What grade gas you running in 3.0's

[JCL]

Originally Posted by accella4.4

Engine damge vs a paltry savings aside, isn't it a zero sum argument anyway? Before the X5, the Volvo R would run fine on 87 but a tank of 91 or 93 yielded more miles, so I've only run the 91 or 93 in the X. I only fill up about every 10 days, so if burning premo is an issue, I need to be looking at a bus pass.

It is not a zero sum argument, and in my case, I don't think it is a cost issue at all. Measuring from fill to fill, over several tanks, my best mileage has always been on 89. YMMV, it depends completely on the quality of fuel you have access to. I use 91 when I travel, but at home, all my vehicles get 89. I do notice a decrease in performance with 87, and so I don't use regular, since it is obvious that the ECU is retarding the timing. That is not true with 89 pump octane, in my case. Again, YMMV.

[fln8tive]

Originally Posted by JCL

It is not a zero sum argument, and in my case, I don't think it is a cost issue at all. Measuring from fill to fill, over several tanks, my best mileage has always been on 89. YMMV, it depends completely on the quality of fuel you have access to. I use 91 when I travel, but at home, all my vehicles get 89. I do notice a decrease in performance with 87, and so I don't use regular, since it is obvious that the ECU is retarding the timing. That is not true with 89 pump octane, in my case. Again, YMMV.

So there is chemically almost no difference between 89 and 91? I'm askin' not debatin'...and maybe I missed this, but the reason for 91 on the long runs is why? Fuel quality control or slightly more efficiency from a tank? I would ask, why not give a car the better stuff when it is working harder in stop & go city driving, no? Or, is 89 all the car requires? And what about sea-level driving vs higher altitude?

[JCL]

I just wonder, is it ok that I put Shell V-power (100 octane) in my 4.8 since I bought it? I think it's ok, because I asked in BMW service here in Geneva, they told that it is all right. Also he told me that its not good to go down with gasoline which has lower octane.

Originally Posted by DINANM3

Ive 100 octane in my M5 and M3 and it ran great. I was gonna put some in my X5 just for the hell of it this summer

DinanM3, you seem to be confusing RON with pump octane. The poster who asked the question is in Geneva. 100 RON in Geneva is very close in anti-knock properties to 93 pump octane in North America. Your 100 octane fuel in a road vehicle doesn't make a lot of sense, as the engine was not designed for it.

[Riyad Aliyev]

Originally Posted by JCL

DinanM3, you seem to be confusing RON with pump octane. The poster who asked the question is in Geneva. 100 RON in Geneva is very close in anti-knock properties to 93 pump octane in North America. Your 100 octane fuel in a road vehicle doesn't make a lot of sense, as the engine was not designed for it.

But i think in Geneva, V-power from shell is an 100 octane, and nothing else, because if v-power is equal to 93, (as i understood) then what is "Sans plomb 93" also which is offered in Shell gas stations?
Because if this is something that is even lower... A friend of mine has Mazda rx-8 and he puts Sans plomb 93 into his tank, and i think it wouldn't run on that if it would be something les than 93.

[JCL]

Originally Posted by Riyad Aliyev

But i think in Geneva, V-power from shell is an 100 octane, and nothing else, because if v-power is equal to 93, (as i understood) then what is "Sans plomb 93" also which is offered in Shell gas stations?
Because if this is something that is even lower... A friend of mine has Mazda rx-8 and he puts Sans plomb 93 into his tank, and i think it wouldn't run on that if it would be something les than 93.

You need to determine what the 100 V Power, and 93 sans plomb (unleaded) are in terms of RON. RON is the usual measurement in Europe. There is a 6-7 point spread between RON and pump octane, which is (R+M)/2, where R equals RON and M equals motor octane method. Again, it is not a precise conversion because it depends on the specific fuel.

I would guess that the 93 unleaded your friend uses is very close to 87 pump octane in North America. Just as with the BMW engine, a Mazda will run fine on 87 pump octane, it just may not develop all of the power it is capable of.

[DINANM3]

Originally Posted by JCL

DinanM3, you seem to be confusing RON with pump octane. The poster who asked the question is in Geneva. 100 RON in Geneva is very close in anti-knock properties to 93 pump octane in North America. Your 100 octane fuel in a road vehicle doesn't make a lot of sense, as the engine was not designed for it.

