Which Gasoline Grade is Best for Honda Hybrid 2005?

Hello!

I recently bought a Honda Civic Hybrid 2005 and its User Manual says
that "Gasoline Grade should be 86 or higher", which means any grade
above 86 which could be "Regular 87", or "Mid-Grade 89" or even
"Premium 93" can be used, as I understand. If I use "93 Grade
Gasoline", will it do any harm to the engine? What are the pluses and
minuses in using the "93 Grade"? What would you recommend and why?

I thank you for your time and will appreciate your advise.

Regards,
SG

 

Just use the "Regular 87". Using higher octanes won't harm the engine, but
it will definitely harm your wallet.

 

They'll all run the same so go for the lowest octane from a station that
sells fresh and clean gasoline.

Older cars are more sensitive to the octane rating. Their
air-fuel/emissions systems are operated by mechanical vacuum controlled
valves that are out of adjustment without sea-level air pressure behind
them. You had to reduce the octane at high altitudes to compensate for
the extra EGR and retarded ignition timing.

Newer cars use several feedback systems so that the engine runs at its
best under a wide range of conditions.

 

Higher octane fuel, in fact, will lead to *less* gas mileage for that
car.

 

not necessarily. depends how smart the engine management system is. in
the "old" days before knock sensors and crank angular velocity
measurement, igniton timing had a fixed map. with the above sensors,
you have a base map, but also an algorithm that monitors these two other
factors and from that, it can calculate in real time a set of new
ignition characteristics to take maximum advantage of any particular
fuel. i would hope that the expensive "super econo" car's management
would be this smart.

 

not necessarily. depends how smart the engine management system is. in
the "old" days before knock sensors and crank angular velocity
measurement, igniton timing had a fixed map. with the above sensors,
you have a base map, but also an algorithm that monitors these two other
factors and from that, it can calculate in real time a set of new
ignition characteristics to take maximum advantage of any particular
fuel. i would hope that the expensive "super econo" car's management
would be this smart.[/QUOTE]

No, it has no need to do any such thing. It is designed to operate on
86 octane fuel. It has no need to "take advantage" of anything else.

 

No, it has no need to do any such thing. It is designed to operate on
86 octane fuel. It has no need to "take advantage" of anything else.
[/QUOTE]
but formulations change between producer, by country, by state, by
season, by law, by mistake... there's plenty of reason to use smart
management, and a by-product of that is being able to run any grade gas
to best advantage.

 

no, the *only* thing it has to do is prevent engine damage from knocking.

You don't program it to run any grade at that grade's best advantage.
For example, where does that stop? Can I put avgas into my Hybrid and
the programming will "take advantage" of that?

It's designed to run at 86 octane. Yes, the engine management computer
will prevent damage should lower octane fuel be present, but that's
different from saying it will change the engine parameters for more
performance if higher octane is present.

It doesn't do that.

 

IIRC the V6's will do better on premium petrol. They include sensors to
notice the reduced tendency to knock & will optimize timing to take
advantage of it. (been discussed previously on this NG)

 

there's more to gas than octane rating.

modern programs run each tank of gas according to each engine sensor's
output and how that complies with what the ecu knows it can do with it.
if its ability to read sensor results for avgas are within its
abilities to manage, then sure, it can run avgas to best advantage. if
it can't, it won't and i'm not trying to tell you i know how the thing
is programmed.

i'm not interested in a personal disagreement - i'm only interested in
the technology. i've stated what what i understand to be the current
state of the art, and that /does/ include ability to run different
grades of gas to best advantage. i'm /assuming/ this applies to the
honda because honda have the necessary sensors, ie. knock and crankshaft
angular velocity, [among others]. and they have a good mechanical
design. other than fuel/air charge & ignition, one other big thing in
the performance equation is combustion chamber design. basically, some
designs can only run well with high octane. honda otoh have a design
that fundamentally runs well with lower octanes, but burns higher
octanes very well too - something that's hard to do well the other way
around. from that perspective, the honda /should/ be able to take best
advantage of different grades if it's getting the necessary ecu input
and has sufficient "smarts" to handle it, hence my assumption.

but maybe you /know/ this is not the case.

 

The state of the art is that yes, that can be done. Does any car
company engineer that into its low end family car?

No.

 

Actually, Elmo's assertion is correct. Higher octane fuels have fewer BTUs
of energy by volume than lower octanes.

 

other way around, according to my bosch automotive handbook at any rate.
there, regular gasoline is rated at 42.7MJ/kg vs. premium at
43.5MJ/kg. at 1.054kJ per btu, that's...

 

other way around, according to my bosch automotive handbook at any rate.[/QUOTE]

Your handbook is wrong.

 

For Honda, yes. It's not a matter of the ECU adapting to the fuel.
It's a matter of having simple feedback systems in key areas. Honda
knows how to make simple and efficient ECUs like nobody else.

That said, octane doesn't change performance unless the ECU is retarding
the ignition and recirculating exhaust gas to avoid knocking at wide
open throttle. The HAH does it all the time at low throttle but who
cares? Exhaust gas recirculation is just as good as more octane for low
throttle.

 

Your handbook is wrong.
[/QUOTE]

maybe, but the bosch automotive handbook has been an industry standard
for nearly 30 years. if it /is/ wrong, you really need to write & tell
them.

in addition,

http://www.chevron.com/products/prodserv/fuels/bulletin/fuel_economy/

contains the passage:

"On average, the heating value of premium-grade gasoline is about 0.7
percent higher than regular-grade because premium-grade, in general,
contains more aromatic hydrocarbons — the class of hydrocarbons with the
highest densities."

admittedly, that's not a lot, and chevron go on to say that the consumer
cannot tell the difference, but the principle applies. it's also
[engineering] ballpark with the bosch figues which show a 1.8%
differential. in either case, the difference does not justify the cost
increment.

in looking for that reference, i was surprised how hard it was to find
references to btu ratings for gasoline, because when you buy natural
gas, it's rated in btu's per cubic foot so there's no "black magic" on
what you're getting for your money. with gasoline, that information is
all but absent. i find that extroardinary because there's really /no/
reason it can't be smilarly rated. except perhaps that it would make
oil companies more accountable...

for california residents, there's also this little nugget:

http://www.chevron.com/products/prodserv/fuels/bulletin/oxy-fuel/enrgycon.shtml

great. even less bang for the buck.

 

That's an error.

Google for it.

 

Well you had to know that throwing some oxygen into the mix wasn't
going to give you more energy. Pre-burned fuel, what a marketing
concept.

 

One of my great laughs was a few years ago when a drink salesman was at
my local deli and was pushing "Sports Water", i.e., water with extra O2.
I asked the guy how he differentiated it from hydrogen peroxide & got a
bovine stare.

 

I just did some digging of my own to be sure. Basically, the energy content
is the same between different octane ratings of gas...UNLESS...oxygenates
have been used.

Oxygenates (alcohols, ethers) reduce the energy content of the fuel mixture
because they introduce more oxygen into the mix. As the O2 sensor responds
to the increased oxygen content, the engine management system will increase
fuel delivery to compensate, hence lower gas mileage.

This from the Gasoline FAQ and from Wikipedia.
www.repairfaq.org/filipg/AUTO/F_Gasoline2.html
http://en.wikipedia.org/wiki/Gasoline

I've noticed through extensive record keeping that my Integra will deliver
an average of 2% lower gas mileage with 91 octane versus 87. The 91 octane
I use has no oxygenates, and yet I still get a fuel mileage reduction.