Can i put regular gasoline in a high test engine?

Question

I am looking at a 1978 ford thunderbird diamond julibee edition car. it has a 351 cleveland. it asks for high test gas but could i use regular unleaded?

Answer 1

If you have knock sensors then you can get away with that.

Most electronic ignition & fuel injected system usually have knock sensors (but not always).

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If you have carburetor & distributor with mechanical advance -then you do NOT have knock sensor and you CANNOT put in regular.

Good Luck...

P.S.  In cold winter (and not pulling heavy weight) you might be able to get away with lower octane gas.

Answer 2

You probably could get away with using 87 octane, but it could cause your valves to ping.

Regular gas will not harm the engine, but it will have a small decrease in horsepower. High-performance engines usually recommend 93 octane in order to get optimum performance.

Unless it says "premium fuel required," you could use regular.