premium fuel in a DI engine

Greetings, I own a 2014 chevy cruze with a 1.4 turbo and a 2013 Malibu with the 2.5 both DI engines. With much talk about carbon and such in DI engines is premium the way to go? I run premium in both engines, mostly Shell V poweer with an occasional Marathon or speedway stop all which claim to have 93 octane premium. The shell v power nets a consistent 35 MPG in the Malibu with other premiums only getting 32 MPG on average . My wife drives the Cruze and gets 35mpg as well but tends to idle the car alot before driving in the morning. The question to all this being is premium fuel a benefit in DI cars ?
 
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Yes, I think so. Try filling up with regular for 2 tanks and watch your MPG, I'd put money on a lower result. For decades many engines have had a wide scale of octane tolerance built in, DI engines with their high static compression ratios could only add to benefits seen from higher AKI. I doubt it will much affect intake deposits however.
 
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Deposits will have no benefit as there is no fuel wash like with a port injection. GM and Ford play with the timing to get a little backsplash on the valves. Latest designs from both show deposits but at very low levels. In the case of the Ecoboost 3.5 there is little impact long term. As far as premium... I run the cheapest swill I can find in both of my Ecoboosts. Run perfect and provide MPG in line with the EPA (22/26 on the Taurus and 17/18 on the F150). I experimented with Premium for a month in the Taurus and there was a slight MPG gain but not enough to offset the additional cost. I've got 76k of MPG records on the Taurus and it's pretty much flat across the last 4.5 years.
 
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My parents recently switched from 87 to 91 in their Ecoboost Escape (2.0L). Once they ran a few tanks through it - they noticed that gas mileage on my mother's daily commute went from 24.5 or so to a hair above 27. They also noticed that it doesn't seem to be lugging when it pulls a hill in 6th gear and that it doesn't always have to kick out of 6th gear on hills. My father doesn't like that the 6F35 paperclip transmission has to keep shifting all the time - and now it doesn't have to! The cost difference is ... nothing. Even to the ten thousandths of a collar.
 
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Upstate NY
Your Cruze isn't DI. It's port-injected, same as mine. That being said, it will benefit from running octane higher than 87 in the spring/summer/fall to prevent predetonation with the turbo. Your wife's MPG would go up if she drives the car instead of letting it idle. The 1.4T puts out very little waste heat, and will take forever to heat if left to idle. Like, 10 minutes and it'll be at 140-150*F. Best to drive it, even when cold. If heat is an issue, a aftermarket oil pan heater will greatly speed the warmup in sub-freezing weather. For the 2.5 in the 'Bu, premium can't hurt. If it's cheaper than 87 due to better fuel economy or if you like the additional power available, keep running it. For DI deposits, it's my opinion that oil selection will play more of a role than fuel grade. Having a full-syn oil in both cars changed when it needs to be should go further in avoiding intake valve deposits than premium fuel.
 

JHZR2

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The question you need to have answered is what is the maximum spark advance that the engines in question will support. For example, I know that my saab (not DI) will advance to the point of utilizing AKI 90 fuel. Beyond that, it's a waste. In NJ we get 93, but in some places I see 91 as premium. So DI or not, the question is about spark advance really. DI adds some combustion cooling characteristics, so there are some benefits there, but it's all mapped and the OEM knows what the design can take advantage of. That's what you need to figure out!
 
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North Bend
Originally Posted By: 94 saturn sl1 2000 saturn sc2
The question to all this being is premium fuel a benefit in DI cars ?
What does the car maker recommend for your specific vehicle?
 
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KC
I think so. My car seems to run leaner using premium based on UOAs. Which makes sense because in order to run high compression on 87 octane, they have to really richen the fuel mixture to keep combustion temps down and prevent detonation. the leaner AF ratio should lead to reduced fuel dilution (did for me). This can only help reduce the rate of intake valve deposit buildup.
 
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93 vs. 87 only matters if the engine has the hardware and software tuning to take advantage of it. Most turbo cars tuned to run on 87 can advance timing enough or do other tricks with the airflow and spark to affect responsiveness and MPG. A lot of newer DI engines seem to have the ability to as well. Give it a try for a few tanks and see.
 
