Any benefits to high octane

It's your money...spend it how you want. I run Premium 92 octane in my EcoBoost to get max performance out of the engine. All of Ford's HP claims on EcoBoost engines are with Premium fuel. Now....I have the lucky privilege
of working from home and my work also involves quite a bit of travel via the airlines. I don't average more than about 400 miles a month on my tow vehicle so, for me, the cost is negligible.

All I know is my truck runs better, quieter and gets 1 to 2 MPG better mileage on premium fuel. When my daughter borrows it she fills it with regular and you can tell right away. Yes I am at sea level and yes summer temps here are often over 100* so that may make a difference.

Bedlam wrote:
See these links about timing:

And both talk about the possible effect that too much timing advance can have on OVERALL ENGINE TEMPERATURE, not about it's affect on combustion chamber temperature.

Two things about that: If the overall engine temp is SO high that it makes a significant rise in the COMBUSTION CHAMBER temperatures, then it is REALLY hot and a little knock might be the least of your worries.

Secondly, once the overall engine gets really hot, simply retarding the spark, or other adjustments to bring down the overall engine temp will take a LONG time to have an impact on the combustion chamber temps.

I haven't had a lot of experience with engines overheating but the few I have seen start knocking bad about 3 seconds before there is a catastrophic engine failure......during which time an minor adjustment of anything is unlikely to help.

So to sumarize:
In general, ignition timing has NOTHING to do with PRE-IGNITION under normal circumstances. Spark knock and pre-ignition knock are two different things.

See these links about timing:

https://www.physicsforums.com/threads/ignition-timing-vs-heat-distribution-in-the-engine.701885/

http://www.automotiveu.com/SolvingOverheating.htm

mkirsch wrote:

If you reduce the temperature in the combustion chamber by adjusting the timing, you also affect the conditions under which pre-ignition can occur.

Wait ? What ??

Pre-ignition occurs BEFORE the spark hits and the temp at that point is most dependent on the compression.....and overall engine operating temp too a little bit.

I'd like to see a reference for this claim you make.

Not that an engine working harder with an overall higher temp is more prone to pre-ignition.....but that spark timing alone will affect combustion chamber temps enough to make any practical difference in PRE-ignition.

Sam Spade wrote:

wwest wrote:

Just how does the computer adjust timing to prevent pre-ignition...??

It appears that we have at least one person here who understands the difference between "spark knock" and "pre-ignition".

Or not, because pre-ignition is not only a function of compression ratio but also a function of the temperature in the combustion chamber. A cold engine won't have pre-ignition, while an engine that's at operating temperature and/or being worked hard will.

If you reduce the temperature in the combustion chamber by adjusting the timing, you also affect the conditions under which pre-ignition can occur.

Atlee wrote:
My manual says absolutely do not use E85 fuel. It also says don't use less than 87 octane, even in the mountain states that offer regular in 85 octane.

It recommends use 87 octane when not towing or hauling.

It also suggest performance may be improved if premium is used when towing and/or hauling.

I have a 2014 F150 Eco-boost 3.5L engine.

Your turbo can vary boost to to keep the air charge in the cylinders optimal even at altitude thus you will still need the same octane at altitude. Normal engine gets less dense air thus lower absolute pressure and less likely to try to knock/detonate

Follow OEM recommendation for octane. Today's engine control systems will adjust to most conditions. If you are running high compression, boost or temperatures, you will benefit the most from higher octane fuel.

BenK wrote:
Betcha Turtle even has some of these busted parts sitting on his work
desk...most of us boy racers have them...the 'ex' tossed out mine... [emoticon]
But I see them all the time at the speed shop counters... [emoticon]

There you go again Ben, bringing up bad memories. :B Yes I have a few very expensive aluminum "ash trays" around my place. And I don't even smoke. :B

To answer the OP's question. It depends. If the OEM say's it's ok to use regular fuel in the engine, then 90% you will be fine using regular fuel. Why 90% and not 100%? Because there can be extenuating circumstances that the OEM can't know about.

For instance. If you tow at a very low altitude in very, very hot weather you can run into some detonation problems. This is usually migrated by the puter going to an overly rich mixture. This is why you sometimes hear people with ECO boost engines say they get better mileage with premium fuel. They are no doubt towing in hot weather and possibly at a lower altitude. If they use premium fuel the engine doesn't see detonation and therefore does not flood the engine with fuel.

Bottom line is this. If you OEM says you can run regular fuel then do it. If you are running in some weird circumstances like very hot weather and low altitude then it wouldn't be a bad idea to step up the octane for a tank or two. :)

boshog wrote:

I believe you wanted "pre-detonation".

No I didn't.

That term implies a detonation earlier than you wanted......and you NEVER want a "detonation" inside the combustion chamber.