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2016 ATS 2.0T AWD Sedan
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Discussion Starter #1
Do I need to run 91 or higher with every fill-up? Can I run 87 or E15(Ethonel/gas mix(88)), and put 93 in every fourth tank? This is my commuter car and it sits in a lot of Chicago traffic. Of course, since people are going back to work the prices seem to be rising again at almost $3 a gallon for 93 octane. Thanks for any input.
 

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2014 ATS 3.6L AWD Performance
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You didn't specify which engine you have, but if it's the 2.5L you won't need anything more than 87...ever. ;)

If you have the 2.0T, I think it's highly recommended that you use 91 consistently. If cost is a concern, the advantages of 93 vs. 91 may be negligible, especially if you're doing mostly commuter car duty.

There are others with more specific knowledge on this, and I'm sure they'll chime in! :)
 

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What does the owner's manual recommend for your car/engine/driving conditions?
 

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2016 ATS 2.0T AWD Sedan
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Discussion Starter #4
Sorry about that. I have the 2.0T. We actually have 91 as the highest Octane. The gas cap recommends premium. But the manual states you could use lower but the engine may start to knock. I won't think a couple of tanks of lower octane could do damage? But I suppose anythings possible.
 

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2015 ATS Sedan 2.0 Luxury/Brembo Package
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Boosted engines such as the 2.0 should get @ least 91 octane preferably 93. Yes its more pricey BUT your engine will perform better which equals better gas mileage City or Highway. A car is like an investment. Protect your investment.
 

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2014 ATS 3.6 Premium RWD, 2016 Corvette Z06, 2018 GMC Sierra Denali 2500HD Diesel
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With the 2.0T you should stick with 91 octane. The ECM will retard timing but that happens only AFTER it begins to knock, retard is based upon the knock sensor being activated.

Early production 2.0T engines had an unacceptably high failure rate from destructive knocking that damaged piston lands and rings, cooler temperature range plugs and a new ECM program were used to avoid this problem and because of that history I wouldn't do anything with a 2.0T that increases the likelihood of knocking which definitely includes insufficient octane (which is a measurement of how well the fuel resists explosive combustion rather than providing a smooth burn).

I realize that you are basing this octane choice on running it lightly in commuter traffic but during my frequent trips into and through Chicago it is very rare that I don't use high throttle at least once getting through traffic situations and that sudden high throttle input is the exactly the type of driving that will create significant knocking until the ECM retards the timing. That knock you hear is the sound of the fuel/air mixture explosively combusting like it would in a diesel engine however unlike a diesel engine the engine parts aren't designed to live in that sort of environment. Using 87 or 89 as part of a tank when nothing else is available is reasonable but regular use of octane below the proper level is poor and potentially expensive practice.

Rodger
 

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2013 ATS 2.0T AWD
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I have a '13 2.0. I use BP 93. Great performance as designed. By the way, with BP credit card I almost always get several cents off per gallon so my 93 octane price is well worth the health of the engine and its components. I've used 89 occasionally and while the 'pick up' is slightly less than with 93, I'd rather be an 'according to the manual' kind of guy. BP doesn't offer 91 here, just 87, 89 or 93.
 

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2015 ATS 2.0t AWD
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I wish I could find the article that GM posted about the Cadillac ATS 2.0t and carbon build up (I'll keep searching). It wasn't about octane as much as it was about carbon build up.... they concluded that the engine needed Dexos (Dexos 2) oil and to use premium fuel from a quality name brand station - avoid 91 cheap stuff, and use 92 or 93 if you can find it. Again, it wasn't about octane, but about the vapors from cheap gas with low detergent qualities that settled on top of valves after shut down. I just read the same discovery from Harley Davidson regarding their latest M8 engine and carbon build up issues. High detergent premium fuel is highly recommended.
 

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2014 ATS 3.6 Premium RWD, 2016 Corvette Z06, 2018 GMC Sierra Denali 2500HD Diesel
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Fuel choice seem to be increasing in most areas. My 2014 ATS has the 3.6 designed to run on 87 on which it does well although factory programming puts it into too high of a gear for low to moderate speed steep grades creating a light knock and I use the paddles to drop down one gear to avoid this; I found 89 octane also is sufficient to prevent the issue. My 2008 CTS with the first gen 3.6L direct injection behaved the same say. My 2016 Z06 has a supercharged 6.2L and it drinks the recommended 93 octane except that it gets a couple of tanks of 91 octane just before winter storage because 91 is the highest octane available here that is ethanol free; I drive conservatively once it has 91 in the tank. The Z06 revised factory tune does take advantage of 100 octane fuel which reduces the propensity to pull timing under track heat and its setup is a little different than the typical high/low octane map in most vehicles with 93 octane as both the normally recommended and also minimum octane fuel for normal use.

For the pickup, I have to pick and choose because most of the year I like running diesel/soy blend for the added lubricity which keeps the injection pump and injectors happy. In winter I patronize the two area stations that have soy free because even with anti-gel additives and the larger fuel filter heater in the 2018 soy blend still gels far too easily in very cold weather. The most convenient source of soy free can't be used in the pickup because it is "red dye" diesel which is road tax free, I use that in the generator and tractor but using that in a highway vehicle is an invitation for a very large fine for tax evasion.

