[Norm51]

This topic pops up every few months or so on this forum. This is a link to a blog I follow (among others) for DIY tips for my ICE-powered vehicle.

Bottom line: Read (and follow) your owner's manual.

The author is a mechanical engineer, not a petroleum or automotive engineer, that just happens to be a gear-head. But I liked the way he explained things. It's important to read all the way to the end to get the full reasoning behind his answer.

Again, the bottom line is to follow the manual for best results.

We use as much Premium sun shine in our Volt as possible!

 

[Steverino]

Thanks, I'll take a look.

Meanwhile, here is our guide: http://gm-volt.com/forum/showthread.php?66842-Volt-Premium-Gasoline-and-related-topics-FAQ

 

[eric_n_dfw]

Tank in the Volt is so small that it really doesn't make enough difference to debate IMO. But in my other cars that have recommended premium, I've never used it. Computers adjust fuel and spark just fine. My 2012 Maxima SV probably got minute amount of performance loss and maybe 1 MPG less than usually, but I have a pretty heavy foot so I doubt it mattered much.

Same with my 2001 Acura RSX Type S which had a very high compression ratio: I used premium in it for a year and then dropped to regular and never noticed any change.

By the article author's own admission, the computer is not going to let the engine get damaged, you just lose some performance.

 

[mk2]

And follow on from Eric's sentiment, ICE performance is almost irrelevant in the Volt, so as long as you're regularly going through gas, put in regular. If it's going to sit for 6 months, put in premium.

 

[ravadac]

Is there anything radically different between the 1.4l range extender and the 1.4l cruze engine? They both have the same 10.5:1 compression ratio - yet GM recommends regular unleaded for the cruze vs premium for the Volt. As the previous poster noted : "the tank is so small it doesn't make that much of a difference", but I'd really like to know if it's more of a fuel stability thing or a detonation thing.

 

[chrisvillar98]

Mechanical Engineer, gear head Volt owner hear. In the days before computer controlled spark timing and knock sensors, you pretty much had to put in premium if you had high compression ratios. Similarly, in a low compression engine, using a higher octane than necessary tended to hurt your fuel economy because the effect of high octane gas is that it burns slower. Lower octane fuels burn faster. You want your fuel to burn as quickly as possible (without causing detonation) to get the most energy (and efficiency) out of each gallon.

Today, things are different. High octane engines, while they use a slower burning fuel, are more efficient because of the high compression. Much higher maximum cylinder pressures are built up. This equals power and torque. However, they will tolerate low octane gas. The knock sensors retard the spark preventing detonation. But this negates the efficiency advantage of high compression. So you're saving $ on each gallon but getting less usable energy out of each gallon. MPG will drop.

Which way are you better off? Conventional wisdom on this forum says that you will save more money (via more gas range) with premium than you will with 87 octane.

Test it for yourself. I'm sure we'd all be curious what results you get. Put in a tank of premium and run a round trip on cruise control. Then refill with 87 and repeat. Tell us what difference it makes in MPG.

 

[ewiggins]

I buy so little gas that I just follow the manual. Over 2.5 years that has probabaly saved me only $100.00. Not worth possible screwing up the engine and getting lower MPG. I doubt anyone will void the warranty by following the recommendations.

 

[Neromanceres]

Is there anything radically different between the 1.4l range extender and the 1.4l cruze engine? They both have the same 10.5:1 compression ratio - yet GM recommends regular unleaded for the cruze vs premium for the Volt. As the previous poster noted : "the tank is so small it doesn't make that much of a difference", but I'd really like to know if it's more of a fuel stability thing or a detonation thing.

The Cruze engine has a compression ratio of 9.5:1 and is turbo charged. The Volt engine is 10.5:1 and is naturally aspirated. The Volt and Cruze share most of the same components but have different cylinder heads and intake manifolds.

Below is the GM Powertrain link that gives a fair bit of details about each engine.
Volt is engine code LUU
Cruze is engine code LUV
http://gmpowertrain.com/VehicleEngines/PowertrainProducts.aspx

In hot or dense (close to sea level) air environments the Octane level may be important for detonation. The Volt and all GM cars have an automatic system to detect detonation and change the ignition timing to adjust (GM's system is proprietary [Thanks to Saab]).

From a fuel life perspective many (not all) 91 octane fuels do not have ethanol added. Ethanol is hydroscopic (absorbs moisture) which reduces the shelf life of gasoline. Fuels higher or lower in Octane than 91 typically do contain Ethanol.

So if you live at cooler/higher altitudes and run through a tank of fuel at least every few months you shouldn't notice any difference with regular 87 Octane fuel in the Volt.

As I've stated before the Volt was tuned to run best on 91 Octane so in my opinion deviating isn't worth it.

 

[Mister Dave]

Starting with "Do I Actually Need Fuel?"

Not much in most cases. And then...

From a fuel life perspective many (not all) 91 octane fuels do not have ethanol added. Ethanol is hydroscopic (absorbs moisture) which reduces the shelf life of gasoline. Fuels higher or lower in Octane than 91 typically do contain Ethanol.

