MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Octane Boosters

I was quite boggled the other day in the auto parts store by the number of octane boosters available and the way in which they could not be compared for effectivness (or claimed effectiveness) in the store. That is, the cans offered no specifics about how much of the additive added to how many gallons of fuel would raise the octane rating how many points. I've never seen anything published about the subject but I assume these additives are at least somewhat effective. Is anyone aware of a comparative test, in a magazine or elsewhere, of octane boosters readily available in the US? Or how about an introductory text about the subject?

Thanks.
Marvin Deupree

Marv,
The December issue of Hot Rod magazne has a short, interesting article which looks at the benefits of octane booster on fuel. While not comparing different types of octane booster, it provides information on the effects of adding the one type, Super 104 Octane Boost, to gasoline. It's a good introduction, and worth a read.

Joe
Joe Ullman

Marvin, if you want to compare between bottles how much octane boost will raise one point, compare 104+ standard bottles to their "better" product line. I believe they have 2 different size bottles with different octane ratings. Thus, one could calculate the effectiveness per ounce of booster. Just a thought.
Jeff.

Jeff Schlemmer

I never believed that horsepower could ever come from a bottle {'ceptin nitrous....) until I used 104+ and I was really impressed with the stuff. I tried a bottle after pumping in 10 gallons of cheap gas from a 2 pumper up in the mountains; the idle smoothed, the pinging stopped and i noticed a definite seat of the pants increase in off idle power about 2 minutes after adding the booster. I let the tank run all but out before refueling with 93 octane gas, and there was very little change in performance. I tried another bottle of 104 and it made the 93 octane gas come alive under hard throttle. Only prob is it's too expensive to run all the time...
Mark Childers

Most so-called octane boosters are little more than a fuel additive, which remove carbon deposits and generally clean up your fuel system. Strictly speaking, they do not up the octane of your fuel (the claims are blatantly deceptive and require a whole lot of reading between the lines). They at best only reduce the octane requirement of your engine by reducing the compression ratio. These are potentially of benefit for older engines where that is the problem. Of course, if you have no carbon deposits they are of no use at all. Every octane booster I have ever seen on the shelves of every parts store has been of this type (STP, 104 plus, Super 104 plus, and all the rest). Those products don't spell out any increase in octane of the fuel because there isn't any. They sometimes make some fluffy claims about effective octane increases - which are meaningless because they clearly have no way of knowing how much carbon you have in your combustion chamber! The only REAL fuel octane booster I have ever located and made clear sense of the increases in fuel octane was at a speed shop at 8 bucks a can to treat about 20 gallons ( I can't recall the brand name right now - I'll check on that).

After installing a new high compression motor I wanted (needed) to run higher octane fuel. Using 93 octane from the pump, at first I found that only the expensive real octane booster worked to stop pre-ignition. But one exception is Knock-Out. It is a few bucks a bottle and has definitely stopped pinging (pinking), but I can't figure out why it works when it seems just like all the other bogus products with the same ambiguous claims. I know it is working to stop pre-ignition, so I can only assume it truely ups the octane since that is the definition of octane. One clue may be the admonishment on the bottle that it is for off-road use only! ;)

I recall seeing a great website somewhere which spelled out the true nature of octane and why it doesn't do what many people think it does (that is, it does not give you any more power aside from allowing you to optimise your ignition advance). Maybe someone who has seen it too has that site location.

Dean
Dean Lake

Here is a good start on what you want to know about octane boosting chemicals:

http://members.aol.com/prschekllr/octane.html

(may have to cut and paste URL in your Browser window..)

Dave
Dave Munroe

Here in the UK we have a Trades Descriptions Act under which claims made for a product have to be demonstrably true (which is why magic tin pellets and magnets that make your engine unleaded can't be advertised here). Castrol sell two versions of unleaded petrol treatment - one without octane booster and one with. Castrol's own literature only claims 'an octane boost' which could be taken to read one octane, but some suppliers claim it raises octane by two. My experiences are that 95 octane with the octane boost gives very much worse pinking and running on than 97 without. Shell Optimax with unboosted valvemaster gives results at least as good as 4-star leaded.

The link above says "12-16 ounces will only raise octane 2-3 *points*, I.e. from 92 to 92.3" 12-16 ounces in how much? A gallon? A tank? Castrol treatment rates are 1ml per Litre i.e. 1 part in a thousand.

PaulH.

Paul Hunt

Try some aviation fuel. Mix it 1/4 av gas to 3/4 pump gas. I will make for a REALLY FUN ride.
Dave Pearn

So a bit of a continuation of this subject. I believe it states in the manual of the MGB to run 98 Octane gasoline. Is this the same 98 rating as I see on my pumps or a different (i.e. Imperial?) rating? To make matters even more difficult, here in California they have recently lowered our top grade to 91 octane.

