50K+ Mile Owners - Intake Carbon Buildup

[brillo54]

Here in Canada, we are lucky to have ethanol-free 91 octane fuel at the shell gas station. Every other fuel in ALL of North America, including American shell 91 has ethanol in it. Ive tested all these different fuels in my BMW, including 87 fuel and found that it not only noticeably decreased performance and torque, but completely ruined my fuel economy as well.

I found that the ethanol-free shell is by far the best fuel I have ever tried. It was even better then Esso or Petro-Canadas 93/94 octane fuel!

Be careful with such blanket statements. My local Shell station HAS ethanol-free 91 octane (I checked with the owner when they converted from Country Mark brand to Shell, since CM had an ethanol-free choice). Some days it costs a bit more than 93 octane Nitro, some days less but at least $0.60 per gallon more per gallon than regular. For me it's not cost effective. YMMV.

 

[GJ-Molestor]

Be careful with such blanket statements. My local Shell station HAS ethanol-free 91 octane (I checked with the owner when they converted from Country Mark brand to Shell, since CM had an ethanol-free choice). Some days it costs a bit more than 93 octane Nitro, some days less but at least $0.60 per gallon more per gallon than regular. For me it's not cost effective. YMMV.

I see. I read somewhere on a forum that American shell 91 has ethanol in it, so I dont know..

For a car designed around 87 fuel like ours. Theres no point in using 91. But for cars the requirement 91 Ill happily pay the premium because the car feels awful with regular fuel.

On average, we pay $ 1.30 PER LITRE here in Canada. Id be god damn ecstatic to pay as much as Americans do for fuel!

 

[ColoradoDriver]

I see. I read somewhere on a forum that American shell 91 has ethanol in it, so I don’t know..

For a car designed around 87 fuel like ours. There’s no point in using 91. But for cars the requirement 91 I’ll happily pay the premium because the car feels awful with regular fuel.

On average, we pay $ 1.30 PER LITRE here in Canada. I’d be god damn ecstatic to pay as much as Americans do for fuel!

Yikes. That would be about what ~$5/gal?

I filled up with some 87 for $2.44/gal yesterday.

We have 85, 87, 91 here. I just put in the 87 since that's what the manual says to use. Though some days I wonder if I could get away with 85. I don't know how that works.

 

[dougal]

Here is a great test with dyno runs and mpgs by AAA that shows the Mazda is one of the few that actually does make a discernable difference to using higher octane fuels.

While in these experiments they are only testing the 2.0 Skyactiv-G in the Mazda 3, the same % differences can be had with all the Skyactiv-G motors, including the 2.5, and 2.5T Turbo models.

http://news.aaa-calif.com/internal_redirect/cms.ipressroom.com.s3.amazonaws.com/46/files/20168/Premium-Fuel-REPORT-FINAL2.pdf

Well, they only show 3 cars but yes, it does seem for the 2.0, using premium gas gives a 2.3% increase in HP. But no increase in gas mileage. And for 20% more in the cost. Not sure if it makes a difference.

 

[finch204]

Yikes. That would be about what ~$5/gal?

I filled up with some 87 for $2.44/gal yesterday.

We have 85, 87, 91 here. I just put in the 87 since that's what the manual says to use. Though some days I wonder if I could get away with 85. I don't know how that works.

You can get away with running 85 octane if you have no choice, like you need to fill up on a road trip but only 85 octane is available. The ECU will notice that it is knocking more often than usual and will detune so that you can continue driving with minimal knock. You will lose horsepower and mpg but you should still be able to drive it until you can fill up with 87.

 

[Red MC]

Be careful with such blanket statements. My local Shell station HAS ethanol-free 91 octane (I checked with the owner when they converted from Country Mark brand to Shell, since CM had an ethanol-free choice). Some days it costs a bit more than 93 octane Nitro, some days less but at least $0.60 per gallon more per gallon than regular. For me it's not cost effective. YMMV.

I read that approximately 5% of gasoline sold in the US is Ethanol free. But that was a couple years ago, so the percentage might be even smaller now. I haven't seen E0 available anywhere around here for many years, except for specialty race gas for motorsports and AV gas, neither of which I would put in my car.

I've wanted to buy some to fill my motorcycle tanks prior to winter storage, and also to fill my generator tank, but every time somebody posted a gas station in my area on pure-gas.org, it turned out to be bogus.

Yikes. That would be about what ~$5/gal?

I filled up with some 87 for $2.44/gal yesterday.

