2002 Nissan Xterra Owner's Manual - Page 230

If any driveability problems such as engine stalling and hard hot starting are experienced after using oxygenate-blend fuels, immediately change to a non-oxygenate fuel or a fuel with a low blend of MTBE. Take care not to spill gasoline during refueling. Gasoline containing oxygenates can cause paint damage. southern Idaho, western South Dakota, western Nebraska, and the part of Texas which is directly south of New Mexico. Using unleaded gasoline with an octane rating lower than stated above can cause persistent, heavy ''spark knock Spark knock'' is a metallic rapping noise.) If severe, this can lead to engine damage. If you detect a persistent heavy spark knock even when using gasoline of the stated octane rating, or if you hear steady spark knock while holding a steady speed on level roads, have an authorized NISSAN dealer correct the condition. Failure to correct the condition is misuse of the vehicle, for which NISSAN is not responsible. Incorrect ignition timing may result in spark knock, after-run and/or overheating, which may cause excessive fuel consumption or engine damage. If any of the above symptoms are encountered, have your vehicle checked at an authorized NISSAN dealer. However, now and then you may notice light spark knock for a short time while accelerating or driving up hills. This is no cause for concern, because you get the greatest fuel benefit when there is light spark knock for a short time under heavy engine load. After Market Fuel Additives NISSAN does not recommend the use of any fuel additives (i.e., fuel injector cleaner, octane booster, intake valve deposit removers, etc.) which are sold commercially. Many of these additives intended for gum, varnish or deposit removal may contain active solvents or similar ingredients that can be harmful to the fuel system and engine. Octane rating tips In most parts of North America, you should use unleaded gasoline with an octane rating of at least 87 (except supercharger) or 91 (supercharger) AKI (Anti-Knock Index). However, you may use unleaded gasoline with an octane rating as low as 85 AKI in high altitude areas (over 4,000 ft [1,219 m]) such as: Colorado, Montana, New Mexico, Utah, Wyoming, northeastern Nevada, Technical and consumer information 9-5