So this happened...

[Duane]

Trying to save a few bucks, I filled up my 2010 SHO with 89 octane gas today. Salesman told me it could even run on 87, but I haven't attempted that. As I go to pass a semi today, the car lurches and stumbles. Power finally comes online but the check engine light is flashing and now the engine has a shimmy to it. It eventually smooths out and the idiot light goes off. I pull the code when I get home - P0301 - Cylinder 1 Misfire detected.

Is this just because of the 89 octane gas??? Anyone else ever experience this?

 

[SHOdded]

Is your SHO tuned or stock? Might be time to change plugs. Gapped to 0.035 if stock, 0.030 if tuned. Unfortunately, #1 is along the back wall, passenger side, so a little difficult to get to. Pull that plug and check appearance & smell. Hopefully there's no fuel smell. Leaky injectors have been known to happen, so have to watch out for it.

Probably nothing to do with the gas, all cylinders should have had the same problem.

http://www.obd-codes.com/p0301

If everything checks out, give it some time, as there can be a short relearn-as-you-drive period after changing to a lower or higher octane gas. Fuel trims, timing advance etc. will change if you change the fuel type.

 

[SDSHO13]

Just for a comparison, I use 88 Octane, on occasion, and have never had a problem. We have three available octanes West of the Missouri River, in South Dakota. Regular is 85 (Do not use - warning label on pump states it can damage new cars - thank you State Legislature); Mid-Grade is 88 Octane and Premium is 91, which is my normal juice. All three have 10% Ethanol. Only one or two stations in my area have Ethanol free fuel and the price is out of sight.

 

[Duane]

Regular tune. Car has 100k miles. Yes, I am planning on changing the plugs soon. I'm sticking with 93 juice from now on.

Thanks for the responses!

 

[Duane]

Stock tune. Car has 100k miles. Yes, I am planning on changing the plugs soon. I'm sticking with 93 juice from now on.

Thanks for the responses!

 

[WojoMojo]

Run 91, that's what I run tuned and it runs perfectly on higher boost. 93 on stock tune isn't necessary. I used to run 89 octane stock all day and it ran perfectly. Definitely get plugs changed. Did mine at 50k and they were shot. Updated to sp534 motorcraft plugs

 

[vforrest]

This is my work car (2014 npp) so I have 8k on it in three months so I do lots of highway driving. Have tried 5 tanks of each 87, 89, (91-93) octane as an experiment and have not noticed any difference in highway mileage. I get 27-28...usually 27.4 for 73 mph highway cruising which I think is outstanding considering everything! When the car was sold to me the sales guy says it made to run on 87...I pick the car up with a full tank waiting for me...yup 87 oct. I don't track the car but with any of the fuels and I pressed on the fun in my right foot I never noticed any difference with acceleration.

When I have a tank which is 50-50 city/highway I'm at 22-23 on a tank...again pretty happy with that. The last test I wish I didn't have to bear is my winter driving and get to see how this AWD compares to past cars and how much the fuel mileage drops with the winter blend fuel.

I love the SHO so far...wish my mirror rattle had a fix...but I like!

 

[WojoMojo]

I'm up in northern MN where temps regularly drop below zero (usually 20 below is an average morning temp). I ran 89 octane this last winter and it worked pretty well. I'm tuned now for 91 and will probably stick with 91. Depending on how much more expensive it is I might switch back to stock and run 89. On winter blend fuel I see about 15 mpg combined (maybe 19 with longer trips), and that's with hardly any spirited driving because of bad roads. That also is letting it warm-up for a decent amount of time. Feel terrible driving it ice cold. Oil is like molasses at that temp and I don't want to wreck anything Especially since it feeds the turbos as well.

 

[SHOdded]

Time for 0W-30 full synthetic?