ulp

[rotorgem]

does anyone use premium or optimax in there gems a few guys have told me it is ok to use ulp in a 1600 with out any mods??

[Benjamin]

PULP is better than ULP. It has a higher octane than LRP which allows you to advance the timing and squeeze a little more performance out of it.
The biggest gains are in driveability and smoothness. Instead of pinging their head off on LRP, a higher spec engine will run nicer on PULP.

I ran ULP in mine once, was just as bad as LRP for a saving of about 2c per litre. Not really worth it.
PULP is roughly the same price as LRP, maybe more expensive at times but I reckon it is worth it.

[Dave]

I use PULP in my Breadvan now exclusively.

It runs so much smoother, has more power and doesn't complain when I fang through the hills bouncing between 4 grand and the red line (6 grand ish).

I used unleaded a couple of times - the stuff is shit. LRP will do the trick if you've got nothing else, but it doesn't even have a similar octane rating to what Super had when the car was new. PULP has a closer octane rating to 1978-spec Super, which is why I use it.

The good news is that Geminis come with hardened valve seats, so there should be no problems with valve seat recession that occurs when you run a normal Super engine on lead-free fuel.

[FrAsErTaG]

I run Optimax And Only Optimax.

[Dave]

But where the Hell do you buy Optimax from? Don't you have to buy it in bulk or something?

I do about 500-700km/week in my car, so I need to be able to buy fuel where and when I want it.

I never use Fox Plus or Liberty. I've heard they're dodgy.

[Andrew]

You get Optimax from Shell servos. I also add the lead replacement stuff you get from Mobil just in case. It costs about 5 cents to treat each litre. Do you guys reckon it's worth it?

[Benjamin]

Either that or find yourself a cheap source of a really light 10W30 or lighter oil and put a little in your tank?

[Pete]

leaded petrol (and LRP) contains lubricants that stop the valve seats from overheating.
I should know, my brother and father both work at shell refinery in sydney.
optimax is a 98 octane.
leaded is a 96 octane
unleaded is a 92 octane.

leaded petrol and optimax are so similar in octanes that there is no possible way that you can notice the difference. Its all in your head!

[Fastgem]

tell that to the detonation

[Mooch]

no probs here with pinging. 100% avgas thank you.

[Dave]

I usually run Mobil PULP (Mobil is closest to my house for a start!) and I can say that the car definitely runs better with PULP that with LRP.

For a start, when I take it up through the gorgeous Adelaide Hills, like I did last Sunday morning, I have it bouncing between 4,000 and 6,250 revs. You can try to do that on LRP, but it really doesn't want to know over about 5,200. Not in my car anyway.

I assume Optimax is just Shells' version of PULP.

Anyway, there should be no need to add lead additives to your fuel. Gemini valve seats are hardened and PULP does the trick fine without it.

[SikGem]

I agree

[Chase]

It is my understanding that Optimax is a more dense fuel which has the effect of giving you a bigger charge sucked into your chamber. It also contains detergents which reduce carbon deposits in your combustion chambers. This l can beleive after pulling down my LC 6 after running it exclusively on Optimax for just over two years, it was noticably cleaner than that of other leaded fuel fed engines.
Anyhow, both my LC and TE are alot happier running on Optimax (l think the difference between Optimax and other fuels is further exasabated as comp. ratio's rise), especially on cool, misty Victorian mornings (higher moisture content perhaps)

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