Makes sense to buy premium.

 

[ravadac]

The Cruze engine has a compression ratio of 9.5:1 and is turbo charged. The Volt engine is 10.5:1 and is naturally aspirated. The Volt and Cruze share most of the same components but have different cylinder heads and intake manifolds.

Below is the GM Powertrain link that gives a fair bit of details about each engine.
Volt is engine code LUU
Cruze is engine code LUV
http://gmpowertrain.com/VehicleEngines/PowertrainProducts.aspx

Not all of the Cruze 1.4l engines are turbocharged and some indeed have a compression ratio of 10.5:1. Apparently only the Cruze LTZ had the 1.4T

 

[ravadac]

The Cruze engine has a compression ratio of 9.5:1 and is turbo charged. The Volt engine is 10.5:1 and is naturally aspirated. The Volt and Cruze share most of the same components but have different cylinder heads and intake manifolds.

Below is the GM Powertrain link that gives a fair bit of details about each engine.
Volt is engine code LUU
Cruze is engine code LUV
http://gmpowertrain.com/VehicleEngines/PowertrainProducts.aspx

Thanks for the information from GM. Almost every other site out there lists the Cruze engine with a compression ratio of 10.5:1. I'll take GM's word for it that the compression ratio is indeed higher on the Volt vs Cruze

 

[Neromanceres]

Not all of the Cruze 1.4l engines are turbocharged and some indeed have a compression ratio of 10.5:1. Apparently only the Cruze LTZ had the 1.4T

The Cruze has two engine options the 1.8L naturally aspirated (LS models) and the 1.4L Turbo. The 1.4L Turbo comes on the LT, LTZ, ECO and RS models. In Canada the 1.8L is standard on the LT models but you can option the 1.4L Turbo.

The 1.8L engine has a compression ratio of 10.5:1. Engine code is LUW.

 

[Steverino]

Thanks for the information from GM. Almost every other site out there lists the Cruze engine with a compression ratio of 10.5:1. I'll take GM's word for it that the compression ratio is indeed higher on the Volt vs Cruze

Will you also take GM's word that their engine should use premium? : )

There are four ongoing Volt "religious wars": Premium vs. Regular, force automatic brake lights when in Low, power button location/tactile feel for blind "dash stabbers", and aerodynamics vs. comfort (air dam scrape noise, windows down drumming).

 

[eric_n_dfw]

From a fuel life perspective many (not all) 91 octane fuels do not have ethanol added ... Fuels higher or lower in Octane than 91 typically do contain Ethanol.

This is the first I've ever heard of this. I don't think it's true where I am in the DFW area as all pumps say they have up to 10% ethanol with no differentiation for the different grades.

I'll pay closer attention the next time I'm at a pump because if it is true, I'll definitely be using it for my lawn mower and trimmer. It would be much cheaper that the small can's of pure stuff I buy at Home Depot or Lowe's. (ethanol eats the plastic fuel lines on those)

 

[eric_n_dfw]

... replying to myself...
I guess it depends on where you live: http://www.bellperformance.com/blog/bid/110140/Does-premium-gas-have-ethanol-in-it

 

[Mister Dave]

up to 10% ethanol

"Up to" means it could have none.

 

[eric_n_dfw]

"Up to" means it could have none.

True, but it doesn't specifically say that premium doesn't. I believe the "up to 10%" label is a federal mandate for any gasoline with between 1% to 10% ethanol. The only places around here I've heard of that have 0%, guaranteed, are where you can get extremely high octane gas for racing or aircraft use (which I would venture a guess is much more expensive because of it's niche market)

 

[Mister Dave]

E85 which I use in my Silverado has the same label: "Up to 85% Ethanol". For all I know it could be pure Petrol, which is fine as long as I get the lower price that I get on E85. In fact it's probably better.

 

[eric_n_dfw]

E85 which I use in my Silverado has the same label: "Up to 85% Ethanol".

I think the "up to" is only there because they cannot guarantee what mix you will get at the pump, only that it shouldn't exceed that amount. (Although I've heard stories of people getting much higher than 10% at an "up to 10%" pump and it killed their engine)

I'm curious, do you know what kind of mileage does your truck git on E85 gas vs. E10? I've always heard that E85 drops MPG's down significantly because the ethanol burns so much hotter. I've never met anyone that actually used E85 until now.

 

[baragona]

This topic pops up every few months or so on this forum. This is a link to a blog I follow (among others) for DIY tips for my ICE-powered vehicle.

Bottom line: Read (and follow) your owner's manual.

The author is a mechanical engineer, not a petroleum or automotive engineer, that just happens to be a gear-head. But I liked the way he explained things. It's important to read all the way to the end to get the full reasoning behind his answer.

Again, the bottom line is to follow the manual for best results.

We use as much Premium sun shine in our Volt as possible!

Considering, that with a 9 gallon tank it is only 2-3 bucks more for each tank for premium and I only put about 10 tanks of gas in per year, I didn't think it was worth trying to save $20-$30 per year to use regular, with or without a mechanical engineer's endorsement...