308: 91 or 98 Octane??

[RazzaCaine]

hey sorry for the dumb question, im not use to carby cars so was wondering whether i should fill up a vk 308 black motor on 91 or 98 octane? with my old vs v6 i used to just fill it up on 91. will this do the 308 any harm or is it fine to still use 91?

[karlos]

Either but make sure you use the valve lube additive unless the seals have ben done.Compression is only @9.1 so 91 is fine but 98 will be better longterm in regards to carbon build up and econimy to a degree if driven normally.

Thought of using the new BP Ultimate 95octane?

[ari666]

98 and 98 only.

in fact i fill my girlfriends camry on 98. i would fill a scooter on 98 if i had one.

p.s. BP ultimate is 98. premium is 95

[karlos]

98 and 98 only.

in fact i fill my girlfriends camry on 98. i would fill a scooter on 98 if i had one.

p.s. BP ultimate is 98. premium is 95

Sorry if I didnt read your quote correct but are you saying their is no 95Ultimate because servos near me have it and are advertising it as such.The handles even say BP 95Ultimate.

[SL/ENUT]

98, best for it. Also adjust timing a bit, helps out heaps too.

[vkberlina]

hey sorry for the dumb question,

Your right!
This has been covered so many times here before I have done a huge write up on it use the search feature and have a good read.

im not use to carby cars so was wondering whether i should fill up a vk 308 black motor on 91 or 98 octane? with my old vs v6 i used to just fill it up on 91. will this do the 308 any harm or is it fine to still use 91?

As Ari666 said Ultimate 98 ONLY the BP flavour is the best available else other branded 98s will do.

Also Karlos hasnt got a clue on this topic dont listen to him, read my post on fuels and you will know why.

Either but make sure you use the valve lube additive unless the seals have ben done.Compression is only @9.1 so 91 is fine but 98 will be better longterm in regards to carbon build up and econimy to a degree if driven normally.

Thought of using the new BP Ultimate 95octane?

Scott

[karlos]

Your right!
This has been covered so many times here before I have done a huge write up on it use the search feature and have a good read.



As Ari666 said Ultimate 98 ONLY the BP flavour is the best available else other branded 98s will do.

Also Karlos hasnt got a clue on this topic dont listen to him, read my post on fuels and you will know why.


Scott

Now whats your problem reknaw?Elaborate why for us that have no clue please oh high&mighty!

I dont see you quoting Ari666 post on Ultimate95 being incorrect now do I.Be consistant please or just say nothing.

[karlos]

I stated needding the lube for vehicle without hardened valve seats,91 or 98 will work and carbon will build up more on valves/pistons more.95Ultimate is avaliable as an option too.

Its becoming more and more apparent why this forum has nowhere near the numbers(staying and posting)than FordForums,3 words IMPOLITE KEYHAPPY INDIVIDUALS.

[VK SL 3800]

Cmon Karlos just chill, ARI didnt get grilled because all he was on about was octane of petrol and generally premium is 95 and 98 is whatever the retailer calls it. Different retailers call 98 whatever the hell they want, Caltex, im pretty sure is called Vortex for both 95 and 98, shell is V-power for 98 and just unleaded 95 for 95. Its just a name for the fuel after all. Plus you said valve seals instead of seats, but your right by saying 98 reduces carbon.

[ari666]

Its becoming more and more apparent why this forum has nowhere near the numbers(staying and posting)than FordForums,3 words IMPOLITE KEYHAPPY INDIVIDUALS.

lol, smaller community=less douchebags

i apologise if there is a BP ultimate95, was always under the impression that ultimate was their prime brand. bit silly to have 2 ultimates, "this is our ultimate, but THIS is our ultimate"

[DANNY8]

I work at a BP and we have Unleaded 91, Premium 95 and Ultimate 98....and our 2 other BP's are the same.

I run my VK 308 on PULP 95. For 2 reasons, it has stock compression, and we cruise to alot of towns which don't have PULP 98 so wouldn't wanna get it tuned to run on 98 then have to chuck a tank of 95 in and have it pinging all the way home. Prolly wouldn't be that bad, but figured PULP 95 is just a good medium.