The M5 and M3 i put them in were modified not stock. The M3 was superharged. And beleive me it made a difference.
I was just saying that 100 ocatane in a stock 4.8 wont hurt it. Not sure if it will help it.

[JCL]

Originally Posted by DINANM3

The M5 and M3 i put them in were modified not stock. The M3 was superharged. And beleive me it made a difference.
I was just saying that 100 ocatane in a stock 4.8 wont hurt it. Not sure if it will help it.

DINANM3: Thanks for that. Yes, with those modifications I am sure you can use all the knock resistance you can find. My comment was that we should keep clear what the figure 100 means. Your 100 pump octane isn't the same as 100 RON.

Jeff

[crosvs]

It is a waste of money over purchasing 91, but it won't generally hurt the engine. If you have a misfire in cold weather, stop using higher octane fuel, as it can cause the misfire.

The biggest mistake made is that people assume that a higher AKI is somehow better. If you have a sufficient AKI to resist predetonation, anything else is lost. Your engine can't tell the difference.

This needs to be refined further: my understanding is that you want to use the LOWEST octane possible to which your car's computer can calibrate to prevent knocking.

Obviously, in a car without a knock sensor -- like my old Mustang -- 87 would prevent it from knocking just fine. Hence, using 91 would have actaully been bad -- carbon deposits in cats, etc -- until I added a chip recalibrating the engine for 91.

However, in our X's, I imagine the computer can calibrate itself all the way up to Euro-calibre fuels of 100 octane or so. Let's assume for sake of argument, however, that our computer could only handle up to 98 octane. Well then, I'd say put in 98 -- but do *NOT* put in 100!!

For instance: on May 10 when my Dad and I head up to Thunderhill Raceway in Willows, CA, we're going to fill upon 100 octane at the track because my understanding is that our X's *CAN* calibrate for 100.

[JCL]

Originally Posted by crosvs

This needs to be refined further: my understanding is that you want to use the LOWEST octane possible to which your car's computer can calibrate to prevent knocking.

Essentially you want the lowest octane possible at which you can get all the performance out of the engine. Ignition timing is one factor, so is compression ratio. Leaving aside internal engine mods, putting in fuel with a higher AKI than necessary will not give you any more power. If you go faster, it is only because your wallet is lighter.

Obviously, in a car without a knock sensor -- like my old Mustang -- 87 would prevent it from knocking just fine. Hence, using 91 would have actaully been bad -- carbon deposits in cats, etc -- until I added a chip recalibrating the engine for 91.

91 isn't bad, it just isn't necessary. It can be bad, but that is usually related to cold weather operation only. If you added a chip that takes advantage of the better fuel, fine. Did you also change the compression ratio?

However, in our X's, I imagine the computer can calibrate itself all the way up to Euro-calibre fuels of 100 octane or so. Let's assume for sake of argument, however, that our computer could only handle up to 98 octane. Well then, I'd say put in 98 -- but do *NOT* put in 100!!

Forget Euro-calibre fuels. Not sure what they are. In Europe, octane is measured according to a different formula. Although it isn't a precise conversion, there is approx a 6-7 point spread. So, a fuel that is 98 RON in Europe is essentially the same as a fuel of 91/92 pump octane in North American. The fuels are the same, the octane measurement is different. Let's keep using a consistent measure here, in this case pump octane. If you put a better fuel in than the 91 that the vehicle was designed for, without doing any engine modifications (compression ratio, porting, forced induction system, etc) then there is no benefit. None. Nada. You can put in any fuel you like, but it won't help. Some will argue that better fuels have more of the additives that keep the combustion system clean, but that was more true ten years ago than today. When Techron first came out at Chevron, the % varied by pump grade. That difference has largely disappeared. The entire marketing program called Top Tier is about eliminating that variable, which had largely disappeared in any case, if you are looking at name brand fuels.

For instance: on May 10 when my Dad and I head up to Thunderhill Raceway in Willows, CA, we're going to fill upon 100 octane at the track because my understanding is that our X's *CAN* calibrate for 100.

Not true. Your X5 can handle 100 pump octane fuel, but it can't calibrate for it, that is to say that it can't take any advantage of it. Go ahead and put it in if you like, because driver confidence is a big part of racing, and if you think you are faster, you may be. Just don't attribute it to the fuel.

[Riyad Aliyev]

thank you JCL for explanation. but still, nobody realy answered my question, is it ok if i'm going with this "Shell V-power 100" on my little beast named X5 4.8is?