Motor Trend first drive of the Volt

Unofficial reports I've seen have better economy with the 91, but that could easily be do to background noise and variables. Whatever the improvement, it was generally not enough to warrant the price increase.

For a car like the Volt, a hybrid with a decent EV range, I can see the reason for using premium. High octane is usually used for high performance engines. However, if you only need a lower output for the engine, a required premium engine might be lighter than a regular fuel one. It might be worth it if it reduces the load the motors have to lug around. With a 10 gal tank, it's only $2 more to fill over regular, and for some owners that will be an annual expense.

I don't think that's what happen with the Volt.

What ethanol? Does the 10% mandate apply to higher octane fuels? If alcohol free, premium would be a deal compared to E10.

 

I had another thought about premium gas in the U.S. vs Europe. A 20 or 30 cent per gallon difference amounts to 10% in the U.S. That would be like an 80 cent per gallon difference in much of Europe.

Tom

 

There can be real changes in fuel economy on octane if the engine is tuned to work best on 91. I read some things years ago and it looked at a few vehicles tuned to 91 per factory. All of them had mild reductions in power but at least a couple got a few worse MPG. This is why I used premium in my last vehicle, which did specify it as preference.

Gas is more in Europe because of taxes and octane is a fixed cost. Whether a barrel of oil costs $30 or $150 the refining required to get from 87 to 89 and 91 is the same regardless. This is why there is typically a dime difference in the US for each grade when gas is $2 and also when it's $4.

 

premium fuel

Sorry to keep going on this tangent but C & D did a regular vs. premium test at http://www.caranddriver.com/features/01q4/regular_or_premium_-feature long ago. The (easily missed) test results at http://www.caranddriver.com/var/ezf...lication/f2278580f25a8574f14a6f653836b82d.pdf might be of interest.

It included cars that required and didn't require premium and even included a low-tech vehicle w/no knock sensors (and thus no idea what grade of fuel was being burned).

FWIW, my 02 Maxima pinged a bit, esp. in hot weather when running on "required" premium. My 04 350Z (same engine, but tuned for more power) had MUCH more explicit notices about using premium and even words to the effect of, if you have to get lower octane gas, don't fill it all the way and fill the rest w/premium, ASAP. I've never heard it ping.

Side note: There was also http://priuschat.com/forums/other-c...-fuel-grenaded-cadillac-srx-gms-response.html.

 

During these octane discussions it's important to not confuse power and mileage. Getting more maximum power from an engine does not necessarily equate to getting better mileage. In fact the opposite may be true. Many conventional automobiles get better mileage at high altitude where the thin air reduces the output of the engine, allowing an over-sized engine to operate at a more efficient throttle position (aerodynamic drag is also reduced, but that's not part of this discussion.) The now weaker engine opens the throttle, which reduces pumping losses.

Tom

 

True for the Prius as well.

 

True, but we also need to keep in mind that hybrid that spends most of it's fuel burning time in serial mode, doesn't necessarily follow the same rules as a traditional car. A traditional car is driven most of the time at part throttle. So most of that extra power from premium gas is wasted. In fact, the extra power could potentially lower mileage by causing the use less throttle and thus incurring greater pumping losses.

Maybe, with the hybrid, the greater performance of premium, in some way, improves the overall efficiency of the system. Except for the possibility of using a smaller, lighter engine, I don't see how, and then the resulting weight savings likely wouldn't make much difference.

I don't buy the required premium, and then I bought it less after finding this:
"All other mandatory ethanol states just allow clear premium unleaded gasoline for the exempted classes."
Alcohol free gas alone, could give a 10% increase to fuel economy over E10.

Source of the quote:
Ethanol Free Premium Coalition

 

GM decided to use a non-turbo cruise engine in the car. They then decided to not give the engine DI. If it had DI then the car would get higher mileage and be able to use regular gasoline. Someone claiming to be a gm engineer claimed the cruise and volt would get 10-15% better mileage with DI and increased horsepower. Someone else said DI would have added $1400/engine. car and driver has said it costs ford $200/engine. Atkinson valve timing which would also improve mileage and would not add that much to the cost, but it would require di or forced induction to keep hp high enough. So choosing a small engine, then not designing it for the application is the reason for premium gasoline and part of the reason for poor cs mileage. That guy claiming to be a gm engineer claimed that gm made this choice in 2007 thinking lower cost was more important than mileage. This is strange as they were still talking about 50 mpg cs mode well after the choice.

 

This is not a serious effort to penetrate the conventional car market. The Chinese and the Japanese are way ahead. Wait till the Chinese market a $14K hybrid in the U.S.
In the next year or two, the market will see more, cheaper Asian hybrids as we get closer to the higher mpg mandates in 2015. Watch for the pols to roll back those mandates.

 

I don't buy it. Volt's 1.4 liter engine makes 74 hp. Why do they need premium gas to get 53 hp/liter displacement? It should get over 70 hp/liter on regular gas, just check any other non-hybrids.

Gen2 Prius has 1.5 liter Atkinson cycle engine and it makes 76 hp. The Otto cycle version makes 108 hp using regular gas.

The original Volt concept was supposed to use 1.0 liter 3 cylinders turbo engine to make 85 hp. They now think 1.4 liter is too small for the Volt?

 

First the Chinese have to release something in the US. Next, a $14k hybrid? I'm not holding my breath. There is a quality standard US consumers demand and that laws demand that the Chinese have no experience with meeting.

Because they compromised. A $41k barely-mid size 4 seater with an aim of being easy on fuel use and they make you put in premium, it's almost unbelievable. I wonder how much they really have saved and if it's worth the bad PR it will give them. All of the message board rants aside between people who will never buy one one way or the other I guarantee it will get some surprised looks from people told by their salesman that it requires premium and doesn't even get 40 after the battery. You can't excuse that away.

 

They aren't the same engine, though. The links above from C&D show that premium vs regular can be significant depending on application.

 

My honest guess is that it gives the thing better power or MPG, but probably not much and they're mostly hoping people will forget about the fact it runs on premium.

 

Premium gas might be, depending on state, ethanol free, even if 10% is in the regular. Pure gas is good for 3% to 10%, maybe more, increase in fuel economy over the 10% ethanol regular most people put into their tank. Not only does it get better mileage, there isn't the concern about the ethanol absorbing water and undergoing phase separation.

If a Volt owner does have access to ethanol free premium, they'll likely see better real world mileage with it. If they rarely burn gas, then they will less likely have problems from older fuel in the tank. Those seem to be legitimate reasons to require premium. It's just a shame GM didn't use a smaller, tightly tuned, engine to take full advantage of the higher octane.

 

I am not sure if the octane affects the emission. As I posted here, Volt's exhaust and evaporative emissions do not look good.

 

It might be. Mandatory 10% ethanol requirements are state level laws. Within those states that mandate it, there are exemptions to the mandate. Aviation gas is one such exemptions that is nationwide. Other exemptions vary by state. There's a hand full of ethanol free stations in central and western Pennsylvania. I'm guessing for boaters, but the exemptions can also be for 2-cycle engines or classic vehicles.

Of course, even if the premium gas is exempt from a mandate, the refiner may add it for an octane booster. Then there isn't necessarily and requirement to label pumps with ethanol content.

I prefer ethanol over MTBE, but, once again, politics is overriding logic and evidence for it as a fuel. The EPA is calling for 15% in gas, but refiners aren't going to do it until they get protection from liability for adding it.

Some of my info comes from this biased source:
Ethanol Free Premium Coalition