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87 Octane?

This is a discussion on 87 Octane? within the Mustang GT350 General Discussions forums, part of the Mustang GT350 Forum category; I’m considering getting a GT350, which would be my daily driver. I came across the following article, and was wondering if there’s any truth to ...

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Thread: 87 Octane?

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    I’m considering getting a GT350, which would be my daily driver.

    I came across the following article, and was wondering if there’s any truth to it :

    https://www.google.com/amp/s/www.hot...nd-gt350r/amp/

    The article mentions “The 5.2L engine was designed for 93-octane fuel, but will run on 87 octane with only a 15hp decrease in peak power.”

    Although I notice the manual specifies 91 as a required minimum, has anyone tried 87? While obviously I can afford the extra $500/ year for 91, it could make for a nice selling point for the wife😂. My inclination is that 87 would not result in pre detonation in the lower rpm range during the commute to work, but perhaps it’s not worth the risk.

    Serious input only please, don’t lecture me with “if you can’t afford $500/year you don’t deserve to own one”.

    Thanks!
    Last edited by 3ntr0py; 02-05-2019 at 02:40 PM.

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    Member tex929rr's Avatar
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    The owners manual actually says you void your warranty by running lower octane fuel. I’ve had a half dozen bikes and cars that call for premium fuel and the GT350 is the only one with that warning.

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    Last edited by tex929rr; 02-05-2019 at 03:22 PM.
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    Valid point. I assumed Motor Trend would be a reliable source, but if the owners manual says it will void your warranty, it’s not worth the risk lol
    Steve49 and 03reptile like this.

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    I wonder if it invalidates your warranty if its an emergency situation. I think it should be fine if you are in a situation where the only gas available is 87, and you fill up enough to get to a station with premium. This seems like a very valid scenario. Just as long as your not doing it regularly. I think if I had the option, I would put 87 in the tank. Better than being stranded.

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    Quote Originally Posted by DewmsEleanor View Post
    I wonder if it invalidates your warranty if its an emergency situation. I think it should be fine if you are in a situation where the only gas available is 87, and you fill up enough to get to a station with premium. This seems like a very valid scenario. Just as long as your not doing it regularly. I think if I had the option, I would put 87 in the tank. Better than being stranded.
    I think in practical terms the odds of it invalidating your warranty are about as likely as the odds running a few gallons of 87 octane gas actually damaging your engine - negligible. But I’ve never seen that language in any vehicle manual before. I just thought the OP should know.

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    Senior Member DCShelby's Avatar
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    Running 87 in a high compression engine will give it severe knock and detonation since it can’t pull enough timing out to prevent early combustion due to compression only. If you are out of gas I suppose you might be able to use a little bit, but I would not.
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    Member DewmsEleanor's Avatar
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    Quote Originally Posted by tex929rr View Post
    I think in practical terms the odds of it invalidating your warranty are about as likely as the odds running a few gallons of 87 octane gas actually damaging your engine - negligible. But I’ve never seen that language in any vehicle manual before. I just thought the OP should know.
    I think you're right here. Kind of a "don't see don't tell situation" I would guess. I totally agree with pointing out the Owner's Manual language, we definitely should all be aware of things like that. I will just say I may or may not have run out of gas after a spirited track day and had to put a gallon or two of 87 octane into the engine to get to another station. I had zero issues with the engine doing this. The ECU is going to pick up the knocks or misfires and dynamically change the timing to deal with that, but as a long term solution, just no.

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    Senior Member HellOnWheels's Avatar
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    Quote Originally Posted by 3ntr0py View Post
    I’m considering getting a GT350, which would be my daily driver.

    I came across the following article, and was wondering if there’s any truth to it :

    https://www.google.com/amp/s/www.hot...nd-gt350r/amp/

    The article mentions “The 5.2L engine was designed for 93-octane fuel, but will run on 87 octane with only a 15hp decrease in peak power.”

    Although I notice the manual specifies 91 as a required minimum, has anyone tried 87? While obviously I can afford the extra $500/ year for 91, it could make for a nice selling point for the wife. My inclination is that 87 would not result in pre detonation in the lower rpm range during the commute to work, but perhaps it’s not worth the risk.

    Serious input only please, don’t lecture me with “if you can’t afford $500/year you don’t deserve to own one”.

    Thanks!
    I always ran high octane gas in my 1989 Ford Escort GT because it burns cleaner. Even with the 4 banger, that car never let me down and a couple of years back I ran into the girl it was sold to. It's still on the road.Name:  escortfront.JPG
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    2020 Shadow Black, Carbon Fiber Dash, Technology Pkg., Handling Pkg.

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    I've only filled up with 93 but.... I'm now interested in 91. I can fill it up with 93 when I'm feeling spirited

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    93 or 94 only in mine. Car was designed for hi octane.

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