Is regular unleaded better than super unleaded?
12-31-2005, 06:16 AM
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My Ride: 2006 530xi. Deep green with beige interior. 6 speed manual. Premium package.
This is from my knowledge of GM cars - so this may not apply to BMW's, but...
The range that the computer shows is the miles per gallon times the amount of fuel. Has little to do with what fuel you use for one tank. There are some measurements that the car uses that do incorporate how much fuel is used becasue the instantaneous mileage is calcualted by the computer and this uses how much fuel goes throught the injuectors. So theoretically if you use a different octane gas you injuectors will use a different amount of fuel and give you a different calculation.
But the most important factor in calculating fuel mileage is what is the previous mpg - if you reset it and go on a long highway trip you will see huge numbers and if drive in the city small numbers, but after a while you will get an average - and depending on you average your range will vary
So everyone in a BMW does not have the smae range show on the computer
People who do a lot of highway driving have a longer range
As far as fuel - in the US usually on 3 choices 87, 89, 93 octane - BMW recommends 91 - So I use premium
Why does Europe have more octane? Is there different emissions issues or what?
The range that the computer shows is the miles per gallon times the amount of fuel. Has little to do with what fuel you use for one tank. There are some measurements that the car uses that do incorporate how much fuel is used becasue the instantaneous mileage is calcualted by the computer and this uses how much fuel goes throught the injuectors. So theoretically if you use a different octane gas you injuectors will use a different amount of fuel and give you a different calculation.
But the most important factor in calculating fuel mileage is what is the previous mpg - if you reset it and go on a long highway trip you will see huge numbers and if drive in the city small numbers, but after a while you will get an average - and depending on you average your range will vary
So everyone in a BMW does not have the smae range show on the computer
People who do a lot of highway driving have a longer range
As far as fuel - in the US usually on 3 choices 87, 89, 93 octane - BMW recommends 91 - So I use premium
Why does Europe have more octane? Is there different emissions issues or what?
12-31-2005, 06:20 AM
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Originally Posted by dgjk' post='217642' date='Dec 31 2005, 10:16 AM
Why does Europe have more octane? Is there different emissions issues or what?
http://www.stretcher.com/stories/01/010226m.cfm
12-31-2005, 07:01 AM
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Originally Posted by ImolaRedM' post='217634' date='Dec 31 2005, 02:50 PM
To get the best performance use what the manual states. Turbocharged engines don't benefit from the higher octane. However, generally, engines with higher compression ratios will be more efficient with higher octane fuel.
12-31-2005, 07:15 AM
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Here's some good information.
http://www.stanford.edu/~bmoses/knock.html
Also, while I said tubo's don't need higher octane they're generally attached to engines with higher compression anyway. Remember that a turbo is just an air pump (like an engine). It will help your engine breath better. The turbo itself has little to do with the actual detonation of the air-fuel mix.
http://www.stanford.edu/~bmoses/knock.html
Also, while I said tubo's don't need higher octane they're generally attached to engines with higher compression anyway. Remember that a turbo is just an air pump (like an engine). It will help your engine breath better. The turbo itself has little to do with the actual detonation of the air-fuel mix.
12-31-2005, 08:04 AM
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Originally Posted by Taz' post='217589' date='Dec 31 2005, 12:42 PM
I have an E60 530i SE and am in the UK. I've been filling up with Shell Optimax petrol (super ulneaded, 98-RON) since I got the car. However, due to a recent well-publicised fire in the South-East of England, there is a shortage of petrol at some petrol stations.
So, I filled up with regular unleaded (95-RON) and my range indicator is now showing more than 400 miles. I rarely get more than around 280 miles with a full tank of Shell Optimax. How can regular unleaded potentially provide a greater range?
So, I filled up with regular unleaded (95-RON) and my range indicator is now showing more than 400 miles. I rarely get more than around 280 miles with a full tank of Shell Optimax. How can regular unleaded potentially provide a greater range?
With higher RON you should get better milage and more HP!
This is the reason why US engines rate less HP than EU engines,
in US the RON's are not more than a bit over 90.