We have 85, 87, 91 here. I just put in the 87 since that's what the manual says to use. Though some days I wonder if I could get away with 85. I don't know how that works.

You could probably get away with 85 due to the higher elevation. After all, millions of people have been doing so for decades in all sorts of vehicles. But if it were me, I probably would do the same as you're doing and use what the manual says to use.

You can get away with running 85 octane if you have no choice, like you need to fill up on a road trip but only 85 octane is available. The ECU will notice that it is knocking more often than usual and will detune so that you can continue driving with minimal knock. You will lose horsepower and mpg but you should still be able to drive it until you can fill up with 87.

At higher elevations such as most of Colorado, 85 is generally as knock resistant or more knock resistant than 87 at sea level.

 

[erhayes]

Thanks for the find mazdadude:
A 2.36% difference in MAX isn't significant to the daily driver who doesn't use the engines red line as the shift points. In addition; AAA commented that anything less than 3% will not be noticeable to a driver. Those comments and the data for mileage and HP doesn't justify the increase in premium cost for me. Interesting information though. Ed

 

[GJ-Molestor]

Yikes. That would be about what ~$5/gal?

I filled up with some 87 for $2.44/gal yesterday.

We have 85, 87, 91 here. I just put in the 87 since that's what the manual says to use. Though some days I wonder if I could get away with 85. I don't know how that works.

Yes, but I forgot to mention that $5/gal is for 91 octane fuel. 87 octane checks in at a still ridiculous $4/gal.

Well, they only show 3 cars but yes, it does seem for the 2.0, using premium gas gives a 2.3% increase in HP. But no increase in gas mileage. And for 20% more in the cost. Not sure if it makes a difference.

In German luxury cars that require 91 octane, I found that fuel economy went down ALOT when testing 87 octane fuel. Using 91 octane fuel with ethanol affected fuel economy as well. By far the most efficient fuel was the ethanol free shell 91, which noticeably improved torque and fuel economy.

More usuable torque = less RPMs needed to get going which = better MPG, but for a car like our Mazdas which are tuned around 87 fuel, the difference doesnt seem that major.

You can get away with running 85 octane if you have no choice, like you need to fill up on a road trip but only 85 octane is available. The ECU will notice that it is knocking more often than usual and will detune so that you can continue driving with minimal knock. You will lose horsepower and mpg but you should still be able to drive it until you can fill up with 87.

Correct, but you want to avoid using lower octane fuel for extended periods of time, because the ECU will be constantly retarding the timing.

Thanks for the find mazdadude:
A 2.36% difference in MAX isn't significant to the daily driver who doesn't use the engines red line as the shift points. In addition; AAA commented that anything less than 3% will not be noticeable to a driver. Those comments and the data for mileage and HP doesn't justify the increase in premium cost for me. Interesting information though. Ed

For a car tuned around 87 fuel, no its not worth it. If you were to get an ECU tune for 91 octane fuel or try this with a car that requires premium, both power AND fuel economy will improve if you use ethanol-free premium fuel.

 

[GJ-Molestor]

I read that approximately 5% of gasoline sold in the US is Ethanol free. But that was a couple years ago, so the percentage might be even smaller now. I haven't seen E0 available anywhere around here for many years, except for specialty race gas for motorsports and AV gas, neither of which I would put in my car.

Ive tried many different fuels in my BMW, and my car ran so much smoother with the ethanol free fuel. It gave the engine a deeper more growly engine note, the car ran better, pulled noticeably harder and the fuel economy was MUCH better then before. I am never using ethanol fuel in my car again.

You could probably get away with 85 due to the higher elevation. After all, millions of people have been doing so for decades in all sorts of vehicles. But if it were me, I probably would do the same as you're doing and use what the manual says to use. At higher elevations such as most of Colorado, 85 is generally as knock resistant or more knock resistant than 87 at sea level.

Really? I thought that if anything, higher octane fuel would improve resistance to knocking? Why do Americans even have 85 octane fuel available lol. At least you guys dont pay anything for gas!

 

[murky]

Well, they only show 3 cars but yes, it does seem for the 2.0, using premium gas gives a 2.3% increase in HP. But no increase in gas mileage. And for 20% more in the cost. Not sure if it makes a difference.

Actually, it is in increase in fuel efficiency from which they deduce a hypothetical horsepower gain. From the experiment, the increase in horsepower is inferred from the ability to complete a fixed amount of work with less fuel.

