VIC 91RON in V6 Passat

[Khun_tilt]

There are sometimes cases where in the country 95RON and 98RON are simply not available (lucky to get 91RON as most bowsers are diesel).

I know the book says 95RON+ but it also says 91 can be used in emergencies provided driving is at "medium engine speeds" and "high engine load is avoided".

There is no indication of what these limits are. Any hints.

Has anyone driven around the city using 91RON. The service guy had apoplexy when I asked about using it, but my Honda Euro was also speced for 95RON and ran on 91RON fopr 4 years without an issue as the engine management system compensates. In fact Honda service guy said anything above 91 in the city was a waste as engine speed and temperature was not high enough to burn all the octane and it simply went out the pipes.

I also note the Skoda people state the V6 (they use the exact same engine) will run fine on 91RON but may have slightly lower performance.

[h100vw]

You'll notice a drop in performance I reckon. I have run 95 in my chipped S3 and it was crap from the minute I rolled off the forecourt until I filled up with 98 again.

Absolute last resort for me.

Gavin

[Khun_tilt]

Thanks Gavin. Unfortunately I don't have a chipped S3 just a standard V6 Passat.

I don't mind putting 95 in around town where it is usually readily available - the owners manual actually says that any higher than 95 is a waste as there would be no improvement in performance or efficiency - but there are times when only 91 is available such as in country towns and like today when my local servo had a "not in use" sign on both the 95 and 98 pumps and I was hoping someone could tell me the limits with 91 in the tank so as to avoid any possible damage. Like with the space saver tyres when you can only go a certain max speed is it the same if 91 is in the car.

Also I'm now wondering if 80% of driving is in peak hour bumper to bumper would 91 really even make a difference in the city on week days?

[balkanac]

i always use 98 octane in both of my cars. I did fill up the golf with 91 once, it wasnt pulling as hard and it went thru the tank really quickly. so use 91 for emergencies only. 98 burns much cleaner and i have noticed that he engine runs smoother (idle and revs)

[Khun_tilt]

Cheers

At least I know that if caught out in the bush with only 91 available I will at least be able to use it without any damage.

[SMOK3Y]

i even use 98 in my mower & whippersnipper lol

[brad]

the owners manual actually says that any higher than 95 is a waste as there would be no improvement in performance or efficiency -

I would suggest you test this yourself. While I haven't got the V6, my 1.8TSI gets enough fuel economy improvement with 98ron that it is cheaper per km than 95ron.

Take a photo of the decal in your fuel flap - depending on what is written & the size of the numbers, that tells you what fuel you can /can't run.

Personally, If I knew I was going bush, I would fill up with 98ron to offset the lower octane of the ULP (if I had to use it). I would also throw a bottle of octane booster in the boot for emergencies.

The other thing I would do is either load up my GPS with the POIs of the servos that have PULP or install the various fuel companies 'find a servo" apps on my phone.

Given that country running will give you at least 600km (I'd think closer to 800km) before the "Refuel Now!" light comes on (which means you have about 100km left), I can't see how you could get caught out unless you have a fuel card tied to a specific vendor and you insist on running the vehicle down to empty all the time.

[kaanage]

Turbocharged engines (like brad's and Gavin's) would detune more with lower octane than a naturally aspirated engine (like Khun_tilt's V6) since the ECU would mainly cut boost in a turbocharged car while a naturally aspirated engine would mainly have its ignition retarded.

That said, my old Fiat had noticably less power (butt dyno tested) when I had to retard the distributor as the head/piston crowns had carbon build up over time vs when I pulled it down and cleaned all this out (the compression ratio was very high and got too high with the carbon deposits and would ping quite badly). But it was in no way crap.

I know someone who tested 98->91 octane in his Golf MkV FSI and found no difference in fuel economy with normal driving. He did it gradually by part refilling with lower octane fuel to check for pinging/misfires as he stepped down the octane rating - I suggest you do the same.
Obviously, he isn't a road warrior but it suggests that 'normal' driving with your V6 should be fine with the lower octane fuel.

[brad]

Turbocharged engines (like brad's and Gavin's) would detune more with lower octane than a naturally aspirated engine (like Khun_tilt's V6) since the ECU would mainly cut boost in a turbocharged car while a naturally aspirated engine would mainly have its ignition retarded.

No doubt.
The dealer gave me a free tank of fuel about 3 weeks after I bought the car - told me to run my car to empty before coming in...... then they filled me up with 50L of 91ron. My bum-dyno is fairly lousy but the car felt so flat as soon as I drove off the forecourt. As well as cutting boost, I reckon it incresed fuel delivery & retarded the ignition. Never again.

[Khun_tilt]

Would never consider anything less than 98 on a turbo engine. As stated above, it's more than just tuning when they are involved.

I have had several so called "98 only" cars and have never had a problem on the times I put 91 in. In fact the last was a Honda Euro and the head of service at the dealership told me straight out I was wasting my money with 95 and 98 in the city (peak hour mostly) as the engine never got hot enough to actually burn the octane and it just went out the rear. Did 50,000Km on 91 and got enough speeding tickets to say it sure didn't affect performance around town. Long distance freeway driving...well, that's another matter entirely. There was a definate difference when caught with only 91 available.

Just to throw another curly one in for discussion, United sell a 100RON fuel. Theoretically that sounds even better than the 98, right. Wrong. Their 100RON contains 10% ethanol and VW are at least consistent in their statement that ethanol fuel is NOT to be used under any circumstances.

What also should be noted is that in Europe 91 RON has all but disappeared and "standard" is now considered 95; not because cars cannot run on it but 91 was actually more expensive than 95 due to the production process to produce the lower octane. Same in UK wher 91 has totally disappeared - and they have millions of cars that are suited to it. It's another example of how we get ripped off here. If 95 is cheaper to make why are we being charged 13c a litre more than 91? Then again we are the only country where diesel is dearer than petrol too. Of course the ACCC sits on it hands and does nothing.