One of the Japanese manufacturers sold an export version of their small pickups in part of the world that had a switch to select either low octane or normal. In the normal position, it acted like other vehicles with the ECM advancing timing to normal levels unless the audible knock sensor called for timing retard and this results in operation that often creates at least minor knocking until it becomes sufficient to trigger the sensor and even then the ECM will continue to try advancing the timing repetitively to the point of knocking. In the low position, the ECM ran only the low octane map but could still retard timing further if needed. This setup likely would run afoul of some obscure EPA regulations in the U.S. but it would be a nice setup for people who would like to be able to run their vehicle on a lower octane with far less potential damage from frequently having enough knock to trigger the knock sensor.

In short, think of the recommended octane and knock sensor setup as being much like the engine overheat protection built into the ECM. The system is designed to protect the engine from immediate destruction when operated outside of typical operating conditions but it doesn't mean that it is good for the engine to frequently hit the conditions that trigger these protective measures.

Rodger
 

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I wish I could find the article that GM posted about the Cadillac ATS 2.0t and carbon build up (I'll keep searching). It wasn't about octane as much as it was about carbon build up.... they concluded that the engine needed Dexos (Dexos 2) oil and to use premium fuel from a quality name brand station - avoid 91 cheap stuff, and use 92 or 93 if you can find it. Again, it wasn't about octane, but about the vapors from cheap gas with low detergent qualities that settled on top of valves after shut down. I just read the same discovery from Harley Davidson regarding their latest M8 engine and carbon build up issues. High detergent premium fuel is highly recommended.
Carbon buildup in the head area will increase the odds of pre-ignition and knock. In extreme cases, it slightly increases the static compression ratio due to reduced volume in the combustion chamber but the major factor is the carbon creates pointed "hot spots" that ignite the mixture before the plug fires causing the undesirable situation where the piston is trying to further compress an already rapidly expanding burning mixture.

This fuel/air mixture behaves something like "gun powder" in fireworks. Tear open a fire cracker and light the trail of powder spread from it and you get a line of pretty sparks but confined in the tight space of the firecracker you get the desired pop/explosion. In the car engine, the charge should ignite and burn smoothly across the mixture but when the pressure is excessive for the octane during this ignition/initial burn phase you get an explosion instead of a smooth flame advance.

Rodger
 

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I would buy premium based on the compression ratio. The 2.5 has an 11.3-1 ratio, I'm not sure what it is with the 2.0. Any time there is a turbocharger involved, premium should be used because it packs more air into the cylinder, which raises compression.
 

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2013 Luxury ATS 2.0T Manual
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My general rule on this particular question is that the recommended fuel is for the people who plan to keep the car for a long time and the minimum is for people who are leasing or not keeping the car past the warranty period. I remember reading that the manufacturers would actually LOVE for 95 octane to become the standard. If they could build the engine around 95 the fuel economy savings would more than make up for the higher price per gallon and it should pretty much eliminate low-speed pre-ignition (which kills turbo engines, especially when using lower octane fuels).
 

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2016 ATS 2.0T AWD Sedan
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Discussion Starter #14
Thank you all for the input. In Chicagoland, you can't find a gas station that doesn't have a 10% ethanol mix or 93 octane. Like in some states that have a lot of boating or snowmobiling that cannot run an ethanol mixture (Michigan). This wasn't so much about the money, part of it is I can't use the car to it's potential and coming from a Ford Fusion 2.0 EcoBoost which recommended 87 and the amount of miles (50 a day) for gas turnover, that it wouldn't really matter. And now in Illinois starting 07/01/20 there's going to be a 7 1/2% tax increase on gas. About 40 % of the price is tax and the average will be about $2.40 for 87. But on another note, I was told that turbo cars like the flex fuel. That's why I also asked about the e15 type of gas. Those in the States, have a safe holiday weekend.
 

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There's no such thing as flex-fuel (although some outfits are now calling E85 flex-fuel). Flex-fuel is a designation given to vehicles that can operate on conventional gasoline (primary hydrocarbon being burned is octane) or operate on E85 (primary hydrocarbon is ethanol). They use a sensor to determine the blend of fuel that's in the tank and adjusts the fuel and spark maps on the fly. Properly tuned, ANY car likes E85...you can make much more power than with gasoline, but at the cost of efficiency. Mileage typically suffers when using E85 versus gasoline. Typical fuels that are primarily gasoline (your 87, 89, and 91+ octane fuels) are now commonly referred to as e10 or e15 depending on the ethanol content (e10 = 10% ethanol by volume, e15 = 15% ethanol by volume). E85 is 85% ethanol, 15% gasoline.

