By on April 9, 2009

Saad writes:

Mr. Mehta, how do you measure the octane rating of fuel? I have a 2008 base-model Honda Civic, with the i-VTEC 1.8L 4-cyl. It is the India-Pakistan-spec Honda Civic and is similar to the one in the US. Although it does not require premium fuel, it is recommended and I’m worried we might not find good quality petrol in the rural countryside.

Where we are going, the only signs of civilization are bombed ruins from a war in ’71. And I am weary of regular already. In the Pakistan summers, it gets really hot over here (being a Desi yourself, surely you must know, and you’re in Texas!). If regular is used while the air conditioning is on the engine timing retards terribly and it sounds as if the pistons are colliding with the valves at nearly every sudden throttle tip-in.

We have used Octane Boosters before when premium was not available. We did notice a slight difference when we used octane booster (God, I’ll have to purchase another STP product), but that could be a placebo effect. If Octane Booster raises the octane of non-premium fuel (x) by (x+1), and if premium in the city has an octane rating of (y), how will I know when (x+1=y)? And are they harmful to the engine?

I’d also like to take a small sample of fuel from the pump and somehow measure its propensity to resist knock. If it is a high rating that’s roughly equal to the rating of premium fuel in the city, we’ll use it. Is there a way to do so quickly and easily? Or will I have to build an Inflat-a-Lab to bring along with us?

Sajeev responds:


A US-spec Civic needs regular 87-octane fuel, which means nothing in Pakistan. The USA uses PON octane ratings, other countries use RON or MON. As far as I am concerned, these might as well be called Amar, Akbar, Anthony. And if 1970s Bollywood references don’t work for you, this website will do the trick.

The first thing to do: find out what octane rating is used in Pakistan. (In this, Google is not my friend.) Then ask the questions (presented here) to the people in charge of distributing gasoline to the country, to get a rough gauge of the octane differential between urban and rural filling stations.

From there, look at the “premium” octane rating you normally use in the city and ask what octane is sold elsewhere in the country. You can quickly find the octane deficit (y-x=?) and compensate with bottles of octane booster. Sadly, I suspect you will need a crate of octane booster to keep your Civic’s knock sensor from working overtime.

If you hear anything more than a light tapping, get your foot off the throttle and only use the bare minimum. Also, as you almost suggest, limit the use of the air conditioning (e-mail me for Piston Slap liability release forms).

I mention these more elementary “solutions” simply because I don’t know of a quick, simple way to test gasoline’s octane ratings on the fly. The best you can do is

And if possible, please tell us when you will be making this trip, so we can purchase stock in the Octane Boosting manufacturer you’ll be favoring with your custom. Best of luck!

[Please send your technical queries to [email protected]]

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15 Comments on “Piston Slap: Mixing Masala Edition...”

  • avatar

    As noted above, the US (and Canada) both use PON, which is more commonly referred to as AKI and that is usually expressed on your neighborhood gas station’s pumps as R+M/2.

    Just about everyone else on the planet uses the RON method. So Pakistan is probably no exception, and it’s a good guess that it uses RON, too.

    This is not quite accurate, but a simple way to convert from AKI to RON is to add 4 or 5 to the AKI number. You’ll be close enough. The RON number is always higher than its AKI equivalent.

    If the lowest grade fuel available is 92 RON, that’s about the equivalent of putting AKI 87 (regular in most states) in your car. That should be fine if your car was designed to run on it. The owner’s manual should indicate what minimum octane level is required.

  • avatar

    Be wary of octane booster claims, especially that STP stuff….often a bottle of STP raises the effective octane of a full tank of gas far less than it claims. Other “homebrew” octane boosters may actually increase your octane level more, such as Toluene, which is used by a lot of racers here. However, its effect on your 02 sensors and catalytic converters (if so equipped) is questionable at best.

    Oh, and congrats to Sajeev for being the first in the autoblogosphere to use an Amar, Akbar, Anthony reference! Shabash, beta!

  • avatar

    that bullock cart has a better suspension that most GMs….

  • avatar

    He needs to go to Akbar & Jeff’s Octane Booster Hut

  • avatar

    Can we get a fund going to donate and ship some STP to South Asia? I hate to think of the wonderful vtech engines going undernourished. Will somebody please save the Civics?

  • avatar

    jpc0067 is making me channel my inner Helen Lovejoy:

    “What about the VTECs?! Won’t somebody please think of the VTECs!?!”

  • avatar

    I would look and see if you can get some Fuel Power Plus from Lube Control Inc. My understanding is that it will help clean the system from the “rural” fuel you have and help prevent knock.

    Link Here:
    Fuel Power Plus

    full disclosure: I have no affiliation with this company

  • avatar

    Well, Saad, Sajeev, and a few of the commenters, thanks for giving me a great laugh! (Save the Civics!) And reminding me of driving the Peugeot 404 wagon around Europe the summer of ’66, when it would “hump” on the highway. “It’s the bobino,” (coil) said the Italian mechanic. The new bobino did nothing. I can’t remember what other theories were concocted, but my father discovered he could clear the problem for a while by giving the car an Italian tuneup. (Not that he would have ever heard the term, “Italian tuneup,” nor was he one to ever normally drive above the speed limit.

    Once we got the car to the US, the humping ended for good, confirming our theory about the gas in Europe.

    Anyway, good luck Saad, and I hope you have a great trip, with sufficient octane and little need for AC. And yes, another reason why I’m glad to be an American.

  • avatar

    Could someone tell me what Desi means please?

  • avatar


    Its basically any brown person from Asia.

  • avatar

    Thanks Sajeev. I guess that I should have looked it up before asking! For the longest time, I thought it meant “good,” as in Desi Wok, a local restaurant.

  • avatar

    He means South Asia, but not east Asia. At least if Wikipedia is accurate.

  • avatar

    toluene is what you are after

    google toluene in performance engines and you can mix 10% in for higher octane

    been standard for home brew performance fuel for ages

  • avatar
    S. Chaudhry

    Thanks, guys!

    I’ll try toluene sometime. I believe it was Honda who first used it in Formula 1 cars, so should be appropriate in a Civic (I’ll finally know what it’s like to fly down the Hockenheim straight). Won’t it destroy the fuel pump and lines and perhaps even the bore? I’m worried, however, as I recall it is one of the ingredients in TNT. Being in Pakistan, I might find myself in a spot of trouble on suspicion of terrorist intent (I’m kidding, I’m sure the salespeople will be more than happy to sell me some after I promise not to blow anything/anyone up).

    snabster, you’re right. I was (off)road testing a riced-up bullock cart this Sunday (that’s what we drive, right?) and it definitely had better suspension than the last Buick I was in (’01 Century). I’m kidding, again, and I’ve never ridden a bullock cart before. Although, it does give me interesting ideas…

    jpc0067, yes, please! We need to save the Civics!

    Anyway, thanks again. I still think I’ll need to contact Chemistry professors from school if I want to measure octane ratings myself. But I appreciate all the help, and all the laughs.


  • avatar

    If you can find someone with a CFR engine you can measure the octane rating of a fuel. A CFR engine is a variable compression engine specifically designed to test gasoline. They’re not very common and I’ve never encountered one outside of a university.

    If I remember correctly, the RON and MON can be measured on a CFR, the only difference between the two tests is the MON test runs at a faster RPM.

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