 

[murky]

Ive tried many different fuels in my BMW, and my car ran so much smoother with the ethanol free fuel. It gave the engine a deeper more growly engine note, the car ran better, pulled noticeably harder and the fuel economy was MUCH better then before. I am never using ethanol fuel in my car again.



Really? I thought that if anything, higher octane fuel would improve resistance to knocking? Why do Americans even have 85 octane fuel available lol. At least you guys don’t pay anything for gas!

From your many posts it seems that you are either much more attuned to the subtleties of life than I, or are highly suggestible.

 

[GJ-Molestor]

Actually, it is in increase in fuel efficiency from which they deduce a hypothetical horsepower gain. From the experiment, the increase in horsepower is inferred from the ability to complete a fixed amount of work with less fuel.

Correct, and this is especially true with vehicles tuned for 91 and if you like to drive spirited. The premium fuel will practically pay itself back if its ethanol free.

 

[murky]

Correct, and this is especially true with vehicles tuned for 91 and if you like to drive spirited. The premium fuel will practically pay itself back if its ethanol free.

I don't think I'd be able to discern a sub 3% improvement in horsepower.

 

[GJ-Molestor]

I don't think I'd be able to discern a sub 3% improvement in horsepower.

You would. It depends on what sort of fuel you are using. I personally found that the ethanol free 91 made a far bigger difference in terms of performance then just regular 91.

Going from regular 91 to ethanol free shell, I noticed a solid 2-3HP increase. Now imagine going from 87 to shell 91. Ive tried it before myself, and the difference is quite large. Fuel economy improves by a lot too.

But like I said, no point in the Mazda unless you got a tune and like to drive spirited.

 

[Kedis82ZE8]

Not the best of videos and I personally have not noticed any difference with mine but still at just over 36k miles. I think the guy on the left used to work as a Mazda tech.

Not positive...but I think this is the intake cleaner he mentioned in video. Administered via a vacuum port on the intake.

http://www.granitize.com/portfolio/ad47-air-intake-system-cleaner

 

[GJ-Molestor]

Not the best of videos and I personally have not noticed any difference with mine but still at just over 36k miles. I think the guy on the left used to work as a Mazda tech.

Not positive...but I think this is the intake cleaner he mentioned in video. Administered via a vacuum port on the intake.

http://www.granitize.com/portfolio/ad47-air-intake-system-cleaner

Your best bet is to remove the intake manifold and walnut blast the valves or scrub em clean. Those intake cleaners are mostly a gimmick.

Do you shift at redline about once a week or so? That will delay the buildup of any significant carbon to well past 60k Miles.

If you drive very conservative and never rev the car hard, you will start seeing signs of buildup by 40-45k miles.

 

[Kedis82ZE8]

Yeah...I get on mine hard every couple days. You have to for safely merging around here. Even worse when caught behind someone merging onto freeway at 45MPH and traffic is moving at like 70+ in the slow lane.

 

[GJ-Molestor]

Yeah...I get on mine hard every couple days. You have to for safely merging around here. Even worse when caught behind someone merging onto freeway at 45MPH and traffic is moving at like 70+ in the slow lane.

Yea, your best bet is to do a nice slow pull all the way up to redline in like third gear, especially up an incline about once a week. As long as you dont excessively redline the car for no reason it will be healthy for a very long time.

My dad doesnt drive aggressively at all and we already started seeing signs of buildup at like 45k miles, and that was with me redlining the car a few times every couple months as well! The exhaust smelled absolutely terrible until I cleared out all the carbon. After 60k, note for a rougher engine note below 3k rpm, especially when shifting into second gear at low rpm. During this instance, you can hear an audible intake grumbling sound that goes away once you start to access the torque curve. The idle has become a little less smooth and fuel economy has gone up slightly.

 

[Red MC]

Really? I thought that if anything, higher octane fuel would improve resistance to knocking? Why do Americans even have 85 octane fuel available lol. At least you guys dont pay anything for gas!

Knock occurs when the combined temperature and pressure of the compressed fuel/air mixture exceeds the threshold of self-ignition at some place in the compression chamber before the spark.

Altitude is a factor in knock because the peak pressure that the fuel/air mixture reaches prior to ignition on the compression stroke is a function of intake air pressure. At higher altitudes, the ambient air pressure is lower, so the pressure of the compressed fuel/air mixture is also lower, so knock is less likely. That is why lower octane fuel at higher altitude can be as knock-resistant as higher octane fuel at lower altitude.

 

[Seabright]

Wait - are there reports of carbon buildup on these engines? Lots of noise, little data.