What happens if my car is filled up with regular gas?

[Kennection]

Ok so I remember hearing about how the 318ti's don't use regular gas, and use the 92(I believe it's this one?). So yea, my very first car as a 17 year old, so I'm not all knowledgeable with my car yet (Parents bought it from a friend for me). Anyways, my grandfather has a spare key to my car, and when he notices that I'm almost out of gas, he'll go out and fill it for me. I just found out that the past two times he's been filling up the car, he's been filling it up with regular gas.

My question is, should I be noticing something about my car when it's been filled up with regular gas?

I was driving it around today, to do some errands and I started noticing how my car was making some really odd noises. I would step on the accelerator and would notice some noises coming from the engine for about a few seconds, then it'd go back to regular. Also would notice that when I let go of the accelerator and was about to tap the brakes.

Not sure if I should really be worried or anything, or that I should just wait for my gas to run out after awhile and fill it up with the premium gas.

Thanks.

[pdxmotorhead]

It won't really hurt anything. The engine will just lack power, and may ping, drive gently.
If the outside air temp is below 45 or so I run 87 or 89 because it raises temps and evaporates a little easier than premium. If the noise sounded like some rocks in a tin can shaking around that's pinging. You can always top the car off with premium and add a correct dose of name brand gas treatment. Like Techron. It will bump the octane a point or so.

Dave

[Kennection]

It's more of a loud humming noise than it is rocks... Thought it might have been the regular gas.

[pdxmotorhead]

The AC system on these makes a weird growl it was a recall item way back. My AC also makes a humming noise when running normally.

Possible alternator or water pump as well.

Dave

[tiFreak]

it can cause some problems with carbon build-up if you use regular for a while, with just two tanks of gas it won't have caused any harm, 89 octane is what it calls for

[bmvw]

I didn't know it was supposed to get 89. I've been running 87 for three years now.

[graymae]

Originally Posted by bmvw

I didn't know it was supposed to get 89. I've been running 87 for three years now.

i knew it was 89, but money is tight so i use 87.

[pdxmotorhead]

Mine gets enough better mileage running the 92 that I run it all the time, takes about 2 tanks to get the computer calibrated.... 34 vs about 28 on 87 and 30 on 89

Dave

[projekt EPiK]

i'll have to experiment with this.. been running 87 since i got the car since it is my DD and i dont put the engine under heavy load.. the reason for increased octane is detonation resistance slowing fuel burn. more octane = slower burn.. the reason my high octane fuels are required for high performance..esp. turbo/sc cars.

i'm getting 25-26mpg around town now on the 87 and 34 hwy, i'll try a tank or 3 of 89 and see what happens. FWIW.. i've had no ping on the 87 even on the odd occasion that i rev it all the way out thru 1st, 2nd and 3rd.. merging or something.

[XMcBainX]

The owner's manual says that the car takes any kind of fuel. The fuel sensors will compensate for fuel type used. That being said, the car is designed for use with higher octane levels (89), lower octane gas should pose no problems.

[jordanmc]

This is right out of the owners manual:
The higher-octane fuels will provide increased performance and fuel economy, while the use of gasoline with a lower octane rating will have an inverse effect.

[bmvw]

So here in CA premium is $0.20 more per gallon than 87. At $3.00 per gallon, if fuel economy increases more than 6.7% by using premium it will be worth it. Has anybody tried this yet??

[MPWR]

Originally Posted by projekt EPiK

the reason for increased octane is detonation resistance slowing fuel burn.

Exactly right- and it is actually a very serious issue.

"Knocking" and "pinging" are actually detonation and pre-ignition. These are very damaging phenomenon that happen in internal combustion engines that are pushed too hard and/or run on the wrong fuel. They are actually violent miscombustion- when fuel explodes in the cylinder instead of burns smoothly. If allowed to happen, this can quickly destroy an engine.

BMWs (like most cars in this era) are electronically protected from detonation. Small microphones (knock sensors) on the engine block listen for the sound of detonation occurring, and when it does the engine performance is electronically reduced until the issue stops. But of course if knock protection is activated, it means that it is already happening in your engine- and it is an unhealthy thing, especially if you want that engine to last for a while. The driver will never hear an OBD2 engine knock or ping- the ECU will eliminate it long before the driver becomes aware of it. But that doesn't mean it is not happening, if only momentarily.

In short, you certainly can damage your engine by using a lower grade. If you only occasionally use the wrong stuff (filled by mistake, they were out of the right stuff), it's not a big issue- the engine will do it's best to protect itself. But you really should not use cheap gas in a ti regularly- especially if you're only trying to save a couple of dollars. Engine damage is expensive....

[MacUser]

Originally Posted by MPWR

Exactly right- and it is actually a very serious issue.
... Engine damage is expensive....

While I'm no expert, I've read a good bit on the subject ... I couldn't have said it better myself.

A few weeks ago, I was driving through rural Ohio at night and came across a gas station that only had 87. Each pump had three nozzles, but every single nozzle was labeled "regular" and "87". I was not pleased. I always choose the highest octane rating available (well, not Sunoco Racing Fuels). My understand is some pre-detonation is audible, other pre-detonation is not, so I don't rely on the noises I hear.

[budget76]

I always run plus or premium, depending on the price gap between the two & the amount I'm buying. If I'm going to get an extra gallon running plus, I'll use plus, if not premium.

I personally am getting >20mpg around town/city driving, and get 25+ at 75-80 on the highway with my M50. I got 35mpg with the 6cyl the one time I did 55mph

IIRC when my friend put regular into his TI, the CEL came on and stayed until he burned half the tank and filled it with premium.