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I got a full tank today for my 2004 BMW 325xi which requires
premium unleaded according to the manufacturer.

I specifically asked for "super".
When the elderly gentleman gave me my receipt (and walked away), I noticed the price was that of regular, instead of the super price posted at the pump. I also noticed that the receipt stated "unleaded" (i.e. 87 octane), rather than "premium" (93 octane, recommended by mfr) or "plus" (91? octane).
COULD THIS CAUSE DAMAGE to the car's engine or components?Stupidly, I drove away, not thinking about the potential problems.
This was on a highway where the u-turns are 20 minutes apart.
Therefore a few minutes later, when I decided it probably wasn't good for the car, I couldn't go back.

I decided to go to the next gas station (17 miles away) and try to get it syphoned.
Unfortunately in NY state they are all self service, unlike NJ.
Anyway, I drove for almost an hour (several stops at gas stations and traffic jams in the town my gf and I went to due to a parade) to try to find a garage to syphon it. Midas was closed.
In the end, I went back on the NYS Thruway and went the opposite direction. The nearest gas station was about 5 miles away.
I asked about syphoning it, but there was no accompanying garage, so the kids working there couldn't do it.
The kid suggested "104 octane booster" (some race car driver's name is part of the product name, but I forgot what it is called). He added a bottle to my still nearly full tank of gas.

My questions are as follows:

1) Is it bad to drive the car with ONE tank of gas of regular gas in MY particular car which requires 93 octane fuel.

2) Could did the octane booster fluid (used for ONE tank of gas) actually
cause more harm than good? I read somewhere that it can affect the car's engine computer, by making it adjust settings etc.

3) Should I bother to TRY to get it syphoned?

4) Should I top it off with premium fuel now that 1/4 of the fuel (including octane booster fluid that took up some space in the tank) has been used?
Or should I wait since the octane booster was used and may have already boosted the octane level closer to premium?
I read somewhere that it doesn't really boost the octane that much unless it is used in higher quantities (not sure about the validity of that statement).

Thanks for any tips!

Happy Memorial Day!

One tank of standard grade probably won't give you issues.

My 1994 Acura Integra GS-R requries minimum 91 octane premium. If I were to use standard grade gas, the sensors in the engine would detect it, and moderate the valve timing, reducing performance but allowing the use of standard grade fuel. In high compression ratio engines (I believe mine is 10:1 or so), high octane is needed for the engine to perform at its best and to avoid spark knock. Fortunately, in Michigan we are allowed to pump our own gas (my understanding is that you are not). Best bet next time is to complain immediately to the gas station where you were fueled at.

Adding octane through a can of booster is certainly an option in this case, but just one tank of gas shouldn't cause long term damage to your car.

Yeah most modern cars have knock sensors so I wouldn't worry about it...but you might not want to over-rev the engine until you get some high octane in the tank.

Your car is probably ruined. You might as well give it to me now.

Seriously, I wouldn't worry about it. It's a BMW. It could probably run on German beer if need be.

Thanks for the reassurance guys!
Not being a mechanic, and not being familiar with new engines and octane levels, I wasn't sure...

Ian wrote:Your car is probably ruined. You might as well give it to me now.

It'll be in your driveway tomorrow morning.....not

The car is just not going to run optimum during that tank.

BTW, most people actually don't read their manual and put in too high of an octane. This can apparently damage the engine as it is exceeding the force the engine was designed for. I thought that was amusing. I'm amused.

No it won't damage your car. I belong to the BMW club (X5 owner) and it is not uncommon for us to use non-premium gas once in a awhile like in cases of emergencies or long trips as one gets better mileage on regular unleaded than the premium one. You may notice a slight decrease in power but it won't hurt it.

That may be another urban myth. Higher octane gas may be wasteful, but it shouldn't do any more damage than regular gas. Under high temperature and pressure, gasoline vapors will spontaneously combust without the aid of a spark. This "detonation" is the "knocking" most people talk about and what the knock sensors listen for. High octane gas is needed to prevent detonation in high performance engines due to the compression ratios used. In normal engines, it should have little adverse effect, if any.

KuoH

JamieW wrote:BTW, most people actually don't read their manual and put in too high of an octane. This can apparently damage the engine as it is exceeding the force the engine was designed for. I thought that was amusing.

JamieW wrote:The car is just not going to run optimum during that tank.

BTW, most people actually don't read their manual and put in too high of an octane. This can apparently damage the engine as it is exceeding the force the engine was designed for. I thought that was amusing. I'm amused.

That's not true at all Jamie!!! You are just wasting money by using higher octane rated gas. No damages to your engine. You will NOT get any more force or power by using the higher octane. I hope this is what you were amused about rather than just the fact that people don't read their manual.

Thanks for all the helpful feedback.
I am glad I learned a bit more about octane and its effect.

I will not over rev the engine till I get a fresh tank of premium.
In the meantime, I will probably top it off with premium once it gets to about half full, to boost the octane level, unless the octane booster can's fluid really did it boost it be several points - I haven't researched octane boosters.

Ironically, if I remember correctly, someone on another forum said octane booster may actually not be good for the car, although I am sure that is more of an issue if it is used on a regular basis, as opposed to using it once in an emergency, if that poster's claim is true in the first place.

Run anything less than 93 octane in me and brothers Trans Am will blow the head gasket at best. Very high compression race engine but in a stock car I wouldnt worry too much. My Corvettes required premium fuel too and I tried running 87 octane in them before and they knocked and soounded bad. 1 time experience.

No, I was amused thinking that high octane can cause more harm than good. Didn't know it was an urban myth. Thanks. Now I go yell at Darrel.

Well actually, using a high-octane fuel in a low-compression engine can cause damage over time; unburnt fuel may escape through the exhaust system and damage the catalytic converter. So no damage to the engine itself, but a potential $300 bill down the line come emissions test day.

I guess one time with normal fuel wont damage it.And as Ian said,it's a BMW.


::Pranav::

Ah BMW. Well then yes, of course it'll do no damage.

Great British Rover on the other hand, blown head gasket, probably a snapped cam-belt, oil all over the engine bay, pistons all bent, probably knocking itself off its mountings and twisting the chassis. All within 30 yards of leaving the forecourt......

jase wrote:Ah BMW. Well then yes, of course it'll do no damage.

Great British Rover on the other hand, blown head gasket, probably a snapped cam-belt, oil all over the engine bay, pistons all bent, probably knocking itself off its mountings and twisting the chassis. All within 30 yards of leaving the forecourt......

Well,I really dont think it will do damage in a short round,not except you use kerosene instead of petrol.


::Pranav::

one tank of gas like that won't hurt it, it will hurt your Performance though. If I put cheap crap in my 1998 Z28 I can tell a huge difference.

Just go to a Autoparts Store and get some Octane Booster that will fix you up.

not to go into a very long winded post but octane booster in a bottle is worthless to octane ratings.They work by cleaning the combustion chamber therefore removing carbon buildup which holds hot spots which may help lower chance of detonation. To truly raise the octane of fuel one must add lacquer thinner (Toluene) at a rate of 8 to 10 ounces per gallon of 93 octane gas to get right at 100 octane. You can buy generic laquer thinner at Auto Zone for about 4 bucks a gallon.This is how most people do it at the track with us as race fuel contains lead and is around $5-6 a gallon for 104 octane.As you can see once again another snake oil product out there. There is no way a 12 oz bottle of octane boost will raise your cars entire tank of fuel even 1 point yet alone 104+ as claimed by some.