Fuel experiment - The Unofficial BMW M5 Messageboard (m5board.com)

Rob Plummer · 10th November 2005, 10:55

I've just confirmed what I always thought.

Tried normal unleaded for my last two tankfuls.

Couldn't feel any difference (unfortunately, 90% of my driving is at a sedate speed), but the fuel economy dropped immediately by 2mpg.

My maths is terrible, but I've always reckoned that the extra cost for Optimax is outweighed by the better economy it gives you.

If you say an average fill up is 75litres? What's the price difference between normal unleaded and Optimax? About 5p/litre on average?

So if you say it costs you an extra £4 every time you tank it, but you get roughly an extra 30-35 miles out of the tank, then it CAN be justified financially (apart from the obvious benefits of better fuel).

Are my maths correct someone?

Jon Baker · 10th November 2005, 11:34

Quote:

Originally Posted by Rob Plummer

I've just confirmed what I always thought.

Tried normal unleaded for my last two tankfuls.

Couldn't feel any difference (unfortunately, 90% of my driving is at a sedate speed), but the fuel economy dropped immediately by 2mpg.

My maths is terrible, but I've always reckoned that the extra cost for Optimax is outweighed by the better economy it gives you.

If you say an average fill up is 75litres? What's the price difference between normal unleaded and Optimax? About 5p/litre on average?

So if you say it costs you an extra £4 every time you tank it, but you get roughly an extra 30-35 miles out of the tank, then it CAN be justified financially (apart from the obvious benefits of better fuel).

Are my maths correct someone?

Maths are pretty much correct. 30 - 35 miles = 1.3/4 gallons = £6.50 roughly

Cyrus · 10th November 2005, 13:54

I noticed that too, better economy on 98 ron. Its very difficult to feel any performance gains at these levels of power.

Jon Baker · 10th November 2005, 15:57

Quote:

Originally Posted by Cyrus

I noticed that too, better economy on 98 ron. Its very difficult to feel any performance gains at these levels of power.

Tesco now do super unleaded at 99 ron. I am running it at the moment and can recommend it.

Cyrus · 10th November 2005, 15:58

99 ron!

IN the BMW handbook it recommends you use higher octane fuel than 95 to achieve best performance. They must have written for a reason. Were the cars mapped on 97?

How much did you pay for 99ron?

Phlem5 · 10th November 2005, 15:59

Funny that, I remember some threads suggesting poorer MPG with optimax - which seems to be the case when I use it..... does seem more responsive though, maybe the MPG's drop due to the right foot getting a little heavier.

Cyrus · 10th November 2005, 16:03

Going to try it out today, theres one at gallions reach.

Jon Baker · 10th November 2005, 16:06

Quote:

Originally Posted by Cyrus

99 ron!

IN the BMW handbook it recommends you use higher octane fuel than 95 to achieve best performance. They must have written for a reason. Were the cars mapped on 97?

How much did you pay for 99ron?

I am going to get all domestic now...but after spending over £50 on my weekly shopping I got a 5p per litre off voucher. I think the pump price was something like 92.9p, so 87.9p.

As you will appreciate it makes a lot of difference when filling the beast up from nearly empty, circa £4.25 saving.

Which reminds me....I need to get a life...!!!

Cyrus · 10th November 2005, 16:08

Quote:

Originally Posted by Jon Baker

I am going to get all domestic now...but after spending over £50 on my weekly shopping I got a 5p per litre off voucher. I think the pump price was something like 92.9p, so 87.9p.

As you will appreciate it makes a lot of difference when filling the beast up from nearly empty, circa £4.25 saving.

Which reminds me....I need to get a life...!!!

I drive my car about 5k a year so It doesnt make any difference hardly to me.

99 ron fuel.......then maybe a dyno test!

Jon Baker · 10th November 2005, 16:11

Quote:

Originally Posted by Cyrus

99 ron fuel.......then maybe a dyno test!

That would be interesting - especially a comparison to a previous dyno test on lower rated fuel.

Does anyone know if there would be a noticable difference at the dyno?