Originally posted by HITMANinMI:
Originally posted by Kremithefrog:
Originally posted by HITMANinMI:
Originally posted by NOBLE818:
Ohh man! I've been wasting my money using higher octane (91) cause i was thinking it was better for the engine. But after reading this post I come to find out I was just wasting my money and it is better if I just use what is recommended, which is (87) rated gasoline. Well from now on I guess i'll be saving money on gas!



Yeah well dont add 87 to a tank that has 91 in it, get the tank as empty as possible before switching octane ratings.




And the logic behind that would be....? You can mix any octane level you want without problems, than again, contour atx's don't have drain plugs, right, so what do I know?



engine knocks like hell if you do



Now, where did your hear a thing like that? Mix 91 and 95 octane and you get something like 93 octane. The engine will knock only when the octane is way bellow the recommended level, or if the compression ratio is way up for the same octane level. Modern engines, with EEC'S running the show can retard/advance ignition point in order to meet the fuel octane rating. Up to a point though. Knocking is a spontaneus combustion of mixture that happens before the TBC ( It hink that's right acronim, if not it's the "Upper dead point in our language here) and can result in serious damage to the valves. It occurs when the octane rating is lower that recommneded, or the compression is higer than it should be. So using higher octane fuel will not hurt the engine, nor will mixing it with lower octane fuel, providing it does not go bellow the recommended level.

airman1 Black '95 Mondeo V6Si