Is Octane 94 an overkill

Average Jae

Average Jae

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#21
while you wouldn't want to spend anymore money on gas that you'd need to; why would you take a chance on reduced performance? that's like paying thousands and pinching pennies. Oh wait, it is paying thousands more and counting pennies.

but then again, there are some that roll nice rides like bimmers, lex, mercs etc and have car payments higher than their appt payments.
 
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Big Daddy

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#22
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#22
10:1 is a higher compression ratio than 8:1.

My 91 318is, M42 motor required 91 octane as does my 91 750iL and my 98 M roadster.

Premium fuels also contain injector cleaners and other additives that may not be in the lower grade fuels. So other than octane there may be some other benefits, and at 10-20 cents per gallon, maybe up to $4.00 difference per fill-up, I would err on the side of caution.
 
jrt67ss350

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Epi330 said:
It is very unlikely that compression ratio can increase over time. Quite the opposite - when parts wear and loosen, the compression is not that great anymore, so you can use lower grade than when car was new.
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Compression can increase over time if there is carbon buildup in the cylinders or on the valves. If the injectors are cruddy and not flowing like they should, then the engine can start running lean and require higher octane fuel to prevent pinging as well.

An 8.8:1 325i should not require anything higher than 87 octane gas (especially since they have aluminum heads, which effectively reduce the required octane level) unless there is carbon buildup in the engine.
 
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h317

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#24
Average Jae said:
while you wouldn't want to spend anymore money on gas that you'd need to; why would you take a chance on reduced performance? that's like paying thousands and pinching pennies. Oh wait, it is paying thousands more and counting pennies.
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Is there any added benefits using 94 on an unmodified 330xi (I value snow driving capability over performance when making the purchae decision). I may be wrong but I doubt that one can tell the difference between two identical cars using different octance grade (94 vs 92).
 
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panzershreck

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#25
jrt67ss350 said:
Compression can increase over time if there is carbon buildup in the cylinders or on the valves. If the injectors are cruddy and not flowing like they should, then the engine can start running lean and require higher octane fuel to prevent pinging as well.

An 8.8:1 325i should not require anything higher than 87 octane gas (especially since they have aluminum heads, which effectively reduce the required octane level) unless there is carbon buildup in the engine.
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thats the M20 engine right? [???1] My engine seems to have just enough carbon buildup that 89 or 91 is the preferred octane
 
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bimmerman

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#27
using a higher octane than required by the manual only helps by burning more cleanly. To say there aren't any advantages isn't true... over the very long-run, putting premium vs. regular in your car can make a difference even if you don't consider knocking. I have seen one or two gas stations that sell 92 for the same price the one down the street sells 93. So I buy the 93, same price for better gas.
 
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Epi330

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#28
bimmerman said:
using a higher octane than required by the manual only helps by burning more cleanly. To say there aren't any advantages isn't true... over the very long-run, putting premium vs. regular in your car can make a difference even if you don't consider knocking. I have seen one or two gas stations that sell 92 for the same price the one down the street sells 93. So I buy the 93, same price for better gas.
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No, you didn't get the point. Higher octane number does NOT mean "better gas". 93 does NOT burn "more cleanly" than 92 with everything else being equal.

There may be difference indeed for different brands of gas, like some manufacturer adding different additivice to "premium" gas than "regular" one, as Big Daddy said (although I cannot confirm it, and from what I heard it's not true for Chevron). However, 93 from one gas station is not neccesary better than 91 from another. Given their same price, it may be even worse - 91 with additives is usually better for your car than 93 without additives.
 
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bimmerman

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#29
do you have any idea what you're talking about, or are you just shooting from the hip? Higher octance fuel is lighter, and burns more easily, hence more cleanly. Diesel, a heavier fuel, doesn't burn as well, and leaves more residue. 93 to 94 octance is much less of a difference, but it still has the same effect.... and 93 at one station is "supposed" to be as light as 93 at another station. And for the record, I would take the one without additives. Write back after you do some research.
 
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panzershreck

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#30
bimmerman said:
do you have any idea what you're talking about, or are you just shooting from the hip? Higher octance fuel is lighter, and burns more easily, hence more cleanly. Diesel, a heavier fuel, doesn't burn as well, and leaves more residue. 93 to 94 octance is much less of a difference, but it still has the same effect.... and 93 at one station is "supposed" to be as light as 93 at another station. And for the record, I would take the one without additives. Write back after you do some research.
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after all the research ive already been doing... higher octane does not equal more easily burnable, in fact, its the complete opposite... as octane is a resistant against combustion, it becomes necessary in higher compression engines which would otherwise knock (detonate before the spark plug activates)... similarly, an engine with low compression and too high octane fuel can detonate too late or not at all (which sets up for pre-ignition detonation which can be much worse than knocking)... in other cases, an engine with low compression ratio using high octane gas will lose performance due to the resistance of the fuel to combust and carbon deposits will be accelerated in this case, again reducing performance of an engine... additives are sometimes the only reason people even purchase higher octane gasoline, however all gasoline grades now have additives in them (correct me if im wrong)

