Premium or unleaded?

Question

I have just purchased a 1991 bmw 320i, it says to use premium unleaded 95, do I have to use premium or can I just use regular unleaded? I don't really care about the performance, but I don't want to blow engines or ruin anything!!!

Answer 1

you better use what the owners manual recommends or look for motor trouble down the road.

Answer 2

regular unleaded will be fine.  you will not see any difference if any amount of driving .  i have a v8 truck and i use regular unleaded.

Answer 3

If it recommends premium you can probably get away with regular. However if it states that it's required, do it or it'll dramatically reduce the life of the vehicle.

Answer 4

Use what the manufacturer recommends, The engine could be damaged from lower grade fuel. A knock from lower grade fuel cannot always be heard until the damage has been done.

Answer 5

yes, it will be cheaper now but in a couple of years that engine might start failing you. i recommend always listening to the manufacturer.

Answer 6

Eugene did a decent job of outlining how octane ratings work and their results.  

Main point is...engine pre-detonation, or pinging, is not good for the engine at all.  You can try the lower octane for sure, but if the pinging starts, do not use again.

Answer 7

what did the previous owner use?

unleaded should be fine but using premium will

help the lifespan of you engine!!

Answer 8

Look, here's the deal on octane ratings... the higher the octane, the less likely the fuel is to "pre-ignite" or "ping".  Newer cars have ping sensors (or the like) to r****d the ignition timing to reduce ping, if detected.  Once it reached the limit of timing, now all you can rely on is the fuel.  So, if you put regular in the car, and you hear it ping, you'll need to put higher octane fuel in to reduce the ping OR add octane booster to your fuel, which may be cheaper.  

If your car pings, it will take its toll on the engine over time.  The fuel is "exploding" in the cylender versus burning nicely, and it does so at the wrong time.  

So, you can run on as low of octane as possible until you get pinging (usually under heavy throttle at low RPM).  Octane has VERY little to do with the power derived from the FUEL, but your vehicle's ability to run at advanced timing to better burn it, thus creating more power.  There is precious little difference in the energy content of a gallon of regular versus a gallon of premium.  

Okay, so here come all the criticisms on racing fuel and 100LL aviation fuel, but for the most part, the higher octane just lets you advance the timing more.  In specialty fuels, you do get some increased energy potential in the reduction of impurities too.

Anyway, put gas in that won't make the car ping, and you should be okay.  If it pings, move up to the next higher grade.