I just returned home from a 10 day trip towing my travel trailer/caravan. My 2010 Ford F-150 V8 runs on 87 Octane. Well, the next day I got the big kitty out of the garage and took it out for a little run up a local canyon. But first I needed gas.

After many fill-ups on the truck, after I put the card in the slot I punched the 87 octane button on the pump. It was not until I was leaving the station that I realized what I had done. Nearly a full tank of 87 octane gas.

The result? I noticed nothing different. Apparently the computer/spark timing/variable cam timing setup prevented any pinging. I also noticed no loss of performance. Hmmmm.

What I have done since is to fill up with premium as soon as I get down 1/4 tank. Better safe than sorry.

Tom

 

The only difference I noticed when I did the same thing is about a 2mpg drop in fuel mileage.

 

Many owners have deliberately or inadvertently fueled their vehicles with low(er) octane gas. Most report no difference at all or a slight reduction in mileage.

 

I run 87 octane exclusively in my '07 XK, and have consistently experienced better fuel economy when comparing back-to-back 87 octane vs. 91 octane.

I have had the same experience in an '05 Z06 Corvette; and an '07 BMW Z4.

My understanding is that 87 octane has more energy btu than 91. However, I add the caveat that if detonation occurs with 87 then ignition will be retarded and one will lose all the benefits of lower octane.

 

I run 87 octane exclusively in my '07 XK, and have consistently experienced better fuel economy when comparing back-to-back 87 octane vs. 91 octane.

I have had the same experience in an '05 Z06 Corvette; and an '07 BMW Z4.

My understanding is that 87 octane has more energy btu than 91. However, I add the caveat that if detonation occurs with 87 then ignition will be retarded and one will lose all the benefits of lower octane.

 

Have run 87 in my 2001 XJR for 8 years with no problems . Since I have not gone o higher octane I cannot attest to improved MPG.