[vkberlina]

Ok...
First of all Karlos I have been called worse by better, personal attacks via PM and I quote "You are a deadset wanker but you allready know that. " thanks but keep it out for everyone to read. You might get a little attitude from me on fuel types as every other month we get asked the same question time and time again. Care to look in an owners manual or workshop manual for a VB-VK they were designed for 96 RON Super LEADED fuel. (% Octane with a so called "lead supstitute" is not the same read below as to why. Also I get a little tired of people posting illinformed, misguided information which mislead future readed, well actually maybe not as no one can seem to workt he search function on the forum.

As Danny8 says BP Quote their fuels as follows - If you think I am wrong check their site heres the link BP Australia - Products and Services - On the road - Fuels
Unleaded 95 (Premium)
BP Ultimate (98 Octane/RON)

The problem with forums is people posting misguided, illinformed or wrong information.

In the days of the phasing out of leaded fuels I was doing some contract work at the Shell & Caltex refineries at Kernel, I was building a new engine for my VK and got talking to a couple of petrochemists (I think that was their title) about my concerns and they educated me on what fuels to use. Shell were actually refining BPs Ultimate 98 at the time and the base fuel shell and BP was the same just the final product had a different mix and amounts of additives mixed in at the end. BP & shell had an agreement to refine fuel for each other on opposite sides of the country. This may still be the case today.


For the people who cant search or cant be bothered once again heres my fuels speil - some of the brand names may be incorrect now due to marketing changes etc, but the information is still correct.

Now reasons for running correct octane fuel...

When you run a low or insufficient octane fuel, your engine pinks (detonates, pinking, pings, knock what ever you get the point.) Under load.

Now this causes huge increases of heat in the combustion chamber. Now what this does is causes your exhaust valves to get to point where they begin to melt on the surface. Now generally under high load and/or high-RPM this can/will cause engines to fail.

Now you don’t _have_ to run lead or an upper cylinder lubricant. Under normal every day driving conditions your exhaust valves wont get hot enough (using fuel of sufficient octane) to cause valve seat recession. Even under higher load scenarios this will mostly be the case as well.

I Oz we have had fuels with 98 octane like Shell V-Power and the mobil, BP & Catel Vortex 98 these generally exceed the octane rating for most cars. As you have sufficient octane the car wont pink, because it isn’t pinking you have lower combustion temps so your valves don’t get as hot. As they are not getting, as the valves don’t micro/localise weld themselves to the seats so you don’t get valve seat recession.
note Regular unleaded is around 94 from memory & premium is 96 along with caltex vortex which basically is premium with injector cleaner. V Power, Vortex 98 and the other flavours by mobil & BP are all 98 octane fuels.
Now with the advent of E10 91 octane fuels the problem will become worse, the lower octane ethanol fuel mix burns at much high temps which will cause even quicker valve seat recession. On high performance alcohol cars and rockets water has been used up to 25% mixture to lower combustion temps which could be adapted to a road car. Also fuel mixtures are all wrong so with carbie jetting needs to be changed or EFI computers remapped noral fuel/air ratios are about 14.1 to 15.1, but for ethanol fuels its lower so you need more fuel to the same amount of air to get the same bang, hence the higher fuel consumption on ethanol fuels.

If you drive an older car like a VB-VK and it is driven in a low-stress application, basically used as a daily driver, then you need have no real need to run upper cylinder lubes or lead. As long as you use a fuel that meets or exceeds the octane rating for your engine. Really the only time you hay require an upper cyl lube is high sustained loads and RPM all the time.

If you rebuild your engine the best way to overcome this from ever happening is to install hardened exhaust valve seat inserts and exhaust valves of harder materials, such as 4N stainless.
Also if you lower your compression this will enable you to run a lower octane fuel. Simply retarding your timing isn’t really the proper way to tune an engine to run a lower octane fuel. Although you can advance your timing when you run a higher octane fuel this is because the cars timing was retarded from factory to pass emissions laws etc.

