Bob T

I have a 2013 V6 and have what's probably a newbie kind of question.

Do these engines, even when totally stock, automatically adjust the tune for the octane of gas you run in it?
In other words will my car perform better if I regularly run 91 octane compared to regularly running 87 octane?

Nuke

I know that the 5.0 will adjust and I ***-ume the 3.7L does, also. What does the OM say?

Even if it does adjust, you won't benefit nearly as much with higher octane on the stock tune as you will with a custom tune.

Bob T

The OM mentions improved performance for the 5.0 like you said, but nothing mentioned for the V6 as to how it relates to performance.
Here is a copy/paste from the OM:

• 3.7L V6 engine
Regular unleaded gasoline with a pump (R+M)/2 octane rating of 87 is
recommended. Some stations offer fuels posted as Regular with an
octane rating below 87, particularly in high altitude areas. Fuels with
octane levels below 87 are not recommended.
• 5.0L V8 engine
Regular unleaded gasoline with a pump (R+M)/2 octane rating of 87 is
recommended. Some stations offer fuels posted as “Regular” with an
octane rating below 87, particularly in high altitude areas. Fuels with octane levels below 87 are not recommended. Premium fuel will provide
improved performance and is recommended for severe duty usage, such
as trailer tow .

(...the OM doesn't have the wink in it, I took the liberty of adding that)

JimC

We were testing out an alternative intake manifold so had the chance to put the car on the dyno starting with the stock tune and then swapping to different performance tunes to get baseline before swapping to the new intake manifold (which was a total bust unfortunately, but that is a different matter).

We were surprised to find that with 93 octane the 3.7 did indeed adjust for the octane and we were getting much better RWHP than expected on the stock tune - in fact pretty close to the 93 octane tunes. So while the owners manual doesn't mention it, the knock sensors will cause the PCM to adjust just like the 5.0 does.

Bob T

Thanks for the responses guys.
JimC, your response leads me to another question.
Forgetting what octane is readily available at the typical gas station, what octane would these V6's really like for best performance?
I have a good understanding of the basics from past hot rodding but I'm totally new to these engines.
I believe that with just about any engine once you reach the point where you have enough octane to optimize the timing and the fuel, any more octane is a waste and not increasing performance. What is the ideal octane for a stock V6?

hogasswild

The ford engineerings also confirmed this in an interview conducted in 2010 by MMFF magazine. I always run with 93 octane.

13V6coupe

I get 2-3 mpg better mileage on the 93 vs 87 as a side benefit. But I can notice a throttle response and performance difference (better, much better) running 93. So the cost difference is kind of a wash yet you benefit from better performance

WindyMustang

Good summary and I get the same experience with my car...although the 93 R Bama tune I have does have a very crisp throttle response...

2011V6Nicole

+1 on the 93 R Bama tune

13V6coupe

I was talking pre having the CAI and bama tune...

But yes add those in and the difference is even more substantial

Definately worth the cost difference to run better fuel, stock or modified ! IMO