Check engine light when 87 or 89 gasoline goes in

[Kc Saasy]

I have a 2017 Lincoln MKZ 2.0T AWD. I haven’t had it long. I’ve been seeing that you can put regular 87 gas in the vehicle. My issue is that every time I put regular or plus my check engine light comes on and I would have to burn the gas out until it goes off. I however don’t have this problem with premium, any reason why that is?

Edited November 11, 2021 by Kc Saasy

[bbf2530]

2 hours ago, Kc Saasy said:

I have a 2017 Lincoln MKZ 2.0T AWD. I haven’t had it long. I’ve been seeing that you can put regular 87 gas in the vehicle. My issue is that every time I put regular or plus my check engine light comes on and I would have to burn the gas out until it goes off. I however don’t have this problem with premium, any reason why that is?

 

Hi Kc and welcome to the Lincoln MKZ Forum. Your issue is difficult to diagnose over the Internet. This should not happen, as our vehicles/engines are designed to run well on 87/89/91/93 octane gas.

 

So the two distinct possibilities are bad gas or an engine issue.

 

So first...What brand fuels are you using when you have this problem? Are you using name brand fuels? Filling up at the same station/stations each time this happens?

I would start off here: Next fill up, fill with 87 octane at a name brand station (Shell/Exxon/Mobil/BP/Sunoco etc.).

See if the issue occurs. If it does not, you have discovered the problem and you need to switch stations.

 

Second...If you still get a CEL, drive to a big box auto store in your area that will read stored engine codes for free (i.e. AutoZone, O'Reilly's etc.), and have them read your OBDII system for any stored engine codes.

Post back with the codes, if there are any.

 

Keep us updated and good luck.

[TomV]

87 shouldn't be a problem. Need to figure out what CEL code is coming up.

 

Lower octane fuel has less resistance to pre-detonation, so your computer should be pulling back the timing curve when the knock sensor detects pinging.

 

After reading the CEL code, I'd probably pull the battery terminal and clear out any adaptive learning the car did on 91+ octane to see if that helps.