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Discussion Starter · #1 ·
As world oil price spikes due to middle east turmoil recently and the current nuclear crisis in Japan, i am getting more and more tempted to buy and put the government subsidized, low octane fuel into the car.

the choices available here are :

1. RON 88 > equivalent roughly to US AKI 86, around USD 1.50 per gallon (government subsidized)

2. RON 92 > equivalent roughly to US AKI 90, around USD 3.50 per gallon, i am currently using this.

3. RON 95 > equivalent roughly to US AKI 93, around USD 3.90 per gallon, i used before the price increased.

Could anyone advise on the short term and long term effect on using the low octane fuel on our E39 ?

Will it cause a long term damage to the internal part, other than less power due to the ECU has to re-time the engine to overcome the knocking because of the uncontrolled detonation ?

I would like to know your clearly advance knowledge over this issue. I plan to keep the car for long term, i am just getting overwhelmed by the current oil price, i could spend around USD 50 per fill up. Its just torturing.

Any input will be highly appreciated.

Thanks and regards from Jakarta.
 

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Check your owner's manual for the minimum octane requirement. The ECU can only adjust the timing so far, and that is why the minimum octane is specified. You could try a tankful of the cheap stuff, and see how the car runs. You may be disappointed.

We have pump octane here of 87, 89, and 91. The price spread is only 0.10 grade-to-grade, so I use 91 (0.20 more expensive per gallon than 87). My gas cap specifies 89 minimum.

BTW, have you changed your VANOS seals? Worthwhile job.
 

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Completely off the wall question here .... Wouldn't using waterless coolant (NPG+) alleviate the symptoms (pre-detonation, knocking) commonly associated with low-octane gas?
 

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Discussion Starter · #5 ·
Check your owner's manual for the minimum octane requirement. The ECU can only adjust the timing so far, and that is why the minimum octane is specified. You could try a tankful of the cheap stuff, and see how the car runs. You may be disappointed.

We have pump octane here of 87, 89, and 91. The price spread is only 0.10 grade-to-grade, so I use 91 (0.20 more expensive per gallon than 87). My gas cap specifies 89 minimum.

BTW, have you changed your VANOS seals? Worthwhile job.
Hi Ed,

Actually i did once and yes, i disappointed, it was very sluggish, i would revise the conversion, the RON 88 here is equivalent to AKI 84 in the US. However, i am really curious on the side effect of the low octane gas other than an inferior performance of the car.

I have not done the VANOS as you did, do you think its needed for it with only 25000 miles ?
 

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Discussion Starter · #6 ·
Completely off the wall question here .... Wouldn't using waterless coolant (NPG+) alleviate the symptoms (pre-detonation, knocking) commonly associated with low-octane gas?
Sorry, i don't get it. Please explain "waterless coolant" ?
 

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84 or 86? You said 86 in your first post.

You have the option of mixing 2 grades to save some money. Put half a tank of your $1.50 and half a tank of the $3.50 and you end up with a $2.50 per gallon gas.

Just check your manual (or look inside your fuel cap?) for the minimum octane requirement, and do your calculation as to what proportion of the higher and subsidized fuel that you will need to mix.

mw
 

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Discussion Starter · #10 ·
84 or 86? You said 86 in your first post.

You have the option of mixing 2 grades to save some money. Put half a tank of your $1.50 and half a tank of the $3.50 and you end up with a $2.50 per gallon gas.

Just check your manual (or look inside your fuel cap?) for the minimum octane requirement, and do your calculation as to what proportion of the higher and subsidized fuel that you will need to mix.

mw
Thanks, the manual says min RON 91. However, if most of you would direct that no long-term damage would be done to the engine / system by the use of lower than recommended octane fuel, i would really really be willing to accept a less performance for some times until the oil price get back to normal.

After i calculate again, i think the conversion from RON 88 is more to AKI 84.
 

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That's because there's no connection.
 

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Sorry but i read the whole 9 pages and cannot find any relation between this coolant and the low octane fuel :dunno:
That's a thread on using waterless coolant in an e39 540i. You didn't know about it so I linked to that. Google a bit if interested, and you'll find lots of threads on the web about Evans NPG products reducing hot spots in high-performance engines and allowing the use of lower-octane fuels.
 

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Years ago, the company I worked for had an agreement to fuel their trucks at specific gas station and the drivers would just sign, and we'd pay the bill by the end of each week. One of my perks was that I could fuel my 528 there for free (the company would pay).

As usual, I only used the highest octane (93).

But I noticed that the car was noisier when I accelerated or when going toward the 3000 rpm. It went on for like a year, and since the car was new to me, I didn't know if that was something, but I definitely noticed.

