Mmmmmm high octane...

[Dan in NZ]

I've always filled my car up (M20 engine 525) with regular (91 octane), but just to see if there was any difference, I filled the car from almost empty with 98 octane BP Ultimate. $112 for 72 litres, ouch. I'm sure it runs smoother/quieter/more powerful compared to regular... Also noted, when I blip the gas in neutral, it revs up freely and smoothly. With 91, a blip on the throttle would sometimes miss a beat as it revved. Liters/100km dropped a bit too.

This could always be placebo effect of course, but I'll try a few more tankfulls and see how it goes. I had heard that if an engine is designed to run on regular, there's no benefit in using premium, it just costs more.

Has anyone else experimented with using high octane fuel? Thoughts?

Don't forget that different parts of the world use a different octane scale before we start comparing numbers...

[Interceptor]

Has anyone else experimented with using high octane fuel? Thoughts?
If anything, high octane fuels are usually cleaner and contain detergents for cleaning fuel injection systems. They also contain less sulfur.

[Alexlind123]

My 535ia specifies UNleaded Premium only.

[mikell]

Could be the detergent content - and, while on the fuel subject - what about the "name brand vs no-name" fuel question? I've seen some hype lately about "prime fuel" or something that says that the big name brands (Shell, Chevron and a couple of others) are superior 'cos they're nicer to injectors. Problem is, they are also significantly more expensive (sometimes 10 + cents per gallon) than the no-name brands in my area. I figure the difference is the money the majors invest in advertising. Any input? Do I have to switch to the high price flavor? I mean, my car's got 200k miles on it and I have used pretty much the best priced fuel I could find for all these years, with an occasional bottle of fuel treatment. But, I always use premium grade - maybe that's the difference.

[Jay 535i]

I think it's probably the detergents and other additives that are improving your car's performance, rather than the extra octane.

I'm certainly no shill for the oil companies, but I do believe that the billions of dollars behind Shell, Chevron et al. do enable them to do the R&D that leads to better fuels, compared to a no-name brand fuel.

A couple of years ago, I remember, CAR magazine did a test where they ran a few cars for several thousand miles with a variety of fuels, then removed the cylinder heads and took pictures. The cars run with Shell Optimax were visibly WAY cleaner inside than cars run with cheap gas, or even lesser grades of Shell.

On my 1986 Toyota, I use Optimax for one in three tanks, to keep it clean, and whatever's cheap the other two times. In my BMW, I always use premium (because of the EAT chip) and prefer Shell whenever possible, because of that article in CAR. It was really convincing, and CAR is certainly objective.

[Jay 535i]

My 535ia specifies UNleaded Premium only.

In 1990 terms, that probably equates to today's middle-of-the-road fuels. Back then, there was nothing available resembling today's premium fuels.

[Zeuk in Oz]

I've always filled my car up (M20 engine 525) with regular (91 octane), but just to see if there was any difference, I filled the car from almost empty with 98 octane BP Ultimate. $112 for 72 litres, ouch. I'm sure it runs smoother/quieter/more powerful compared to regular... Also noted, when I blip the gas in neutral, it revs up freely and smoothly. With 91, a blip on the throttle would sometimes miss a beat as it revved. Liters/100km dropped a bit too.

This could always be placebo effect of course, but I'll try a few more tankfulls and see how it goes. I had heard that if an engine is designed to run on regular, there's no benefit in using premium, it just costs more.

Has anyone else experimented with using high octane fuel? Thoughts?

Don't forget that different parts of the world use a different octane scale before we start comparing numbers...

Have always used the highest octane in mine - either Shell Optimax or BP Ultimate so cannot compare with low octane.

Do so due to the injector cleaners etc in the dearer fuel. Certainly no complaints.

[AllGo'n'Show]

I wish I had 98 up here to fill my baby up with.