No, not sarcastic. Genuine concern - I am a worrier - it is a big investment.Also not sure if this is sarcastic. If it is not, STOP WORRYING, go drive your Jeep. Fill it up whenever your heart desires. You will do NOTHING to harm your vehicle. Worse case scenario in about 40K miles you might get some knocking from using 87 octane. Again nothing will harm the engine.