Premium fuel or Regular? GT Coyote V8

[Trackaholic]

If you want peak performance, use the highest octane you can stomach and get a tune for that amount.

If you want lowest running costs, use 87 and sacrifice a bit of power.

I use 91 since that's pretty much all we get in CA.

-T

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[B Gordon]

I run 87 because even though mine is a GT it gets driven slow and easy.
After getting the car and checking out threads somebody somewhere did a direct test with factory tuning and 87 & 91 octane and figured out that I am giving up 7 HP.
428 is plenty for me.

When I was making the choice on which Mustang to buy the decision was made to stay away from a turbo and the only trim level available as a 6 cylinder was just a bit too sparse for me. Maybe some others have a GT because it is whiz bang fast and so wants each and every horsepower available but I would have been happy with 300 HP.

 

[WildHorse]

If you want the lowest running costs then why buy a GT?
Btw.. what does it say inside the fuel filler door? Mine says 91 for my GT.

 

[Hack]

There's nothing inherently wrong with 87. How would gas with less detergents make your engine blow up sooner? Use a little logic here man.

Please re-read my post and show me where I said anything about blowing up? I was responding to the detergent/injector life comments.

 

[WaltA]

I don't know if anyone has read this, but it does specifically talk about the Mustang GT.

http://money.cnn.com/2017/12/12/autos/aaa-premium-gas-study/index.html?iid=ob_article_footer

 

[Dr. Norts]

I don't know if anyone has read this, but it does specifically talk about the Mustang GT.

http://money.cnn.com/2017/12/12/autos/aaa-premium-gas-study/index.html?iid=ob_article_footer

Fake news.

 

[Ebm]

.

Please re-read my post and show me where I said anything about blowing up? I was responding to the detergent/injector life comments.

This is your quoted post from before. :lol:

You're a good salesman. You make me wonder how my '99 F250 and '03 Explorer have managed to get a 1/4 million miles each on 87. Surely that crappy 87 octane fuel would blow up my engine completely in that many miles!

 

[B Gordon]

If you want the lowest running costs then why buy a GT?
Btw.. what does it say inside the fuel filler door? Mine says 91 for my GT.

Checked inside my filler door. It says;

Gasoline E0/E15

 

[sbrenskell]

I was wondering this as well. My V6 takes regular. I plan on putting premium in my 18 (unless my salesman tells me differently.)

 

[foqus]

I don't know if anyone has read this, but it does specifically talk about the Mustang GT.

http://money.cnn.com/2017/12/12/autos/aaa-premium-gas-study/index.html?iid=ob_article_footer

Pertinent sentence:

"It made the biggest difference in the V8-powered Mustang GT, which generated 3.2% more power using Premium."

 

[Zelek]

I was wondering this as well. My V6 takes regular. I plan on putting premium in my 18 (unless my salesman tells me differently.)

I wouldn't get your hopes up with a salesman. You'll probably get a tank of 87 octane in it when you pick it up. I'd stick with 93 as well.

 

[Hack]

This is your quoted post from before. :lol:

:tsk:

 

[morgande]

I can’t speak for the base V6, but the V8 has a very high compression ratio. I believe it’s 11:1.

Octane rating is an indicator of the fuel ability to undertake compression and timing without detonation. The higher the octane level, the more compression the engine can wistand and the more timing you can give it.

You never want detonation, detonation is bad! Modern-day cars have knock sensors that help identify detonation and stop it. How do they stop it? Timing. It’s extremely difficult to take the compression out the engine. So you adjust the timing to compensate.
Retarding timing stops detonation but robs power and efficiency.

As I said, the V8 has quite a lot of compression. It’s one of the things that allows this small 5 liter engine to make as much power as it does. To get the most out of that engine, you NEED to run the highest octane fuel you can. Granted your not gonna get any bennift from running 100 octane race fuel on a pump gas engine...but running premium fuel means I’m getting the most out of that compression without having to retard the timing. If you got the B8, run premium!

Ford knows people are cheap, and they built the engine to work with a lower octane fuel. But again, you can’t get something for nothing. So your loosing timing when you run that fuel.

If you have an ecoboost car, this issue is even worst because it’s direct injected AND turbocharged. Backing out timing on that engine has even worst effects

 

[Hack]

I can’t speak for the base V6, but the V8 has a very high compression ratio. I believe it’s 11:1.

Octane rating is an indicator of the fuel ability to undertake compression and timing without detonation. The higher the octane level, the more compression the engine can wistand and the more timing you can give it.

You never want detonation, detonation is bad! Modern-day cars have knock sensors that help identify detonation and stop it. How do they stop it? Timing. It’s extremely difficult to take the compression out the engine. So you adjust the timing to compensate.
Retarding timing stops detonation but robs power and efficiency.

As I said, the V8 has quite a lot of compression.

There's this thing called TiVCT on Fords. This means that our Fords can keep a valve open longer. Compression Ratio is a calculation of the piston's swept volume versus the volume of the combustion chamber when the piston is at top dead center. CR has something to do with an engine's tolerance for low octane fuel, but it isn't the only thing.

Yes, ignition timing can be adjusted, but the other thing that can be adjusted is valve timing. There is a term named dynamic compression that is used to account for valve timing when performing calculations to determine what octane fuel will be compatible with an engine. Open valves bleed off cylinder pressure and reduce the actual compression ratio of an engine. Fords can adjust valve timing on the fly.

The other thing to mention is that the impact of 87 vs. 91 is very small. Unless you are towing on a really hot day, you will not see any difference. Detonation is most likely to occur at low rpms and medium to high load on a hot day, so a couple fewer HPs are not likely to be missed. Detonation is less likely at higher RPMs where the engine's power peak occurs.

 

[morgande]

The other thing to mention is that the impact of 87 vs. 91 is very small....Detonation is less likely at higher RPMs where the engine's power peak occurs.

It’s a performance car. Get the performance you paid for. I rather have confidence that the engine is running at its optimum vs banking the checks and balances put into the ECU to run in a less optimum capacity hold true through the life of my ownership in the car. At least that’s my take.

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