If your car pinks for a longer period of time you may experience pre-ignition or overrun when you turn your engine off. Basically what’s happening is your cylinder is so hot it’s igniting the fuel without the need for spark. This generally wont last long as your engine will destroy itself pretty quick.

The early commodore engine were designed for 97 octane super. If you run 98 octane fuel you wont need to run an upper cylinder lube. Super used to contain approx .14grams per litre of lead, Potassium, Manganese, Sodium & Phosphorus based upper cylinder lubes wont do the same job as leaded fuels, they burn at a lower temperature than lead does. Although they may aid in protecting they wont do the job as well. Sodium based substitues have been linked to damage to turbo charges.
Most additives will also contain a octane booster component. The higher the octane fuel the cooler the compustion temperature will be.


Scott

[RazzaCaine]

vkberlina thank you so much for all that information, it is truly awesome! i'll quarter tank of 91 that is in the car and start filling it up with 98 from now on and now i understand why this should be done. i'll try to avoid asking stupid questions again and will use the search function. to be honest i have no idea why i didnt use it this time, i normally do before asking questions

[vkberlina]

If you really want to do your head in, the changes in octane can also require carbie jetting, injector pulse timings, ignition timing to get the best economy, performance etc. Then with the changes to ethanol based fuels which I feel we will be forced to use in the hopefully distant future throw the tuning out the window due to burn rates of fuel, combustion temp changes again. Talking to a dealership mechanic I know He has done more fuel pumps and fuel system work in the last 12 months than ever before so I guess there will be interesting days ahead.
Also dont use E10 in cars that are rarely driven, boats, aircraft & even lawn mowers (and other garden equipment) the ethanol in the fuel attracts moisture and can cause all kinds of problems from rust in metal fuel tanks, blockages in fuel filters, carbies, fuel rails etc. The water collects in the bottom of the tank and the fuel will sit on top. You can burn the water out by adding metho to the tank which will bind the water and fuel.

cheers
Scott

[DANNY8]

The water collects in the bottom of the tank and the fuel will sit on top.

At work we regularly put a special paste on the dip sticks for the tanks. The paste is to determine if there's any water in the fuels (the paste changes colour if water is present). The instructions for the paste specifically mention to put the paste over a few inches along the dipstick where the fuel level is, as the water sits on top of the fuel.

[vkberlina]

At work we regularly put a special paste on the dip sticks for the tanks. The paste is to determine if there's any water in the fuels (the paste changes colour if water is present). The instructions for the paste specifically mention to put the paste over a few inches along the dipstick where the fuel level is, as the water sits on top of the fuel.

thats interesting I always thought it would collect at the bottom, I have accidently left a plasic fuel drum out in the rain witht he lid off and the water was sitting in the bottom and fuel was on top
Also this link might be useful Petrol - NSW Fair Trading

With the paste do you get to see the water level like half the paste changes and half not wo indicate the amount of water what color does the paste change to?


The pastes we used to use at a servo I worked at for a while used to change color to show water was in the bottom of the tanks. We could see where the exactly how much water was in the bottom

scott

[DANNY8]

This is the gear we use. Not unless I read it wrong. Only used it once or twice (I'm not the person who normally does the checks for water).
Gasoila Chemicals - All Purpose Water Finding Paste

[vkberlina]

Yeah similar product to what we used at shell. We used Kolor Kut. The instructions on their site clearly state Colour changes to yellow at the bottom of the dipstick.... clear indication of water in tank... so it the bottom or end of the dip stick sits in the bottom of the tank the water is in the bottom of the tank.

cheers
Scott

[DANNY8]

Yeah similar product to what we used at shell. We used Kolor Kut. The instructions on their site clearly state Colour changes to yellow at the bottom of the dipstick.... clear indication of water in tank... so it the bottom or end of the dip stick sits in the bottom of the tank the water is in the bottom of the tank.

cheers
Scott

Ah yeah ur right.....which means the once I tried it I done it wrong lol. Our tanks get checked regularly, I just decided to give it a shot one night when I was bored lol. Thx for clearing that up mate lol.