2004 250XS Fuel octane

[Viper 25]

Hi, Can anyone tell me what will happen if i use 87 or 89 octane fuel in my 2004 250XS? The recommended fuel is a minimum of 91 octane!!!!

[dnelson964]

Your motor is running with "high" compression compared with "low" compression in the cylinders. You need high octane (91 or better) so the fuel has a more controlled combustion property or it will pre-ignite. Pre-ignition can plan just ruin your motor. Without me explaining any further technically and for a few cents more at the pump.....just use 91 or higher!!! Never lower!! Higher compression is giving you more HP but the trade off is you need higher octane gas to run it.

[Viper 25]

Many thanks for your info but i'am having a problem getting high octane fuel over here!!! Would it be reasonable if i had to mix racing fuel with normal unleaded fuel to boost the octane rating???
Would i loose Hp if i use normal unleaded and if so how much?
What about Lucas Oil Octane booster ???

[dnelson964]

Then octane booster would be good or mixing with racing fuel would also be another way to increase your octane yes.

[aaronmt73]

You may be better off selling the motor if 91 and above is that hard to get.It wont last long if you try to run lower octane fuel.You could easily see that motor and buy a standard Optimax that would fit your needs better.

[ar300johnson]

Add 100 octane avgas. I part avgas 1 part 87. Plenty of octane, no detonation.