Now, I haven't read the manual on the Ford EcoBoost-powered cars, but I find it highly unlikely that an auto manufacturer is RECOMMENDING regular 87 octane gasoline on a turbocharged car. Like Cadillac/GM, they probably RECOMMEND that premium (91+ octane) be used, but ALLOW the use of 87 by detuning the spark maps when knocking is detected (really a bad way to go, as potential engine damage can occur before the computer adjusts - would be smarter if they used a sensor to determine the octane in advance and switch to a low-octane fuel map rather than wait for detonation to occur).
 

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Discussion Starter #16
I thought it was odd as well but there have been many a discussion on the Ford Forum as well about what to run. But right from the owner's manual, "1.5L, 2.0L EcoBoost® engines, Regular unleaded gasoline with a pump (R+M)/2 octane rating of 87 is recommended. Premium fuel will provide improved performance and is recommended for severe duty usage such as trailer tow."
I will put in Premium fuel and like the manual states. Thanks again. (y)
 

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2014 ATS 3.6 Premium RWD, 2016 Corvette Z06, 2018 GMC Sierra Denali 2500HD Diesel
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I suspect that the EPA fuel economy and cost of operation classification is based upon the manufacturer's recommended octane so if your vehicle can run OK on 87 octane, the annual operating cost will be lower according to the EPA and that might be part of the Ford recommendation motivation. Both the CAFE and "sticker" fuel economy drive cycles do some odd things but neither runs the engine in an operating area where the better (for forced induction engines) higher octane would make a real difference during those drive cycles. The move to very light synthetic oil such as 0W20 recommended for many cars was heavily motivated by the ability to use this in the CAFE drive cycle where the light weight oil does make a significant economy difference in fuel mileage tests.

The same basic 2.0T is available in the Camaro and in that owner's manual the use of 93 is advised with as low as 87 being usable with the strong warning that knocking and engine damage can occur and the owner must be cautious of this and immediately switch to 93 if knocking is evident to avoid engine damage. Cadillac wants 99 octane in the 2.0T if it is tracked to account for the higher operating temperature and increased likelihood of knock.

If you are stuck in the middle of nowhere and 87 is all that is available then use it but otherwise you are relying upon knock sense/ignition retard to prevent damage.

I suspect if the design engineers at GM powertrain were writing the owner's manuals then the 2.0T would state 87 octane would be emergency use only.

Rodger
 

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Is the issue saving money? If you drive with very light throttle openings and never in boost conditions, you could probably get away with 87 RON fuel with no problem at all and save maybe $4-5 per tank. Personally, I drive like the old man that I am, and I use 93 religiously because occasionally I operate in slight boost conditions where knock is most likely to occur. Will a little knock hurt? Probably not, but I can afford the extra money so I stay with 93.

As far as octane goes, octane itself is a measure of a fuel's tendency to auto ignite. The higher the octane rating, the less tendency to auto ignite. It has nothing whatsoever to do with energy content or detergent additives. It takes a bit more oil to refine gasoline to get to 93 that's why is costs a bit more.

Finally, if you truly drive in basically idle or just off idle conditions, running 87 won't hurt. If you need a burst of speed from time to time, your engine may experience knock and the ECM will retard the spark advance until the knock goes away. At that time and only during that time will your engine produce a bit less power at a given throttle opening and maybe a slight deterioration in economy, but will you even notice it? I rather doubt it.
 

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I suspect that the EPA fuel economy and cost of operation classification is based upon the manufacturer's recommended octane...
Interesting you bring that up. When evaluating cars I always look them up on fueleconomy.gov as a quick way to see tank size and annual fuel costs compared to other cars I own or have owned. When I looked up the ATS 2.0T back in the day, all their numbers were based on 87 octane. I figured that was because Cadillac had an 87 minimum and 91/93 recommended. Recently my wife bought a Volvo S60 T5 (which is their base engine, 2.0T) and also has a minimum 87, 91/93 recommended, but on fueleconomy.gov, all the numbers for that car are based on running premium. I wonder if something has changed in the last few years.
 

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2014 ATS 2.0T 6spd manual Performance RWD
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Top Tier certified 93 is the only gas I put in my 2014 2.0T (build date 4/2014 which is the last month before production switched over to 2015 production). Hey Costco, take my money! I have also gone 1 (further) step colder with spark plugs, installed catch cans, make sure to use low ash full synthetic 5W30 oil, let the car reach operating temperature before getting into heavy boost, don't lug the motor (easier to control since my car is manual), and I try to avoid heat soak.

That sounds like a lot to think about, but I'm a car guy and a gear head so I take some pleasure in it haha. But the average person going to buy a turbo car is likely not going to know most, if any, of that info or care to. This is why I think this movement of going to smaller motors with turbo's for fuel economy is not a good idea long term. I have a theory that as more turbo cars fall into the hands of the masses of car owners that simply have a car to get around or don't take an interest or work on them, there will be a more significant failure rate overall and ICE cars will gain even more of a reputation for being unreliable and/or costly to maintain/fix. Thus entering more favoritism for the electric car.

I could be wrong, and I hope I am, but I could just see that happening with the way the automotive industry, as well as the driving culture in this country, is going.
 
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