of 996 ownership (best 2 months of car ownership ever !!) I still have a couple of questions that the answers seem to be eluding me.

Maybe this is a bit more of a poll, then looking for advice...regardless, answers from the experienced masses generally prove to have validity...and yes, I have gone through countless hours of threads searching for my holy grail of answers, but, I shall ask anyway...

1. I have been running of Sunoco 94 (car is daily driver)....any benefit on using this vs. say, Shell V Gold ??

2. just how many kilometres should I expect from a tank when driving civil (ie. not shifting near redline everytime just to hear the exhaust open up and cruising at a casual 110 kph when on the highway) ?? (some discussions have said that it is unusual to see 400km from one tank, whereas others have said that a mix of calm and sedate city and highway driving has seen almost 600km from a tank)

I almost saw 475km from my last tank but that was with a lot of highway driving with my 4 ways on.

its not that I'm overly concerned (if I was then I would certainly not have bought this car as my commuter DD)...just curious as to what I should reasonably expect.

Colin

 

I can only answer your first question. Sunoco Gold has a little more octane than Shell. A high octane allows you to run a higher compression than a lower octane, but doesn't translate into more hp necessarily without the increased compression. Also the ethanol in Sunoco fuel disolves particulate matter from the gas station's tanks and collects water (particularly if not driven regularly) in your own tank. (I think I posted this somehere else recently). A master tech at my BMW dealership says he gets about 1 car a week with fuel system problems arising from this very thing.

Save your money and get Shell Gold. It's better fuel.

 

1. Sunco 94 burns cleaner but is not better for performance or the engine. It is better for the enviroment. Shell 91 is the best performance gas we can get.

2. Driving and taking it easy I get 9-10 L / 100 km with a 60 L tank I could get 600 km of hwy driving. Normally I get 15-16 L / 100 km driving it hard and rarely seeing below 3k rpm which a is about 375-400 km.

 

Really? I never knew Shell 91 had better performance. What's the performance difference?

When I raced Motorcross I always did my two stroke mix with Sunoco 94, same with 65% of the other guys as we couldn't afford race gas. But I am positive I could feel the difference between 91 & 94, with 91 the bike vibrated more and ran a little rougher it seemed.

Sorry, back to your thread!

 

Sunoco 94 gets the rating from the 10% ethanol they add to the gas. Ethanol absorbs water and mixes with it much more easily then gasoline. Unless you have an engine designed to run off Ethanol it doesn't provide any performance and more then likely degrades it. Also I've went though a set of catalytic converters every year I used Sunoco 94. Now that I only run Shell I haven't had an issues since.

 

The octane requirements and burn rates are different for a 2 stroke engines which also revs alot higher.

 

I drove to Montreal from Mississauga almost 575KM on Sunoco 94... 1 Tank... dint stop for Gas, cruised at 120kmph... i get no more than 300km when i Terrorize the street of Mississauga

 

I was told by someone that knows, that my turbo Porsches do get more power from sunoco 94.
Brad the ethanol may have only been added in recent years to the 94, and perhaps not when you were doing motocross.

 

I run Shell v-power 91 too. Less (or no) black soot on the exhaust tips versus Sunoco 94. Observed fuel mileage:
highway at 120-130 km/h= 9.5l/100
Daily driving: 13.5l/100
Trackday= 19-21l/100

 

Looking through my Porsche manual thay state to basically stay away from fuels that contain ethanol. I believe the ethanol is what's added to bring up the octane in Sunoco 94. I used to run an older Mustang turbo with Sunoco and it proved to be the best at controlling predetonation. The best was going out to Competition Fuels in Mississauga with tons of jerry cans and buying av-gas. The car was incredible running on that stuff even at double the price.

My mechanic suggested not to run Sunoco 94 but Shell 91 with an octane supplement as the Shell base fuel is much better than the Sunoco stuff. I'm not sure a non turbo car would benefit from higher octane unless it's a high compression motor however, I'm 100% sure that a turbo car needs it like we need air to breathe.

 

On average I get 380 - 410km a tank on my summer DD (996). 600-700km in my winter DD (Passat)

 

Is your Passat 1.8T 5 Speed? i can bearly make out of 600KM on a full tank and its mostly Highway Driving.. mine is a 03 1.8T Auto

 

With regard to Sunoco 94, unless your manual asks for that octane (which would be really unusual) there is no benefit. Modern engines with knock sensors will detect and adjust for lower than specified octane, allowing you to safely use, say, 87, although with a degradation in performance. However, the engine control system won't make adjustments for anything with a higher octane than whatever the manufacturer recommended.
For modified cars it is a different story (maybe)
The chip might be programmed to take advantage of (or even require) higher octane. However, if there is no detonation present, there is absolutely no gain from higher octane. The problem is figuring out whether there is detonation.
I found out on a hot day at a long track with 91 octane fuel - detonation caused three piston rings to break.
In my case, my chipset is programmed for 94 octane - it has a fairly agressive amount of ignition advance, just below the detonation point. The higher octane provides some safety barrier against detonation in case the mixture leans out (I made three trips to a chassis dyno measuring air/fuel ratio to get the programming right), or if it gets hot ( a bigger problem with air cooled engines).
All of this applies whether the engine is normally aspirated or turbocharged, although turbo engines need the detonation safety margin because it is so easy for the inlet air temp to rise if the intercooler loses effectiveness when it is warm out.
My car has had a steady diet of Sunoco 94 for more than 10 years, and 100K km, with no apparent ill effects.
regarding km/tank - I can get 900 KM out of a tank in my Avalanche, on the highway.

 

But Bob aren't turbo engines usually significantly lower in compresion ratio when comapred to N/A engines ? this should help in pre detination should it not ?

 

how big is the tank in the Avalanche?