benefit.

Thanks.

Just a note that the manual says its can run on either, but doesn't give a preference nor any advantages

Answer 1

Higher octane does not help cars designed to run on regular fuel. Compression ratio is the key higher compression engines will detonate regular and burn premium fuel. That detonation will eventually cause valve and piston damage. Turbo/supercharged charged petrol Gasoline engines almost always want "the good stuff" Holden Manaro GT, I drive (Pontiac GTO) uses a 10 to 1 compression ratio engine and will not run on lower grade fuel. Nissan Maxima Murano's 350z and some Altimas Fuel door says for max performance use premium. And with approx 2 to 3 more miles a gallon the additional cost is actually about the same per tank full for the additional distance.

Answer 2

I have used it in 2 cars and a motorbike. Proves to give smoother running, a little more power and a few extra mpg but no where near enough to off set the extra cost. Since your car has to use it you have no choice so why be concerned. "One of our users commented that using higher octane fuel than your engine requires actually gives no benefit and may be a waste of money. This is because virtually NO engines require 98 RON over 95, and the market for 'super' fuels seems to be based on people's misunderstanding of octane ratings and the placebo effect of filling up with 'more powerful' fuel - making motorists think their engine is running better in some way. What do the fuel companies say then, to justify the "increased power" claims for the super grade fuels? Some companies say that while all fuels contain cleaning additives, 'super' fuels contain more or better detergents to keep the injectors cleaner than standard fuel. Others say the fuel is a few percent denser which gives slightly more power per litre. These benefits may be marginal though in comparison to the extra cost involved so it is worth ensuring that your engine will actually benefit before filling up. Some engines actually do need higher octane fuel, such as race engines with very high compression and some turbocharged engines, such as the import version of the Nissan Skyline. Also, a few vehicles, such as the new BMW K1200R motorbike, can sense knock and adjust their engine tuning to take advantage of higher grade fuels. Another user commented that the 2004 BMW 330 also does this, according to the driver's handbook it makes 231 BHP on 98 octane and 221 BHP on 95. This ability is apparently widespread amongst German performance cars using Bosch / Siemens electronic engine controls".

Answer 3

Check with a BMW dealer,if you car was designed to run on Unleaded then there is no need to use the 98, the 98 is mainly for cars that are old and designed for what used to be 4 star or super

Answer 4

Higher octane ratings only really benefit cars with very high compression ratios as the electronics would retard the spark to stop pre-ignition and knocking.
I do not think it would be any advantage in your car but have a look at the handbook they usually make comments on which fuel is best.
RoyS

Answer 5

Super unleaded has a higher octane rating, that's all - it's the equivalent of the old 4 star. Whether you need it depends on the compression ratio of the engine, not how powerful it is.

Answer 6

The only way to see if there's a difference is to try a few tankfuls of super and see if you notice the difference.
Surely to God if you can afford a BMW 335 you won't notice an extra fiver per tank!

Answer 7

umm, 5.6s is pretty slow. I think my corolla will do 0-60 in that time.

The octane rating of gasoline affects how much the mixture can be compressed (and therfore heated) before it will spontaneously combust. Higher octane fuel can be compressed more before it autoignites. Therefore there is no benefit to running high-octane fuel in a vehicle that doesn't require it.

Vehicles that require high-octane fuel are those with high-compression engines, say, greater than 9:1. You need to find out what the compression ratio is on your engine, then ask a mechanic or someone at autozone what would be the required octane rating for that engine.

If you run low octane fuel in a high-compression engine, the engine will start knocking because the fuel begins to combust before it's supposed to.

Answer 8

I really don't think that using the super unleaded will make the slightest bit of differance to your car or the preformance, but it will make a differance to your wallet,so stick to normal or Premium,other wise your just lining the companys pockets even more.Good Luck Mark, Maxine.

Answer 9

Iv'e been using it in my Volvo XC90 for about six months and the car runs better with increased fuel efficiency of about 7% so far, so i find it actually cheaper to use. The only way is to try it and see if it works for you too. Happy motoring and Christmas!

Answer 10

If you are doing a lot of motorway driving - it is more cost effective.
Also the car becomes more responsive.
That's what I have found anyway!