170 Degree Thermostat fits various closed cooled Crusader V8 marine engines. Thermostat fits various closed cooled Crusader V8 marine engines. 170 degree temperature for closed cooled engines Fits: Crusader TB350XL/TB350HT fresh water cooled marine engines from serial number 90232 & up Carbureted Crusader 5.7 Classic Series fresh water cooled marine engines from 1999 to 2005 Captains Choice MP5.0/5.7 fresh water cooled marine engines from 2004 to 2005 TB454XL fresh water cooled marine engines from serial number 92882 & up MP7.4 and MP454XLI fresh water cooled marine engines Replaces Crusader 98203 | Replaces Crusader R026007A | Replaces Pleasurecraft R026007A | Replaces Marine Power 0500-007 and 515411 Original Crusader Frequently Asked Questions Is there an octane grade that is advised for Crusader engines given the current rise in gas prices? Maximum performance is attained while using 87 octane fuel since Crusader fuel injected engines are tuned to run on it. For usage with the factory-set ignition timing, premium regular gasoline with a (R+M/2) octane rating is required. Does crusader recommend a specific type of oil for their engines? Use a high-quality SAE 15W-40 "SJ" when the average temperature is over 50 degrees Fahrenheit. Use SAE 5W-30 "SJ" below 50. It is not advised to use synthetic oils in Crusader engines. Explain Crusader's position on ethanol use? This warning only applies to CRUSADER engines and their usage of ethanol fuels. The usage of ethanol fuels in vessel-related parts such as boat gas tanks, boat fuel lines, boat fuel filters, etc. is not addressed. The boat owner is STRONGLY ADVISED to speak with the boat manufacturer about whether using ethanol fuel in their boat is appropriate. Ethanol-blend fuel with an E10 or below rating is permissible. Fuels with ratings greater than E10 is NOT advised. Higher than E10 ethanol fuels have the potential to harm the engine and/or create hazardous boating conditions. The guarantee does not apply to harm to the engine brought on by the use of ethanol gasoline with an E10 rating or above. What kind of coolant is recommended to be used in a Crusader engine / cooling system? For engines with closed cooling systems, Crusader suggests mixing 50% DEX-COOL to 50% water, or any other suitable extended life coolant (pink/orange in hue). Overheating may result from coolant levels greater than 50%. Do not combine DEX-COOL with conventional silicated coolant or use it in its place (green in color).