89 octane Factory specs.
92 or 93 octane would be the best for that engine.
87 octane is recommended
The 2004 Chevy Avalanche is designed to run on regular unleaded gasoline with an octane rating of 87. However, using premium fuel with an octane rating of 91 or higher may provide slightly better performance and efficiency, especially under heavy load or towing conditions. It's always best to consult the owner's manual for specific recommendations.
87 octane
93 octane
87 octane.
Regular Unleaded 87 Octane is sufficient. Buying any higher octane is a waste of money and will provide no benefit.
the best fuel would be 91 octane or premieum.
" regular " unleaded - 87 octane
87 octane should run just fine.
The block itself will fit, and your best course of action will be to retain the electronic controls/engine computer and all electrical components from the 1997.
The best way is to siphon the old out and pour new in.