Is higher octane better?

5388 Views 24 Replies 11 Participants Last post by FormulaDynamics, Aug 24, 2009

QP Sport

Discussion Starter · Feb 12, 2008

Is there an answer for this, by that I mean one which has been scientifically validated? I ask, because in searching this forum and others, there doesn't seem to be a consensus. I know that octane decreases pre-ignition and detonation which I presume is an issue in high compression hot running engines like ours. But if one uses a higher octane fuel (using the same method of reporting, e.g. 91 vs 94 R+M /2 method common in Canada for example) does one

a) get better fuel mileage?

b) improved performance?

c) improved longevity of engine?

The North American manual I believe says to use a minimum 91, but is is worth paying more for 93 or 94 which is reasonably available across NA?

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GrndLkNatv

· #2 · Feb 12, 2008

Higher Octane Fuel

Burns slower, has more energy content per volume but only be taken advantage of by higher compression engines.. Someone running 8.5 to 1 compression won't benefit power or mileage wise from 94 octane versus 89 octane other than the fact that the higher octane usually burns a little bit cleaner but that isn't really a reason to pay for it.

http://www.torquecars.com/articles/fuel-octane-ratings.php

FormulaDynamics

· #3 · Feb 12, 2008

The answer is simple, you only need as much as you really need.

This means that you should only use the recommended octane rating or higher. Higher than recommended will not necessarily get you better gas mileage or more power. It's the fuels resistance to detonate, your stock ECU is programmed for a specific fuel. Anything more doesn't hurt but doesn't help much either, unless you modify your car.

Using too low of an octane rating will cause detonation, costing you power and can eventually damage your engine. Maserati helps protects against this with knock sensors that retard your ignition timing to compensate if necessary.

However there's more to fuel than just an octane number. The quality of fuel is also important. Usually but not always a higher octane fuel will also be a higher quality.

You will also see a bit more power with 100 octane unleaded fuel, but this is not due to the octane rating directly, it also has to do with the oxygenates in the fuel. Never use leaded fuel for anything that has cayalytic converters.

We can program for different fuels, however for the Maserati, 91 is just fine under most any circumstances.

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GrndLkNatv

· #4 · Feb 12, 2008

Shell VPower and AmocoBP Premium

don't have Ethanol added in, it's just gas with their detergent additives.. That for the states, in Australia they do add 5% ethanol and that puts the octane up to 100.. So depending on where you live in the United States, determines what the octane rating of your VPower is.. Here in colorado we 92 and 93 octane available... California is 91, etc.

DeaneG

· #5 · Feb 13, 2008

I mixed in half a tank of 100 with my Calif 91 octane on a whim. Problem is, as you say, there's no practical way to tell the difference on the street. The car does seem faster, but I think it's probably just because my wallet is a lot lighter.

FormulaDynamics

· #6 · Feb 13, 2008

DeaneG said:
I mixed in half a tank of 100 with my Calif 91 octane on a whim. Problem is, as you say, there's no practical way to tell the difference on the street. The car does seem faster, but I think it's probably just because my wallet is a lot lighter.

We can tune for 100 and get few more HP on the dyno but if we don't make the proper adjustments, it's proves to be a fairly worthless investment.

Although, at the shop here in NV we do something similar and blend 91 Octane ($3.39) and 100 Octane ($5.00) to produce a 96 mix. It's great for the street with a chip, produces nearly the same HP as 100 but the cost is much more reasonable.

In Regards to GrndLkNatv's comment:
Sometimes we have to back off our chip timing for regions where they pour in Seasonal additives.

fade2grey

· #7 · Feb 13, 2008

as indicated above, your car is mapped for a range of fuel types - it's configured to correct for say 93-98 using various sensor readings such as knock & lambda etc. If you use a petrol with a higher RON\octaine rating you'll see little or no benifit unless the ECU is re-mapped to use it. In fact, one of the things they do when re-mapping is narrow the band of fuels which can be used in order to release more power.

stats007

· #8 · Feb 13, 2008

UK Maseratis are set to run on what we call Super Unleaded (our 97 and above). At £1.10 ($2) a litre it's getting expensive!

fade2grey

· #9 · Feb 13, 2008

really? My 06 GS says 95 RON on the inside of the flap. (which is a mere 100.1p at my local garage lol)

stats007

· #10 · Feb 13, 2008

Seems odd

- especially as it's a GS. Mine says 97 and it's a 2004MY Coupe GT.

stats007

· #11 · Feb 13, 2008

The manual says

Premium unleaded no less than 95 R.O.N

. Probably makes no difference - I always use Shell V-Power anyway.

Glenn Wallace

· #12 · Feb 13, 2008

One of my race engines was dynoed on 104 and 92, it made MORE power on 92.

It had plenty of compression (10.5:1?) but of course had no detonation issues on 92. So as stated above, no real advantage to higher octane unless your engine tune requires it.