Then a few times when I was away from around the office, I fueled at regular brand name stations, and the noise was not there, and the engine was smoother to rev up. One more time at the 'bad' gas station and the noise came back and I knew something was wrong with their gas. I convinced my bosses to reimburse me for fuel at the gas station of my choice, and that was the end of it.

A few months later I passed by that gas station and it is closed, the ground was dug out. I asked around, and they said that he is "renovating" and fixing his underground gas tanks.

Guess what? That station owner was an owner of a few gas stations, AND an owner of Gas Tanker Trucks. (That's how he started - supplying gas to stations). My suspicion is that he simply put the low octane gas in the "Premium" tanks and made money cheating people. He got caught at an inspection, and when confronted, played dumb and said "maybe there's a leak underground". I don't know. Maybe he was fined and had to dig out the older tanks.

Was that noise a detonation noise? I am not sure. Maybe / probably.

My engine is still fine. Is there any internal extended wear and tear? I don't know.

Would I do it again for free gas? Hell NO.

Detonation is bad, right? We all know that.

I look at it this way: If I jump of a 10 floor building, I know I'll kill myself.
If I jump of the second floor, (10'), I'll be ok.
If I jump of the third floor, (20'), I don't know. It wouldn't kill me. Will I hurt myself? If I jump 10 times, probably yes.

Here the thing. I would not try to analyze what damage would happen to me if I jump from the 20' high. I don't care. I simply will not jump.

Now if you'd pay me a million dollars, I would. But I wouldn't for $50. :rofl:

mw
 

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Completely off the wall question here .... Wouldn't using waterless coolant (NPG+) alleviate the symptoms (pre-detonation, knocking) commonly associated with low-octane gas?
No connection, so no. Low octane gas explodes earlier so the timing needs to be adapted. Lower boiling temp of the coolant simply means that there is lower pressure in the cooling system. Some tests have shown that NPG has poorer heat transfer characteristics so the engine is actually hotter, which would increase detonation.
 

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No connection, so no. Low octane gas explodes earlier so the timing needs to be adapted. Lower boiling temp of the coolant simply means that there is lower pressure in the cooling system. Some tests have shown that NPG has poorer heat transfer characteristics so the engine is actually hotter, which would increase detonation.
I won't waste the OP's time with this any further as I haven't tried it myself, just that with the interwebs being what they are, you'll find posts to support any viewpoint. The reason I brought it up was that I had been reading that NPG+ (higher boiling point by the way, not lower, that's why the system has less pressure...) alleviates cavitation in the coolant passages around cylinders, thus getting rid of hot spots, a cause of pre-ignition or knocking, and -theoretically- allowing one to take advantage of lower-octane fuels. I will type no more on the subject. Carry on.
 

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1. RON 88 > equivalent roughly to US AKI 86, around USD 1.50 per gallon (government subsidized)

2. RON 92 > equivalent roughly to US AKI 90, around USD 3.50 per gallon, i am currently using this.
Geez! $1.50? I'm paying over $4, so I'd even welcome $3.50 for 92.:bawling:
 

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Check your owner's manual for the minimum octane requirement. The ECU can only adjust the timing so far, and that is why the minimum octane is specified. You could try a tankful of the cheap stuff, and see how the car runs. You may be disappointed.

We have pump octane here of 87, 89, and 91. The price spread is only 0.10 grade-to-grade, so I use 91 (0.20 more expensive per gallon than 87). My gas cap specifies 89 minimum.

BTW, have you changed your VANOS seals? Worthwhile job.
Hi,

91 is .15 cents more per liter than 87 here in Canada -- I think that works out to about .57 cents more per gallon .. what can we do ?

George Allan
 

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Hi,

91 is .15 cents more per liter than 87 here in Canada -- I think that works out to about .57 cents more per gallon .. what can we do ?

George Allan
A: You could move to Jakarta.

mw
 

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i need to know the real damage it is doing to the internal parts of the car.
Don't do anything you're uncomfortable with ... but ummm... if it's not pinging, there's (whether or not that's because the knock sensors are retarding the timing), there's no damage.

In fact, optimal engine efficiency is at the point of pinging (just before), so, you really wanna get as close as you can sans actual pinging (which would be a bad thing).

Anyway, no need to argue ... you do what you do ... I do what I do ... and neither one of us is ruining our engines.

I didn't open this thread ... I simply responded to it. I understand octane and gasoline and pinging rather well ... as do you. Given our knowledge, we each make our own decisions and live with the consequences.

Good luck.
 
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