there is no difference between which fuel itself runs more smoothly as it is with which engine runs more smoothly with different types of fuel
 
carcus

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#31
Well, this is my personal preferance, I run 93 in my 328. I have a choice at the pumps out here of 89, 89, or 93. I go with the 93 most of the time unless I have long distance highway driving. My car just runs better with the 93, I would use 91 if they sold it but the lower octane will not damage your engine. I think with your 04 BMW, you would want the good stuff. Personally, anything over 91 would really not be that much of a difference....again, I only use 93 because 91 is not sold around here....and at $1.85 a gallon for 93, it is not killing me. If you get your car sharked, you will have to use the super to take advantage of the programming. Rule of thumb, if your car does not knock, you should be fine with lower octane. On another note, using some of the very high 101 stuff and the expensive race octane gas is kinda pointless for street driven cars. Alot of this really comes down to what mods have been done to the car and compression ratio of the engine. Correct me if I am wrong, but I would think the owners manual for the 330 would require premium fuel? IMHO......pass on the 94, the 91 should be perfect for you.
 
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rjp325i

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#32
There have been many opinions here but not too many facts. Higher octane gas burns more slowly than lower octane gas hence its resistance to knocking. The slower burner higher octane gas when used in an engine that does not require it may cause an excessive amount of carbon build up which then necessitates using the higher octane gas to obtain full power. In essence you make your car into a premium fuel junkie. Some fuel retailers insert more additives into there premium fuel while others do not. You can contact the gas suppliers to find out if your favorite brand does so or not. Chevron, the last time I checked is one that uses the same additive pkg in all its gasolines. I'm sure there are others as well. Cleanliness inside an engine combustion chamber is a necessity to keeping an engine running like its supposed to as well as deliver good mpg. The M20 and earlier family of engines do not have knock sensors. The M54 family of engines do have knock sensors which cut back on the engine timing to eliminate knocking that can occur when a lower grade gas is used. Cutting back on spark advance also reduces power. Is that what one buys a BMW for? When I had my '89 325i I used 87 octane without any problems. When I installed a Conforti/TMS chip a minimum of 91 octane is recommended and it would knock on anything approaching full throttle if less was used. However even the 91 is not adequate when ambient temperatures run quite high as they do in the desert southwest summers. The octane requirements of an engine increases as ambient temp increases. If anyone is familar with Metric Mechanic's Jim Rowe, he wrote articles on this. One appears in the book BMW Enthusiasts Companion published by Bentley. During the summer months I would mix a 25% mix of unleaded 100 octane to raise the 91 octane gas that we get on the west coast up to a little over 93 octane. I wish we had the Sunoco 94 here as is available in NY where I moved from 5 yrs ago. I have not had to do so yet with my 2004 w/ZHP but it is recommended by the local dealer for summer driving if full performance potential is to be realized as well as produce improved gas mileage. Sorry for the long post.
 
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rjp325i

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#34
Just a lot longer version of what was already posted and everyone knows each person is going to believe and do whatever they want to do. Follow factory recommendation and one will be safe. Trying to save 2 bucks on a tankful of gas when one spends 30, 40, 50 grand and more on a car is senseless. One thing that is mentioned that is valuable is not to mix leaded and unleaded gas in a modern engine. Although I do not know if you can readily get the leaded stuff any more. NASCAR has 110 octane pumps at the Speedway but that is limited to the race cars. We have unleaded 100 octane available at Union 76 stations. It is expensive at $3.959 /gal but it works well when mixed with the 91 crap that is the premium on the west coast (CA, NV etc).
 
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Epi330

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#35
bimmerman said:
do you have any idea what you're talking about, or are you just shooting from the hip? ... Write back after you do some research.
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And what about you? Doesn't it make sense to learn something by yourself before flaming others? Just follow the link Big Daddy posted
 
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newguy

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#38
94 Octane

When octane value is determined, it is analysed two ways. There is a "research" number that is determined by one test, amd a "motor" number that is a separate test. The two numbers are then added together, then divided by two. This gives the final number, which is what we see at the pumps as :road octane. The higher the octane, the smaller the tendency is for "detonation" to occur within the engine. It would seem that this would allow more spark "advance" to be used under "stress" shall we say, and I believe this would give an increase in performance. If your machine has been "chipped" it should allow more of its potential to be used. We produce 94 octane at my place of business...if the octane number is less than 94.0, say 93.8, we must reblend the batch..We have been known to let some with a higher number, say 94.3 get shipped
 
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bimmerman11

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#39
Big Daddy said:
I had a 79 Chev Pickup with a built 350, I mean built. It had 11:1 compression ratio and loped at an idle. I went through three transmissions before Summit Racing finally built one I could not destroy with the torque. This beast used 94+ octane.
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I hope you were using an octane booster every time you filled up, the highest compression you can run on pump gas is probably 10.5 to 1 and thats with 94. Theres no way in hell an 11 to 1 compression engine can run smoothly on pump gas. One of my friends has an old GTA with 350 tuned port and he upped the compression to 10.5 to 1 and ran like shit on 94 pump gas. So he's been using a methanol mix in his tank ever since.
 
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