Can unleaded gas be used in a 1966 ford mustang?
You can use unleaded in a low compression engine such as the in-line 6 and the 260. But use a high octane unleaded instead of regular unleaded. If however you have the 289, I am not sure on this engine. The 289 HO will require the use of a VSRP additive at each fill up. If your 289 has hardened valve seats and does not require a VSRP additive, you can simply switch to Shell V-Power (98 octane) or Shell Unleaded (95 octane) straight away. If you find that your Mustang tends to run hot then you will need to readjust the fuel/air mixture on the carburetor for the modern unleaded fuel.