12-31-2005, 09:04 AM
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My Ride: I have a 2004 E60. It was registered in January 2004. It's a Black Sapphire 530i SE with a few options:
- Auto-dim interior + folding exterior mirrors
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The reason i'm a bit perplexed is that I had a Porsche Boxster before and I always put super unleaded (Shell Optimax, 98-RON) into that as that was the recommended octane rating. With that I got the best performance and the highest MPG.
I then traded in my Boxster and got my 530i. I just carried on using Shell Optimax until yesterday. As far as I know, the range computer uses a rolling avergae based on the fuel consumption in the last 20 miles of driving (or something similar). It could have been that I was driving at a steady speed just before I filled up yesterday. Hence, after I filled up the computer told me that I had more than 400 miles to go.
I did 22 miles of town driving today and the range is now below 340 miles. So the computer is adjusting the range as i'm driving less efficiently. That bit I can cope with and understand.
However, my car actually feels more responsive and smoother with regular unleaded (95-RON)! By the way, in the UK regular unleaded (95-RON) is actually known as 'Premium Unleaded'. Any petrol over 97-RON is known as Super Unleaded.
My conclusion so far is that the car is more suited to normal unleaded fuel than super unleaded.
I then traded in my Boxster and got my 530i. I just carried on using Shell Optimax until yesterday. As far as I know, the range computer uses a rolling avergae based on the fuel consumption in the last 20 miles of driving (or something similar). It could have been that I was driving at a steady speed just before I filled up yesterday. Hence, after I filled up the computer told me that I had more than 400 miles to go.
I did 22 miles of town driving today and the range is now below 340 miles. So the computer is adjusting the range as i'm driving less efficiently. That bit I can cope with and understand.
However, my car actually feels more responsive and smoother with regular unleaded (95-RON)! By the way, in the UK regular unleaded (95-RON) is actually known as 'Premium Unleaded'. Any petrol over 97-RON is known as Super Unleaded.
My conclusion so far is that the car is more suited to normal unleaded fuel than super unleaded.
12-31-2005, 09:04 AM
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Originally Posted by Ricracing' post='217677' date='Dec 31 2005, 12:04 PM
This is the reason why US engines rate less HP than EU engines,
in US the RON's are not more than a bit over 90.
in US the RON's are not more than a bit over 90.
Here's what I believe to be the real reason for the difference. BMW got in a little bit of hot water with the E39 M5 over this.
http://en.wikipedia.org/wiki/Talk:Horsepower
Read the part about ...
Code:
Horsepower is a complicated issue. Part of it is to do with there being two definitions of horsepower: Imperial horsepower (1 hp = 33,000 ft?lbf?min-1) and German pferdstarke (nowadays defined in terms of SI units: 1 PS = 75 kp?m/s = 735.49875 W). The two thus differ slightly; by my calculations, 1 hp = 1.014 PS. Fairly often, in non US markets, a power rating is given in 'hp' in English-language publication, but the values are actually 'PS' unconverted. This is even sometimes true for British or American products sold on the world market.
12-31-2005, 09:51 AM
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Octane rating basically tells you how much pressure the fuel can withstand before combusting spontaneously. Higher octane = higher compression.
If the fuel combusts too early, then your engine will knock.
If you can use lower octane without engine knocking, then go for it.
Personally, I won't risk it. The price difference here in the USA isn't that much.
If the fuel combusts too early, then your engine will knock.
If you can use lower octane without engine knocking, then go for it.
Personally, I won't risk it. The price difference here in the USA isn't that much.
12-31-2005, 10:18 AM
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I just wish I was paying what you yanks do for petrol. Screw the octane rating 
Just to stress the point I am paying $6.00 a gallon for 95 Octane petrol here in the UK (?3.50 a gallon) !!!!
Just to stress the point I am paying $6.00 a gallon for 95 Octane petrol here in the UK (?3.50 a gallon) !!!!
12-31-2005, 10:19 AM
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My Ride: 2006 BMW M5, Silverstone with black extended leather, brushed aluminium trim, Nav Pro, Logic 7, PDC, 35 % tint.
I think this has been covered before. The ocatane ratings in N. America and England are different, so you can't compare the numbers. I think you should just use what BMW recommends, which is 91 in N.A. What you need is written in the fuel cap.