Why do some cars need premium unleaded and others can use the cheapie regular unleaded?

Answer 1

good question.
To understand why some cars need premium, you need to know the difference between fuel types and engine types.
Unleaded fuel has more impurities, and this causes it to burn slower in the cyl. burning slower means that it also doesnt burn evenly. Premium fuel filters out those impurities, and burns faster.

A civic has a compression ratio (displacement+volume/volume) of 10:6:1, therfore a slower burning fuel will fully ignite in the space alloted.
A e46 bmw has a compression ratio of 16:8:1. So you have a much higher compression ratio, therefore you need a fuel that will ignite faster.
Now what happens when you stick premium in the civic, when its not required?--> nothing, as long as the fuel burns completely youre fine.
however, when you stick regular in the bmw, the fuel does not have enough time to burn, therfore, not all the fuel is burnt, and then you get what they call 'detonation'. Detonation is an uncontrolled explosion caused by latent fuel and heat in the cyl. This could cause vavle damage, or cyl damage..

And to those other posters who says it doesnt matter, IT DOES MATTER! its not that it burns cleaner, its that it burns faster.
if your car says to use premium, you MUST USE PREMIUM!

Answer 2

The octane of gas doesn't matter in most consumer level cars. Most cars can use cheap unleaded gas, and even the higher end luxury cars don't need the expensive stuff. The premium unleaded gas just burns cleaner so therefore it supposedly is better for your cars engine, less buildup of grime in the engine. Only high end sports/racing/(super high luxury) vehicles need the premium unleaded. So unless your racing in the indy 500, you don't really need the expensive stuff, unless u really want it.

Answer 3

I don't think any car absolutely needs premium unleaded. The gas just causes less knocking in the engine.

Answer 4

because some engines are built more to be performance engines,and they need more octane then a regular daily driver does,and the compression ratio any engine has decides what gas it will need to perform right ,although some engines they say needs higher octane,it has been proven that they will run good on a lower grade of fuel,good luck,i hope this help,s.

Answer 5

Higher compression in the engine needs higher octane gas - but gives more power. Also, the more advanced the ignition timing is, the higher octane gas you can use - although it won't get you much extra power (if at all.)

Answer 6

Depends on the compression and timing of the motor.