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Old 2nd September 2006, 19:42   #1
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Default Why does Honda always recommend unleaded fuel only?

Well, this topic came into my mind when my car came back from its 3rd service at 10k kms..
the honda people had told me when i first bought the car that i should use unleaded fuel only..so for the first 3-4 tank fulls i did use that but then shifted to SPEED..i loved the change in throttle response..so used it till around 8k kms more..and my FE dropped day by day..down to 8.5 but i assumed that its all because of me just pulling the car too much on each gear.
But after my 3rd service 2 weeks ago...ive started using unleaded for some reason..just for a try..and well the change was not noticed in the first tank all i could feel a bit was throttle response..but then after 2-3 tanks of unleaded..my FE started to rise ..and now its 10!..and even the pickup is more smoother..the ride overall is more smoother

what i dont understand is that how can fuel with impurities be better for an engine rather than fuel without?
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Old 2nd September 2006, 19:59   #2
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lets just consider the octane ratings of the 2 fuels unleaded 87 and speed 91 ? i think,..maybe the Engine managent is set for normal indian fuel i.e 87octane
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Old 2nd September 2006, 20:48   #3
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I think, The Higher octane value leads to more power and cars speed up faster and drivers enjoy the surge..!
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Old 2nd September 2006, 22:29   #4
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hey man usually engines are tuned for their particular octane numbers .... thats why you experienced the change in fuel economy .... more over which vehicle are you driving ... give me more details ...
there cannot be a low fuel economy by using speed 91 make sure you drive the both fuel blends in the same way...
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Old 3rd September 2006, 01:16   #5
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i drive a vtec 1.5 ... 100 bhp
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Old 3rd September 2006, 02:20   #6
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Hang on!! Since when is high octane, leaded fuel? As far as i know, leaded fuel is almost fazed out.

I think you're getting confused between low/high octane and leaded/unleaded fuel.

I use "IOC 91 Xtra Premium" in my Vtec and it's awesome. The car performs better and is more FE.

U shouldn't see a drop in FE or performance with high octane fuel.

Try filling the same fuel from another gas station.

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Old 3rd September 2006, 02:26   #7
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Quote:
i drive a vtec 1.5 ... 100 bhp
Hmm, NHC Vtec eh? But it still shouldn't get affected by higher octane.

Shan2nu
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Old 3rd September 2006, 10:58   #8
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Quote:
Originally Posted by Shan2nu
Hang on!! Since when is high octane, leaded fuel? As far as i know, leaded fuel is almost fazed out.

I think you're getting confused between low/high octane and leaded/unleaded fuel.

I use "IOC 91 Xtra Premium" in my Vtec and it's awesome. The car performs better and is more FE.

U shouldn't see a drop in FE or performance with high octane fuel.

Try filling the same fuel from another gas station.

Shan2nu
i totally agree with every word of your post but then if you notice even when you open the fuel lid..it says unleaded fuel..and when i told the service guys that i use 91 oct fuel...they said "DONT" use it..no such reason..just recommended!

Isn't it supposed to be like..the higher the octane, the better the engine response and FE? (provided you drive the same way)
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Old 3rd September 2006, 11:24   #9
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Crv cap says use unleaded premium fuel only ???
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Old 3rd September 2006, 11:30   #10
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Unleaded gasoline only because of the adverse effects of leaded gasoline on the catalytic convertor. Like Shan said, you're getting confused between low/high octane and leaded/unleaded fuel.

Leaded gasoline would have an octane rating of 89, as against unleaded gasoline's 87. Higher octane ratings will need higher compression ratio's. What's the compression of the cars you are talking about?

Quote:
Originally Posted by v.tec
Isn't it supposed to be like..the higher the octane, the better the engine response and FE? (provided you drive the same way)
http://www.bajajusa.com/High Octane.htm

guys, read that article for higher-octane rated fuels. It's nicely explained. Pls copy the full line above with the link - the underlined part is only part of the link.

http://chemistry.about.com/library/w...abyb100401.htm

Last edited by condor : 3rd September 2006 at 11:45.
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Old 3rd September 2006, 15:42   #11
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Quote:
i totally agree with every word of your post but then if you notice even when you open the fuel lid..it says unleaded fuel..and when i told the service guys that i use 91 oct fuel...they said "DONT" use it..no such reason..just recommended!
Yes, but isn't high octane fuel unleaded as well?

And what do they mean by "no such reasons"? If they're so sure about not using high octane fuel, they should also be in a position to back their recommendations with technical explainations.

Yes, there's a limit to how high the octane levels can go as per engine specs but it can never harm your engine.

I found a diff when i moved from 87 to 91. But thats about it. I've tried 93 oct and the car didn't perform any better than with 91.

Like cars have an "Aerodynamic Wall", every engine has it's own "Octane Wall". Once you've reached that stage, you wont see a performance increase unless you tune your engine, such that it can profit from that sort of fuel.

My stock Vtec has hit it's octane wall with 91.

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Old 4th September 2006, 13:48   #12
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My guess for using the word "Unleaded" is thats the way it is labelled at fuel pumps - atleast the BP fuel pumps - which have the following monikers on the dispensers - "Unleaded", "Speed", and "Speed 97". Unleaded would mean "normal" petrol.

When I owned a OHC AT, the dealer also told me the same thing, when I complained of engine knocking (I too had started using Speed thinking it would be better for the car).
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Old 5th September 2006, 00:01   #13
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We have discussed it here.... http://www.team-bhp.com/forum/techni...ium-fuels.html (Honda and Premium Fuels) ... merge?
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Old 5th September 2006, 00:48   #14
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@avin(VTEC)
I have also experienced a drop in economy with speed 91. Initially it rose by a km or so and engine felt smoother n all. But for the past few months my economy has just been going down with it, to a abysmal low of even 7kmpl(yes i did murder the car but then the same treatment used to yield an easy 9 before).

I tried driving as normally as i can and mananged to hit 10.5kmpl at the max. Finally one day I got the "petrol with energy boosters".. sorry dun remember the exact name of the fuel or the oil comany(the one with the pure for sure campaign) ;-)

and my car did a 12kmpl. now it stays around that only.

So I am left wondering with one more question. Should the FE change by that much with premium fuels of different comanies???
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