GrndLkNatv

· #13 · Feb 13, 2008

Also remember another reason for high octane....

Which is higher boiling point and less chance of vapor lock. In the aviation industry they run 105 octane low lead and because of altitude they are worried about vapor lock and with the higher boiling point which increases with altitude, they have to run higher octane fuels in conventional engine aircraft....

DeaneG

· #14 · Feb 13, 2008

My CEL has come on for the first time, a couple of days after mixing a half tank of 100 with the existing 91.

Maybe the ECU thinks the knock sensor has stopped working?

FormulaDynamics

· #15 · Feb 13, 2008

Many things may have happened, if you can get a code reader and connect, you'll see what the issue is and clear the code. It may also dissappear on it's own after some time.

I have a code reader that will plug into your laptop for sale if anyone's interested, $100 takes it. It shows you everything a weekend mechanic would need.

Best Regards,
-- Jeff

Toffe

· #16 · Aug 19, 2009

What about ethanol? E10, E85

What about ethanol?

Most Maser drivers would obviously opt for the premium products (vpower, 99, 92 whatever you call it), but now in Europe they are starting to mix in ethanol. There is E10 (10%) rated RON 95 and there is E85 (85% ethanol) for sale in the usual outlets. Carrefour is where I discovered E85.

Does anybody know if it suitable or better has tested E85 on a Maserati? I filled a tank of E10 and didn't see any drop in performance, hear any difference in knock nor did it seem to affect fuel economy. I understand the warnings, "why would you do it", "it might be bad" etc etc, but does anybody know for a fact that its not good? Despite fuel economy being horrendous on Maser's (average 20 liter/100km or 12 US mpg), I do like the potential CO2 benefit for ethanol...

- Toffe

FormulaDynamics

· #17 · Aug 20, 2009

You typically need an ECU adjustment to run Ethanol (E10 should be fine though) because it requires more parts of Ethanol mixed into the air than gasoline. (i.e. yes it's cheaper and not gasoline but you'll use much more of it to go the same distance).

I've tuned Maserati's running on Ethanol in other countries, it can be done.

We've considered coming out with an Ethanol tune but I'm not sure how many Maserati owners would decide to take the plunge and spend extra money to convert.

Best Regards,
-- Jeff

Toffe

· #18 · Aug 20, 2009

Ethanol

>I've tuned Maserati's running on Ethanol in other countries, it can be done.

Can you share any data on this: cost of kit, what needs replacing, fuel economy, performance impact?

>We've considered coming out with an Ethanol tune but I'm not sure how >many Maserati owners would decide to take the plunge and spend extra >money to convert.

Maybe not interesting in the US market, but in Europe is costs USD180 per tank of premium maybe there would be more interest? A tank of E85 would be about USD100. I would convert it if:
1. It was backwards compatible to petrol
2. There was no long term negative effect on engine
3. Apart from having to fill tank more frequently, there was no massive performance hit.

It would make sense for example to fill ethanol when covering a few thousand km of highway, where frequent of filling the tank doesn't matter and you don't need the last 10% of performance. But you should, without penalties be able to switch back to petrol when off the highway.

- Toffe

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Capt. Bluestreak

· #19 · Aug 20, 2009

GrndLkNatv said:
don't have Ethanol added in, it's just gas with their detergent additives.. That for the states, in Australia they do add 5% ethanol and that puts the octane up to 100.. So depending on where you live in the United States, determines what the octane rating of your VPower is.. Here in colorado we 92 and 93 octane available... California is 91, etc.

Not so - here in PA, Shell V Power has ethanol added - I think the fuels are blended differently in different parts of the country, even if the are the same brand and octane number.

FormulaDynamics

· #20 · Aug 20, 2009

Toffe said:
>I've tuned Maserati's running on Ethanol in other countries, it can be done.

Can you share any data on this: cost of kit, what needs replacing, fuel economy, performance impact?

>We've considered coming out with an Ethanol tune but I'm not sure how >many Maserati owners would decide to take the plunge and spend extra >money to convert.

Maybe not interesting in the US market, but in Europe is costs USD180 per tank of premium maybe there would be more interest? A tank of E85 would be about USD100. I would convert it if:
1. It was backwards compatible to petrol
2. There was no long term negative effect on engine
3. Apart from having to fill tank more frequently, there was no massive performance hit.

It would make sense for example to fill ethanol when covering a few thousand km of highway, where frequent of filling the tank doesn't matter and you don't need the last 10% of performance. But you should, without penalties be able to switch back to petrol when off the highway.

- Toffe

Let's say in round #'s that it would cost $2k to convert the system to be ethanol compatible, you would be able to switch back to gas as well.

You'd likely need to empty the tank of one before starting another.

The engine would be safe with the right kit and I don't think that there would be a massive performance hit either. Ethanol does OK, you've just got to fill the tank a bit more often. Perhaps we'd need a bit of testing though to confirm the power difference.

Best Regards,
-- Jeff

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