What exactly is it with these engines that they require such a high octane gas? My Honda has higher compression but works fine with crap gas. I even drive by the station in the MG and it starts running rough. I would say this is the only thing that irritates me about this wonderful little car. I had no idea that I would have to use Premium.

Thanks in advance.
Jason
1970 mgb roadster
Jason Coolbaugh

Jason:

The trick is in the combustion chamber design and the piston that fits into it. If you can adjust the mixture and timing on the fly, that too will help.

Modern combustion chamber design uses tools (really big computers) that were not available to MG designers.
For that matter, neither were the onboard computers that sense knock and then adjust timing and mixture. And lastly, the Japs seem to be brillant at engine designing; the Brits, well I am not so sure...;)

Pete
Pete

Jason;

There are 2 different methods to measure octane rating of fuels. One method produces a Research Octane Number (RON) and the other method produces a Motor Octane Number (MON). For the same fuel, these two methods will produce octane numbers that are about 10 points apart (i.e., the RON method will read 98 and the MON method will read 88). In the U.S. refiners and retail gasoline sellers are required to use the average, which is why you always see the formula (RON + MON)/2 below any octane number.

Now, as to the octane rating shown in your owner's manual. European gasoline used to be rated only by the RON number, thus it will be a higher number in the owner's manual. Therefore, the 98 rating in your owner's manual is equal to 93 octane U.S. gasoline. Depending on where you live, you may be able to find that level of octane at the pump (I believe that Sunoco sells a fairly high octane premium unleaded). The use of 91 vs. 93 won't make any significant difference, but you should make sure that the engine is kept in top tune at all times (which isn't a bad idea for any engine).

One thing you can do is to fill up your tank early in the morning when it is cooler and the muffler has not heated up the gas tank. Hot weather and/or a warm gas tank will drive off some of the volatile components in gasoline, which help the octane rating. This is the reason you see drag racers cooling their fuel before a race since they are using very volatile components.

If you are tempted to try out some of the custom mix octane compounds listed in the referenced website, then take the time to check compability with your fuel system components. Toluene and Xylene are very powerful solvents (which is why the make great paint cleaners and strippers) and can dissolve some rubber and plastic compounds in a matter of hours. If you really want to try using these as octane boosters, then buy pieces of all your rubber and plastic components in your fuel system and place them in a small covered container of the solvent and leave sitting. If there is no change in a week in the state of the components, then you probably have compatible materials.

Lastly, please remember that Toluene and Xylene are extremely flammable and can ignite at very low temperatures. If I can remember right, the energy in a pint can of either solvent is equal to a stick of dynamite. And in order to get any significant octane boost you need to mix gallons of this stuff.
Ron Kluwe

Not just modern engines. The V8 runs on just about anything without pinking or running-on. Whereas the roadster is very sensitive to advanced ignition and always runs on even on UK 97, 98 or 99, both are much worse on UK 95.

PaulH.
Paul Hunt

Thanks for your comments, gentlemen.
I went to the local Barnes & Noble to look for the Hot Rod Magazine cited. They didn't have it but it still took me about an hour and $65. to get out the door.
I did some web surfing and could find nothing which really addressed my original posting but did find some interesting info. Check into www.osbornauto.com and click "Racing Fuel"; there is info on various racing fuels marketed by 76 Oil Co. (including a 100 Octane unleaded, street legal gas), the RON/MON business, and aviation gas. There is an item about "Octane Determination in Piston Engines" which I found to be good background info at www.prime-mover.org/Engines/GArticles/octane.html. Most of the websites for the octane boosters didn't offer any more info than appears on the back of their cans.
The recipes in Dave Munroe's reference appear in several websites. But if I decide to take up home brewing it will be with something less volatile, like beer.
I have yet to investigate racing fuels in my area. I can get Sunoco pump gas at 94 octane and I believe Amoco also offers a 94; other than that, 93 seems the best we can do around here. My stock '67 BGT does OK with the 93 but my MGA, which has a CR of about 9.4:1 pings something awful. I think I will start a "buy-em-and-try-em" research project on the boosters. If I find a magic elixer I'll post it here.
Marvin Deupree

Morning Folks,

Interesting chat on Octane and the various approaches.

My read on Octane is that it is just a measurement of "resistance to ignition". There seems to be no extra power, cleaning ability or any other factor provided with an increase in octane rating except it slows the burning process - so effectively stops preignition problems.

For this reason, burning anything above the necessary Octane rating should be a waste of money. Running with less rating than needed will result in our familiar pinking and eventual significant engine damage.

That being said, why can't we just add water to slow down the combustion process? :^)

Here's a small website that may be of interest: http://www.ftc.gov/bcp/conline/pubs/autos/octane.htm

Joe
Joe Lucas

This thread was discussed between 16/11/2001 and 25/11/2001

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.