For my 98 Civic DX, the most agreeable choice is Premium gas for the summer and Regular for the winter... In the cold weather, there's less chance of mis-fire and perhaps winter blend also plays a factor. In the summer, in a effort to save $$$ I'll top-up with Regular if the tank is already half full of Premium gas (the combination has an adequate amount of octane to avoid 'pings' for my 98 DX engine). My two favorite gas station is ESSO and Shell. For the Regular gas (87 Octane) the ESSO seems to have an higher Octane count then the Shell but the Shell seems to get slightly better mileage. However, the difference is so minuet, I could be imagining the variation. When comparing fuel consumption between Premium and Regular, My car return about a 4% variance between the two fuel types. Note, my 98 DX Hatch doesn't have any sophisticated knock sensor, so it's totally at the mercy of the Octane count in the fuel. I don't know much about the 05 Civic (other then that my 98 Hatch is noticeably faster...probably do to the fact that my Hatch is LEV while new Civic is ULEV). Personally, for the 05 Civic, I'd use Regular gas (assuming it's consumption is equivalent or better then the Premium) and switch to Premium when entire exhaust system get replace for some performance enhancement. Pars 98 DX Hatch
And how did you determine this agreeability? It's not fuel injected? Or has your knock sensor come unplugged or become defective?
When mis-firing the engine will exude an un-agreeable amound 'pings' (or engine knocks). This happen in the summer but not in the winter (assuming 87 Octane, Regular, fuel is used). I wasn't aware that a knock sensor was mandatory for a fuel injected engine. If my 98 Hatch has a knock sensor, if most have an extremely tight operating range (considering that it will not retard the timing enough to avoid pre-ignition for the recommended fuel...luckily, the high-strung setup suits my more aggressive driving style). Pars
If it was sold in Canada or the US it must meet OBD-II specs and would have a knock sensor. It may be inoperative, or your ignition timing is grossly misset.
It (98 Civic) can get 700km/tank (in the summer) and has been dealer maintained since new. The car's tuning is on the ball, it just doesn't have the kind of knock sensor found in other engines that are more forgiving. It's also a LEV rated vehicle, so the ECU is not antiquated...but I don't know if it's OBD-II compatible. Considering that my mileage is in Hybrid territory, I'm not complaining. Pars
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Well, that link points out the difference of Octane rating specified by Honda and the Octane ratings posted on gas stations: I read my Honda's Owner's Manual and it says to use 91 "RON". What's that? Isn't that the same as what the pump sticker says? Not necessarily. That 91 RON is the same as 87 pump octane. The numbers quotes in the paragraph above are actually pump octanes. There are two methods used to determine the octane rating of a gasoline: Motor Octane Number (MON) and Research Octane Number (RON). RON is the higher of the two. Almost everywhere in the world, a gasoline is referred to by its RON rating. Here in North America however, the MON and RON are added together then divided by two to get what we call the Anti-Knock Index, or AKI, or "pump octane". So the formula is: (RON + MON) / 2 = AKI That's why 91 RON is the same as 87 AKI (pump octane). 91 AKI would be more like 96 or 97 RON. Britain has recently re-legalized leaded gas, and "4-star" 97 RON is available once again. Personally, I like to use the medium grade gas for my '94 Accord LX that is posted as 89 at the gas pump, using the (R+M)/2 method of calculation. I figure that should be well above 91 RON that Honda recommends though I still sense some pinging on hot days. I'm not sure if it's because the pumps posted Octane numbers are inflated or the engine timing is off specs. R. P.
my 98 hatch is completely OBD2 compatible. i got the scantool for it, even. the port is under the bolster near your left knee, i think. bout 2" by .75"
Where did you buy your Honda? Checking my daughter's 2003 Civic bought in Canada, the owners manual states: " Your Honda is designed to operate on unleaded gasoline with a pump octane number of 86 or higher" I think quoting a RON rating to customers who don't know what it means is grossly misleading. I wonder where and when Honda did so, and for how long?
