95Ron Or 98Ron - That Is The Question...

[Alfa156Melb 9]

Guy's I'm looking for opinions, or better yet, facts :Big Grin:

 

I was reading a thread over in AO where one of the more reputable members advised a 156 TS owner that some of his engine pinging problems may be attributable to using 98RON fuel. His premise was that as 98 burns hotter so it might be burning his valves over time, thereby causing a pinking noise.

 

Here's the thread - http://www.alfaowner.com/Forum/alfa-147-156-and-gt/369203-2-years-of-engine-pinking-noise.html

 

It's said in this thread that the car cannot 'tell' the difference between 95 and 98 because the spark cant advance any more than which is required for 95.. so anything above that (for a healthy engine) is unnecessary.

 

Which brings me to my conundrum.. I have almost always used 98RON, most people in forum land are evangelistic about it, also as the JTS has a higher compression so it made sense to use it.

 

Another good reason is that they tend to coke up a little (lot) thanks to the direct injection so the extra soap in the fuel might help - on the other hand, given its direct injection - the fuel doesn't swish around behind the inlet valves so - moot point.

 

Anyway - 98RON is expensive.. So, is there really any advantage to 98RON over 95RON in our JTS's?

[Morgan 46]

I can't comment on the Alfa JTS engine specifically, though when it comes to using high-end fuels, I've always run my cars on the fuel that suits the engine best (in terms of smoothness, economy, performance, etc.)

 

For instance, many moons ago, I had a P10 Nissan Primera 2.0 eGT, which ran like a dog on 95, but like a dream on 98.

 

Conversely, my E38 BMW 740i ran beautifully on 95. There was no difference whatsoever when using 98 in that car.

 

My advice would be to test 95 and 98 back to back. If you can't tell the difference, stick with 95.

[twisted_pr 16]

My old Mk2 Golf GTI ran like a dream on 99RON (Shell V-Power) and OK on standard 95RON, so I used to fill up with 99 wherever possible. May have something to do with the engine initially being designed for leaded fuel, and then adapted for unleaded? Conversely, I can't really tell the difference in my 147 2.0TS, so now use 95 as it's less expensive (somehow "cheaper" is the wrong word) than the 99.

 

In his Shell video post, Mr Smaky said go for 98 in a JTS, as that's what the engine management is expecting - http://www.alfadriver.com/forum/index.php/topic/3772-best-fuels-available/

[Smaky 73]

The engines were designed and tested using V-Power, the maps are adaptive to take this sort of thing into account, but chopping and changing between 98 and 95 will confuse the ECU over time and running the engine with the different charecteriatics of the fuels will in time heat treat the internals in different ways.

 

The slower burning 95 actually makes the engines run hotter than 98 as the 98s more explosive burn speeds up the flow of gases through the cycle and this faster flowing gas keeps things more stable in the temerature range which protects the valves and seats. My choice is 98 Ron and as this is a debate which will go on, I think it best to run the car as it was designed and tested.

[Alfa156Melb 9]

Sounds fair, thanks Smaky.

[twisted_pr 16]

How come standard petrol has to be 95 RON, whereas the super-grade rocket fuels can be anywhere from 97 (BP) to 99 (Shell & Tesco)? That can't help the car manufacturers.

 

Also, Johnny Foreigner standard petrol can be as low as 92, with V-Power rated at 95 (Netherlands, Germany) and V-Power Racing rated at 100 (Germany). Confusing. So do manufacturers carry out engine tests in each country and produce a bespoke map for that country, or do they just do one test and one map per continent (eg Europe) and how do they decide which RON to use? Or do the ECUs adapt?

[Morgan 46]

My Bimmer 7-Series (E38) had a label on the inside of the fuel flap that said "USE ONLY 88-99 RON".

 

It would basically run on anything from jungle juice to Shell's finest. Bloody clever, those Germans.

[Smaky 73]

How come standard petrol has to be 95 RON, whereas the super-grade rocket fuels can be anywhere from 97 (BP) to 99 (Shell & Tesco)? That can't help the car manufacturers.

 

Also, Johnny Foreigner standard petrol can be as low as 92, with V-Power rated at 95 (Netherlands, Germany) and V-Power Racing rated at 100 (Germany). Confusing. So do manufacturers carry out engine tests in each country and produce a bespoke map for that country, or do they just do one test and one map per continent (eg Europe) and how do they decide which RON to use? Or do the ECUs adapt?

 

Some manufacturers have alternate maps for markets, Belgium and South Africa are common ones, others sometimes have a flip round plug so that it connects an alternat circuit depending on the fuel in the region and nowadays most havea wideband map which can adjust itself using the numerous sensors to perform best, but most will be testing with 98/99 RON to get the highest power figures for the sales brochure.

[twisted_pr 16]

Thanks Smaky. Think I'll go back to 99 V-Power on next fuel up - double points 'n all.

[Sphinx 7]

My Bimmer 7-Series (E38) had a label on the inside of the fuel flap that said "USE ONLY 88-99 RON".

 

It would basically run on anything from jungle juice to Shell's finest. Bloody clever, those Germans.

So basically it said "use only petrol. Diesel might slow it down a bit."

I'd hate to drive something running on less than 88 ron...

[celadon 0]

What fuel does it say to use in the handbook ??

 

Mine originally had to be 95RON, but since the re-map, should be 97 or above, and runs much better on higher octane fuels.

 

I also get more miles out of a tank of fuel using higher octane fuels.

[smiffy 99]

Snap if I use crap supermarket stuff the gta runs terrible, if I use the high octane stuff it's loads better and like you said more miles

[K9d 108]

I've tried Ultimate diesel in my 156, made sod all difference.

 

I will try better stuff in my 166 at the next fill up to see if it makes a difference.

[Gibot123 16]

My 24v 164 runs fine on 95 but does feel a bit more free when I have used 99 V power.

147 not sure it makes any difference. Certainly not as noticeable as the busso.

Edited September 17, 2013 by Gibot123

[K9d 108]

Fortunately I won't have to wait long to fill up the 166

 

won't waste it on the Sele, since Kathy claimed ownership it doesn't get used the same.