# mix of regular and premium gas?



## FAQ (Mar 7, 2006)

I found that my 2006 Escape runs better without knocking while accelerating by using premium gas. But it costs much more than regular gas. Is it alright to use reg-premium-reg-premium gas alternatively?


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## Raylo (Feb 12, 2006)

Sure, no problem doing that. But I am surprised that you see a noticeable difference.


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## FAQ (Mar 7, 2006)

Raylo said:


> Sure, no problem doing that. But I am surprised that you see a noticeable difference.


Yes, it does run better. I searched the web for this knocking while accelerating problem. Switching to premium gas is one of the solutions.


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## wolfen1086 (Oct 4, 2007)

Cars that are designed to run on Premium will make a knocking sound when they run on regular, its called spark knock,the works case problem that I know of from this is screwed up plugs. but your gas mileage might suffer too, plus I have never run across the long term spark knock so I have no idea what else it could do to the engine.


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## Raylo (Feb 12, 2006)

Indeed, and most modern cars have knock sensors and computer spark retard that dials back the timing to avoid detonation at the expense of a little power. But even though I haven't looked it up I doubt an Escape specs premium gas.


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## FAQ (Mar 7, 2006)

Raylo said:


> Indeed, and most modern cars have knock sensors and computer spark retard that dials back the timing to avoid detonation at the expense of a little power. But even though I haven't looked it up I doubt an Escape specs premium gas.


I remembered when I searched for solutions, it did mention about timing too fast or mixture too rich. The Escape can be pretty peppy when stepping on the gas. Maybe that is the cause of it. Escape only asks for the use of regular gas.


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## Raylo (Feb 12, 2006)

This is a perennial topic in every auto forum I have ever been a member of. My opinion: if your maintenance is up to date it is very unlikely that you will get sufficiently bad detonation (pinging) on the recommended fuel to cause significant spark retard (and thus hurt performance). Keep in mind that the most efficient programming brings the timing right up to the max for the design and fuel and that is what Ford intends and, I'm sure, supplies. And a motor designed and intended for regular will not benefit in any substantial way from premium gas. But the bottom line is it's your $ and if you think you are getting 20 cets per gallon benefit by running premium, then go for it. Won't hurt anything except your wallet.


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## wolfen1086 (Oct 4, 2007)

Maybe its the gas?
well...fuel, it hasn't been gas in a hellofa long time.


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## Wrench97 (May 10, 2008)

Too lean, the timing too far advanced, (but the PCM controls the timing on all OBD II engines,) will cause a spark knock, long term it causes burnt pistons, the knock is from high cylinder temps starting combustion before the shark plug fires, when the plug fire the 2 explosions hit each other and cause the knock.


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## wolfen1086 (Oct 4, 2007)

That makes sense, so spark knock would be a VERY bad thing.


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## FAQ (Mar 7, 2006)

wolfen1086 said:


> That makes sense, so spark knock would be a VERY bad thing.


Then it's the money well spent because I don't hear the knocking when accelerating. But how does the high octane (only 4 octane difference) premium gas/fuel retard the advanced timing?


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## Wrench97 (May 10, 2008)

It does not the higher the octane the higher the flash point so the fuel does not ignite by the cylinder temp.
It may be worth having it checked out for a vacuum leak or a bad knock sensor, the PCM has what's reffered to as a learning curve, it'll learn over a number of key starts where the timing and fuel settings are so once moving to hi-test the PCM will learn the settings in order to go back to regular it'll have to relearn or you'll have to reset the PCM.


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## Raylo (Feb 12, 2006)

I don't think that a car designed for regular will typically be able to advance the timing beyond the stock calibration to take advantage of premium gas. It is usually just the other way around. If the knock sensors see a threshold level of pinging (a little is not bad) the PCM will pull timing back. We run TTS datamaster to check and tune our F body motors and you can see the retard events for a too aggressive PCM program. But there are no "advance" events. There is a programmed spark timing curve based on many input parameters and any PCM action retards from that if it sees beyond threshold knock.

Like Wrench says there is a lot of learning going on as well. Maybe it will learn and adjust how fast it makes retard actions if/when it does get pinging and be more aggressive based on history, which might vary from reg or premium gas? I'm not sure about that, though.

But if your motor and sensors are working correctly, and the gas is in spec, the slight pinging you hear should not be damaging.... unless Ford really screwed up. I don't think they make those kinds of mistakes, and I'm not even a Ford guy!


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## wolfen1086 (Oct 4, 2007)

FAQ said:


> Then it's the money well spent because I don't hear the knocking when accelerating. But how does the high octane (only 4 octane difference) premium gas/fuel retard the advanced timing?



Its only money well spend if you can afford it.


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