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Parts Unknown
Originally Posted By: 94 saturn sl1 2000 saturn sc2
Greetings, I own a 2014 chevy cruze with a 1.4 turbo and a 2013 Malibu with the 2.5 both DI engines. With much talk about carbon and such in DI engines is premium the way to go? I run premium in both engines, mostly Shell V poweer with an occasional Marathon or speedway stop all which claim to have 93 octane premium. The shell v power nets a consistent 35 MPG in the Malibu with other premiums only getting 32 MPG on average . My wife drives the Cruze and gets 35mpg as well but tends to idle the car alot before driving in the morning. The question to all this being is premium fuel a benefit in DI cars ?
It's only a benefit when the car is tuned for 91 AKI from the factory (or aftermarket tune).
 
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Michigan
i actually received a email from a customer service rep for GM that both my cruze and my Malibu would benefit from premium fuel. I know both cars are more responsive to the gas pedal than they were with regular fuel.
 
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KC
Originally Posted By: 94 saturn sl1 2000 saturn sc2
i actually received a email from a customer service rep for GM that both my cruze and my Malibu would benefit from premium fuel. I know both cars are more responsive to the gas pedal than they were with regular fuel.
These modern, high compression engines have been fitted with nothing more than bandaids to run on 87 octane. I get the old school mentality that whatever minimum is recommended will be as good as it gets (I used to be one) but that just isn't true anymore. These engines are designed and engineered to run on 91+ and then patched with bandaids to make cheap americans happy.
 
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Originally Posted By: Finz
JHRZ2... How is this determined by a DIY'r?
JHRZ2 may jump back in with more specific information. Try to find a website / forum that pertains to your specific vehicle model or engine - someone there might know from experience. Or, look in your owner's manual/ask a dealer technician for recommended fuels. If they say 93 octane fuel, then the advance curve will accommodate that advance. If it's only 87 octane, then probably not. The problem sometimes arises when a person has a vehicle clearly designed for regular gas (87 or 89 octane). The manufacturer doesn't bother to include an advance curve for anything beyond that, so if you run a tank of 93 octane fuel, the extra energy is pretty much wasted. It runs okay, but not much benefit.
 
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KC
Originally Posted By: dave5358
Originally Posted By: Finz
JHRZ2... How is this determined by a DIY'r?
JHRZ2 may jump back in with more specific information. Try to find a website / forum that pertains to your specific vehicle model or engine - someone there might know from experience. Or, look in your owner's manual/ask a dealer technician for recommended fuels. If they say 93 octane fuel, then the advance curve will accommodate that advance. If it's only 87 octane, then probably not. The problem sometimes arises when a person has a vehicle clearly designed for regular gas (87 or 89 octane). The manufacturer doesn't bother to include an advance curve for anything beyond that, so if you run a tank of 93 octane fuel, the extra energy is pretty much wasted. It runs okay, but not much benefit.
DI, high compression engines WILL advance. My skyactiv says 87 is the only octane required. Mentions nothing about higher octane yet Mazda3 forum members have shown there is a timing advance with higher octane and my UOAs have indicated fuel mixture is leaned out on higher octane.
 
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10,008
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Upstate NY
Originally Posted By: dave5358
Originally Posted By: Finz
JHRZ2... How is this determined by a DIY'r?
JHRZ2 may jump back in with more specific information. Try to find a website / forum that pertains to your specific vehicle model or engine - someone there might know from experience. Or, look in your owner's manual/ask a dealer technician for recommended fuels. If they say 93 octane fuel, then the advance curve will accommodate that advance. If it's only 87 octane, then probably not. The problem sometimes arises when a person has a vehicle clearly designed for regular gas (87 or 89 octane). The manufacturer doesn't bother to include an advance curve for anything beyond that, so if you run a tank of 93 octane fuel, the extra energy is pretty much wasted. It runs okay, but not much benefit.
For the turbocharged Cruze at least, this is incorrect. It's pretty heavily detuned to run acceptably on 87. Exhibit A: a Trifecta or Vermont tune picks up 25-27 hp and 45-50 ft/lbs on 93 octane with no other changes made to the engine/intake/exhaust. Those tunes are fairly conservative to account for slight production and regional fuel differences. But when 18% more horsepower and 30% more torque can be gained on a 138 hp/148 ft/lb engine just by a reflash, that says that there's a lot left on the table in the stock tune. The owner's manual may say 87 octane. Being turbocharged, it will run better on 91+ octane. Less knock means it can run less enrichment to prevent knock.
 
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